19 Nov
2001
19 Nov
'01
9:11 a.m.
I have a complete TRS-80 Model I that has a dead Western Digital FD1771-01
chip in its expansion interface. Does anyone know if a National 1771-B01
is a suitable replacement? What would be a fair/reasonable price for a new
1771 these days?
-Toth
19 Nov
19 Nov
11:11 a.m.
You can get one for cheap if you go down to the thrift store and buy an old
TRS-80. That will cost less than a new WD1771, I'd bet.
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, November 19, 2001 1:11 PM
Subject: 1771 floppy controller questions
I have a complete TRS-80 Model I that has a dead
Western Digital FD1771-01
chip in its expansion interface. Does anyone know if a National 1771-B01
is a suitable replacement? What would be a fair/reasonable price for a new
1771 these days?
-Toth
7:39 p.m.
On Mon, 19 Nov 2001, Richard Erlacher wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
That conflicts with my ideals and goals on collecting/repairing these
machines. The expansion interface for the model I also seems to be
somewhat hard to find, as I haven't seen one in a thrift store in quite
some time. The model 3 and 4 have a different 1771, which I seem to
remember is not an exact replacement.
This particular TRS-80 was given to me by its original owner some years
back before he passed away. We had made plans for me to to pick up even
more old stuff to go with it, but he died before that happened.
-Toth
I have a complete TRS-80 Model I that has a dead
Western Digital FD1771-01
chip in its expansion interface. Does anyone know if a National 1771-B01
is a suitable replacement? What would be a fair/reasonable price for a new
1771 these days?
You can get one for cheap if you go down to the thrift store and buy an old
TRS-80. That will cost less than a new WD1771, I'd bet.
9:41 p.m.
The model 3 has a 1793, which is very similar, but not identical. The 1771 has
an inverting data bus, and the MFM-capable version with an inverting bus is the
1791. I do believe I saw a message that indicated that BG Micro has the WD1771
for $4.95. I doubt there's a version that wouldn't work in the Model 1.
You're right, in that the model 1 expansion box is not a really common item.
I've not seen one in quite a while. They've probably gone to the great beyond
by now. The 1771 was quite popular, and had several second-sources, so perhaps
the NS part is worth a try. In the Model 1's single-density application, almost
any 1771 should work fine, though working fine doesn't really mean working
reliably. What I'd suggest is that you synchronize the data from the drive with
the 1771 by interposing a pair of 74HCT74's between the FD data in (after the
schmidt trigger) and the 1771, clocked with the fastest harmonic of the FD clock
that you can find on board. That forms a dual-rank register and synchronizes
the data in a way that has a good chance of improving the system performance.
You might confer with Tony Duell, as he's apparently persuaded the M1 FDC to
work fairly well. An upgraded data separator was quite a popular enhancement.
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, November 19, 2001 11:39 PM
Subject: Re: 1771 floppy controller questions
On Mon, 19 Nov 2001, Richard Erlacher wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
That conflicts with my ideals and goals on collecting/repairing these
machines. The expansion interface for the model I also seems to be
somewhat hard to find, as I haven't seen one in a thrift store in quite
some time. The model 3 and 4 have a different 1771, which I seem to
remember is not an exact replacement.
This particular TRS-80 was given to me by its original owner some years
back before he passed away. We had made plans for me to to pick up even
more old stuff to go with it, but he died before that happened.
-Toth
I have a complete TRS-80 Model I that has a dead
Western Digital FD1771-01
chip in its expansion interface. Does anyone know if a National 1771-B01
is a suitable replacement? What would be a fair/reasonable price for a new
1771 these days?
You can get one for cheap if you go down to the thrift store and buy an old
TRS-80. That will cost less than a new WD1771, I'd bet.
10:46 p.m.
On Tue, 20 Nov 2001, Richard Erlacher wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
I figured the model 3 used the same controller as the model 1, but it
makes sense that they changed that part of the design. I own both a model
3 and 4, neither of which currently work. Any ideas on where a service
manual can be found for either of these? I also have a model 2 that worked
the last time I pulled it out, tho I'd like to find a manual for it too,
since I imagine I will have to service it at some point in the future.
On Mon, 19 Nov 2001, Richard Erlacher wrote:
The model 3 has a 1793, which is very similar, but not identical.
The 1771 has an inverting data bus, and the MFM-capable version with
an inverting bus is the 1791. I do believe I saw a message that
indicated that BG Micro has the WD1771 for $4.95. I doubt there's a
version that wouldn't work in the Model 1. You can get one for cheap if you go down to the
thrift store and buy an old
TRS-80. That will cost less than a new WD1771, I'd bet.
That conflicts with my ideals and goals on collecting/repairing these
machines. The expansion interface for the model I also seems to be
somewhat hard to find, as I haven't seen one in a thrift store in quite
some time. The model 3 and 4 have a different 1771, which I seem to
remember is not an exact replacement. You're right, in that the model 1 expansion box is
not a really common
item. I've not seen one in quite a while. They've probably gone to
the great beyond by now.
Kinda sad too, I used to see this kind of gear in the resale shops all the
time. Over the last 4-5 years, very little of it seems to be showing up in
the places I used to see it in.
The 1771 was quite popular, and had several
second-sources, so perhaps
the NS part is worth a try. In the Model 1's single-density
application, almost any 1771 should work fine, though working fine
doesn't really mean working reliably.
I've heard a few stories about reliability problems with the expansion
interface's floppy controller. I sure hope not all of them were true ;P
What I'd suggest is that you synchronize the data
from the drive with
the 1771 by interposing a pair of 74HCT74's between the FD data in
(after the schmidt trigger) and the 1771, clocked with the fastest
harmonic of the FD clock that you can find on board. That forms a
dual-rank register and synchronizes the data in a way that has a good
chance of improving the system performance. You might confer with Tony
Duell, as he's apparently persuaded the M1 FDC to work fairly well.
An upgraded data separator was quite a popular enhancement.
The original owner of this model I did add an external data separator
board between the expansion interface board and the 1771. Would that board
have provided a similar circuit?
-Toth
20 Nov
20 Nov
1:18 p.m.
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10:18 p.m.
On Wed, 21 Nov 2001, Tony Duell wrote:
It has been a number of years since I powered them up. Right now I think
they are both sitting disassembled in a couple of large boxes. I'm in the
process of construction of a building just for my old hardware, so once
that is done, I'll pull both of them out and bench them and see what their
problems were. I think the model 3 would start up, but just plain lock up
about the time it was going to boot. I think it may be a ram problem. The
model 4 didn't power up at all if I remember correctly.
-Toth
makes sense
that they changed that part of the design. I own both a model
3 and 4, neither of which currently work. Any ideas on where a service
manual can be found for either of these? I also have a model 2 that worked
I have at least schematics for the M3 and non-gate-array M4. What's the
problem with your machines? What do they do at switch-on?
21 Nov
21 Nov
9:13 a.m.
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9:46 a.m.
For troubleshooting possible RAM problems, it's really easy simply to hook a
64Kx8 SRAM on top of the DRAMs, grabbing the addresses before the decoder and
multiplexers, and use OR'd nCAS to the DRAMs as the output enable to the SRAM.
You simply disable the data from the DRAMs by pulling the pins out of the
sockets. The result is that your system works using the SRAM, yet you can poke
around all you like in the DRAM array and the associated timing logic.
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Wednesday, November 21, 2001 1:13 PM
Subject: Re: 1771 floppy controller questions
When yopu have time to get them out again, let us know (or let me know),
and we can discuss troubleshooting them.
>
> On Wed, 21 Nov 2001, Tony Duell wrote:
>
> > > makes sense that they changed that part of the design. I own both a
model
> > > 3 and 4, neither of which currently
work. Any ideas on where a service
> > > manual can be found for either of these? I also have a model 2 that
worked
I have at least schematics for the M3 and non-gate-array M4. What's the
problem with your machines? What do they do at switch-on?
It has been a number of years since I powered them up. Right now I think
they are both sitting disassembled in a couple of large boxes. I'm in the process of construction of a building just for my
old hardware, so once
that is done, I'll pull both of them out and bench them and see what their
problems were. I think the model 3 would start up, but just plain lock up
about the time it was going to boot. I think it may be a ram problem. The
Mybe RAM. Most disk problems on the M3 and M4 are either the 1793 chip
(I've had to replace a couple) or more likely that infernal ribbon cable
between the CPU board and the disk controller. If you don't care about
your machine being unoriginal, you can use 40 way IDC cable and
connectors to replace it (just use 1 row of pins in the connector to
replace the 20 pin SIL socket on the CPU board or disk controller).
You're only using 20 wires in the cable, which is something of a waste,
but it's the easiest fix I've found [1].
model 4 didn't power up at all if I remember
correctly.
In which case check the outputs of the power supplies -- both of them --
before doing anything else.
[1] For the HP97 owners on this list, 26 way IDC cable/connectors and pin
headers can be made to replace the ribbon cable between the logic board
and the card reader. It cures a lot of card reader problems :-)
-tony
12:43 p.m.
On Wed, 21 Nov 2001, Richard Erlacher wrote:
From: "Tony Duell"
<ard(a)p850ug1.demon.co.uk>
I bought a used dip style dram tester set about a year ago. It only cost
me $5, and I figured it might be useful for testing all the old 64k and
256k drams I seem to run into in old pcs. I haven't yet had a chance to
use it yet. Maybe it will help with these old boxes...
-Toth
Mybe RAM. Most disk problems on the M3 and M4 are
either the 1793 chip
(I've had to replace a couple) or more likely that infernal ribbon cable
between the CPU board and the disk controller. If you don't care about
your machine being unoriginal, you can use 40 way IDC cable and
connectors to replace it (just use 1 row of pins in the connector to
replace the 20 pin SIL socket on the CPU board or disk controller).
You're only using 20 wires in the cable, which is something of a waste,
but it's the easiest fix I've found [1].
For troubleshooting possible RAM problems, it's really easy simply to hook a
64Kx8 SRAM on top of the DRAMs, grabbing the addresses before the decoder and
multiplexers, and use OR'd nCAS to the DRAMs as the output enable to the SRAM.
You simply disable the data from the DRAMs by pulling the pins out of the
sockets. The result is that your system works using the SRAM, yet you can poke
around all you like in the DRAM array and the associated timing logic. 
8:18 a.m.
Date: Wed, 21 Nov 2001 17:43:18 -0600 (CST)
From: Tothwolf <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Subject: Re: 1771 floppy controller questions
Reply-to: classiccmp(a)classiccmp.org
I bought a used dip style dram tester set about a year
ago. It only cost
me $5, and I figured it might be useful for testing all the old 64k and
256k drams I seem to run into in old pcs. I haven't yet had a chance to
use it yet. Maybe it will help with these old boxes...
Does work great but I like the kind that allows you to stress DRAM by
"overclocking" beyond it's speed rating by twisting that knob.
Example, that part fall over at just 3ns over rated speed, naah
plonk! It will fail running warm anyway when machine is closed up.
Only limitation it only works w/ 256K and 1M, 1 bit and 4 bits.
Cheers,
Wizard
-Toth
11:57 p.m.
On Wed, 21 Nov 2001 jpero(a)sympatico.ca wrote:
This may be the set I found. It has a checker and a speed verifier. I
guess I should pull them out and see just what kinds of chips they work
with. I didn't expect them to work with 1M chips, based on how old they
looked, but if thats the case, they may not be usable for the 64k chips I
was hoping to use them with.
-Toth
From:
Tothwolf <tothwolf(a)concentric.net>
I bought a used dip style dram tester set about a
year ago. It only cost
me $5, and I figured it might be useful for testing all the old 64k and
256k drams I seem to run into in old pcs. I haven't yet had a chance to
use it yet. Maybe it will help with these old boxes...
Does work great but I like the kind that allows you to stress DRAM by
"overclocking" beyond it's speed rating by twisting that knob.
Example, that part fall over at just 3ns over rated speed, naah
plonk! It will fail running warm anyway when machine is closed up.
Only limitation it only works w/ 256K and 1M, 1 bit and 4 bits.
1:40 p.m.
You'll want to be careful with the early DRAMs, as they used 3 supply rails, and
your tester of 5-volt-only DRAMs may die from application to a 3-supply DRAM.
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Wednesday, November 21, 2001 4:43 PM
Subject: Re: 1771 floppy controller questions
On Wed, 21 Nov 2001, Richard Erlacher wrote:
> From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
>
> > Mybe RAM. Most disk problems on the M3 and M4 are either the 1793 chip
> > (I've had to replace a couple) or more likely that infernal ribbon cable
> > between the CPU board and the disk controller. If you don't care about
> > your machine being unoriginal, you can use 40 way IDC cable and
> > connectors to replace it (just use 1 row of pins in the connector to
> > replace the 20 pin SIL socket on the CPU board or disk controller).
> > You're only using 20 wires in the cable, which is something of a waste,
> > but it's the easiest fix I've found [1].
>
> For troubleshooting possible RAM problems, it's really easy simply to hook a
> 64Kx8 SRAM on top of the DRAMs, grabbing the addresses before the decoder
and
> multiplexers, and use OR'd nCAS to the DRAMs
as the output enable to the
SRAM.
> You simply disable the data from the DRAMs by
pulling the pins out of the
> sockets. The result is that your system works using the SRAM, yet you can
poke
around all you
like in the DRAM array and the associated timing logic.
I bought a used dip style dram tester set about a year ago. It only cost
me $5, and I figured it might be useful for testing all the old 64k and
256k drams I seem to run into in old pcs. I haven't yet had a chance to
use it yet. Maybe it will help with these old boxes...
-Toth
22 Nov
22 Nov
12:20 a.m.
On Wed, 21 Nov 2001, Richard Erlacher wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
Thanks for the warning, I'll make sure to double check the datasheets
before I try to test chips with it. I guess if I have to, I could make an
adapter of somesort to test older chips too...
-Toth
I bought a used dip style dram tester set about a
year ago. It only cost
me $5, and I figured it might be useful for testing all the old 64k and
256k drams I seem to run into in old pcs. I haven't yet had a chance to
use it yet. Maybe it will help with these old boxes...
You'll want to be careful with the early DRAMs, as they used 3 supply
rails, and your tester of 5-volt-only DRAMs may die from application
to a 3-supply DRAM.
8:56 a.m.
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2:51 p.m.
I was concerned that if he clipped his device onto a 3-voltage device, the test
device would go poof.
if it's external to the application, it doesn't matter, since the test device
provides the supplies. I have a few of those old HP IC test clips, and the ones
I have are all malfunctioning in some way due to abuse prior to their falling
into my possession. That's actually why I have them.
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Thursday, November 22, 2001 12:56 PM
Subject: Re: 1771 floppy controller questions
>
> You'll want to be careful with the early DRAMs, as they used 3 supply rails,
and
> your tester of 5-volt-only DRAMs may die from
application to a 3-supply
DRAM.
It's unlikely that an 3-rail DRAM chip will damage the tester (it's not
going to magically apply overvoltage to the tester's inputs if it's only
fed with a 5V supply). But it's not going to work, and in some cases it
might damage the DRAM (some of the older DRAMs would fail if the -ve bias
supply was missing IIRC).
64K bit chips and above are +5V only in my experience. 4K bit and below
are almost always multiple supply rail types, and some of them had logic
inputs (clock/select) that needed higher-than-TTL levels. 16K bit are
normally 3 rail (4116 and equivalents), but +5V only ones exist (4816 IIRC).
-tony
3:07 p.m.
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4:47 p.m.
HP made a series of device testers that live on a test clip that you plug on
in-situ, and if it's designed for one set of supplies, and you hook up another,
you may not be pleased with the results. I've got a few of those out-of-circuit
testers, but the one I thing he (Tothwolf) is using is one of the type I'm
referring to. It would be a shame to damage one, as it can test a soldered-in
part without first unsoldering it.
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Thursday, November 22, 2001 7:07 PM
Subject: Re: 1771 floppy controller questions
>
> I was concerned that if he clipped his device onto a 3-voltage device, the
test
device would
go poof.
Most (all?) DRAM testers that I've seen test just the chips/simms out of
the circuit. It makes sense, since that way they can drive the address
lines, RAS/, CAS/, etc and veryify that the RAM works correctly on all
locations, etc.
-tony
10:21 p.m.
On Thu, 22 Nov 2001, Richard Erlacher wrote:
From: "Tony Duell"
<ard(a)p850ug1.demon.co.uk>
The tester set I have is designed for out of circuit use. Both units are
labeled 'ramcheck' and list the manufacturer as Innoventions, Inc.
Houston, TX. The tester supports 64k and 256k according to the label. I
opened up the tester, and found it contains an AMD 8088, a 27C32 eprom,
and a single dram chip, along with a mix of 74LS ttl logic chips. From the
looks of it, I could modify it to support 1024s and likely support older
chips if I design some sort of interface board. The speed checker unit is
designed to be used in-line with the tester (or maybe in circuit?), as it
has a ribbon cable with dip idc header on one end. It has a knob for
voltage selection labeled; Off, 4.5V, 5V, 5.5V, NR. I'm not sure what the
NR stands for, maybe no regulation? The other control is a 16 position
rotary switch (0-15), which is used x10 for speed selection in ns. Its
logic board contains a 7805 regulator, a handful of 74LS ttl, and a few
other chips I'd need to look up in a databook (Possibly a PROM and some
clock generators?)
-Toth
Most (all?) DRAM testers that I've seen test
just the chips/simms out of
the circuit. It makes sense, since that way they can drive the address
lines, RAS/, CAS/, etc and veryify that the RAM works correctly on all
locations, etc.
HP made a series of device testers that live on a test clip that you
plug on in-situ, and if it's designed for one set of supplies, and you
hook up another, you may not be pleased with the results. I've got a
few of those out-of-circuit testers, but the one I thing he (Tothwolf)
is using is one of the type I'm referring to. It would be a shame to
damage one, as it can test a soldered-in part without first
unsoldering it.
23 Nov
23 Nov
4:27 a.m.
Well, it sounds like it's less likely that you'll break the parts in your
tester, but it seems unlikely you'll be able to test the 4116's in it.
I got the mistaken impression that you had the HP test-clip type of IC tester,
of which I have a few, which require a functional component against which to
compare the function of the circuit under test. I've never figured out how
these work, since most of the ones I have are already brokent. One of these days
...
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, November 23, 2001 2:21 AM
Subject: Re: 1771 floppy controller questions
On Thu, 22 Nov 2001, Richard Erlacher wrote:
From: "Tony Duell"
<ard(a)p850ug1.demon.co.uk>
The tester set I have is designed for out of circuit use. Both units are
labeled 'ramcheck' and list the manufacturer as Innoventions, Inc.
Houston, TX. The tester supports 64k and 256k according to the label. I
opened up the tester, and found it contains an AMD 8088, a 27C32 eprom,
and a single dram chip, along with a mix of 74LS ttl logic chips. From the
looks of it, I could modify it to support 1024s and likely support older
chips if I design some sort of interface board. The speed checker unit is
designed to be used in-line with the tester (or maybe in circuit?), as it
has a ribbon cable with dip idc header on one end. It has a knob for
voltage selection labeled; Off, 4.5V, 5V, 5.5V, NR. I'm not sure what the
NR stands for, maybe no regulation? The other control is a 16 position
rotary switch (0-15), which is used x10 for speed selection in ns. Its
logic board contains a 7805 regulator, a handful of 74LS ttl, and a few
other chips I'd need to look up in a databook (Possibly a PROM and some
clock generators?)
-Toth
Most (all?) DRAM testers that I've seen test
just the chips/simms out of
the circuit. It makes sense, since that way they can drive the address
lines, RAS/, CAS/, etc and veryify that the RAM works correctly on all
locations, etc.
HP made a series of device testers that live on a test clip that you
plug on in-situ, and if it's designed for one set of supplies, and you
hook up another, you may not be pleased with the results. I've got a
few of those out-of-circuit testers, but the one I thing he (Tothwolf)
is using is one of the type I'm referring to. It would be a shame to
damage one, as it can test a soldered-in part without first
unsoldering it.
10:48 a.m.
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21 Nov
21 Nov
1:05 p.m.
On Wed, 21 Nov 2001, Tony Duell wrote:
It's more a matter of room than time right now, as my old "shop" is packed
floor to ceiling with computers, parts, and so on. My benches are also
currently covered up with even more parts and boxes.
I seem to remember one of these machines had a chip in one of the ram
banks that was missing a pin. It looked like it had corroded off. It was a
ceramic package with gold plated leads.
The ribbon in both computers was in somewhat bad shape. I was planning to
replace it with either a similar cable, or an IDC cable, as you suggested.
My model 1's keyboard cable had the same problem, and I replaced it with a
short bit of ribbon cable soldered directly to the boards. I'm planning to
replace that again with something better the next time I work on it.
I really don't remember if I got that far with the model 4. I may not have
even checked the 2 switching supplies, since at the time I bought it, I
didn't have any free time to spend on troubleshooting.
I think I saw some sort of temperature alarm/sensor plugged into the
output of one of the supplies in one of these machines. Was that a 3rd
party add-on or something that came standard?
-Toth
It has been a
number of years since I powered them up. Right now I think
they are both sitting disassembled in a couple of large boxes. I'm in the
When yopu have time to get them out again, let us know (or let me know),
and we can discuss troubleshooting them. process of
construction of a building just for my old hardware, so once
that is done, I'll pull both of them out and bench them and see what their
problems were. I think the model 3 would start up, but just plain lock up
about the time it was going to boot. I think it may be a ram problem. The
Mybe RAM. Most disk problems on the M3 and M4 are either the 1793 chip
(I've had to replace a couple) or more likely that infernal ribbon cable
between the CPU board and the disk controller. If you don't care about
your machine being unoriginal, you can use 40 way IDC cable and
connectors to replace it (just use 1 row of pins in the connector to
replace the 20 pin SIL socket on the CPU board or disk controller).
You're only using 20 wires in the cable, which is something of a waste,
but it's the easiest fix I've found [1]. model 4
didn't power up at all if I remember correctly.
In which case check the outputs of the power supplies -- both of them --
before doing anything else.
1:17 p.m.
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22 Nov
22 Nov
12:12 a.m.
On Thu, 22 Nov 2001, Tony Duell wrote:
Guess it comes with collecting eh?
At the time I thought the particular lead might have not been used, and or
someone damaged it when installing the chip. I had never seen a chip with
its lead corroded off like that. There's no visible water/moisture damage
on the rest of the board either, which seemed very odd.
Have you thought of trying a similar cable made from the newer plastics?
Teflon seems to be very very tough compared to whatever kind of plastic
they used in those older cables. What kind of current goes thru these
cables? Would it be possible to use one of the more flexible carbon types
instead of tin plated copper?
That's exactly the problem mine suffered from.
Well, if this is the machine that would not even turn on, that could
explain something...I know the factory seals had already been broken. I
wish I could get to these machines right now, I sure want to have another
look and fix em :P
-Toth
It's more
a matter of room than time right now, as my old "shop" is packed
floor to ceiling with computers, parts, and so on. My benches are also
currently covered up with even more parts and boxes.
I know exactly what you mean.... :-) I seem to
remember one of these machines had a chip in one of the ram
banks that was missing a pin. It looked like it had corroded off. It was a
ceramic package with gold plated leads.
Ah, if you have a visible problem like that, then you'd better fix it
;-). The machine is unlikely to work if a chip is missing a pin. Once
you've fixed that, you can start the real troubleshooting... replace it
with either a similar cable, or an IDC cable, as you suggested.
I've not found a source of the original type of cable. And I don't like
it much anyway (it seems to have reliability problems, which get a lot
worse if the cable is inserted and removed a few times). What I normally do is unsolder the connector from the
PCB. Replace it
with an SIL header (maybe just a row of pins, maybe one of the 'box
headers used with the IDC sockets with one row of pins removed). Then use
IDC cable/sockets to link the headers. Make sure you use the same row of
holes in both sockets, of course. I've done this in several machines and
not had any problems.
Could also use an SIL amp/berg connector and crimp pins to ribbon cable.
Might look a little more original, but it would take allot more work to
assemble then pressing on an IDC connector.
My model
1's keyboard cable had the same problem, and I replaced it with a
short bit of ribbon cable soldered directly to the boards. I'm planning to
replace that again with something better the next time I work on it.
The origianl M1 keyboard cables was a solid-core ribbon cable soldered to
both PCBs. It breaks if you unfold/reassemble the boards a few times. A
piece of normal ribbon cable seems to be a suitable replacement. I think I saw
some sort of temperature alarm/sensor plugged into the
output of one of the supplies in one of these machines. Was that a 3rd
party add-on or something that came standard?
If that's what it is, it's certainly not standard.
But disk-based M4s have a sound board. A small PCB with a 74LS74 chip, a
transistor and a beeper-thing on it. It has 4 wires coming off it, ending
in a 4 pin 0.1" Molex socket. It looks as though it could plug into a PSU
output connector, but it doesn't (doing so will kill the '74 at least).
It connects to a 4 pin plug on the CPU board just above the keyboard
connector. If yours was plugged into the PSU when you got the machine
then the previous owner was terminally clueless, and expect all sorts of
other problems!
9:27 a.m.
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11:32 a.m.
On Thu, 22 Nov 2001, Tony Duell wrote:
Guess it comes with collecting eh?
Especially if you collect minicomputers :-)
Even more if you collect mainframes, like me. 8-)
Peace... Sridhar
It's more
a matter of room than time right now, as my old "shop" is packed
floor to ceiling with computers, parts, and so on. My benches are also
currently covered up with even more parts and boxes.
I know exactly what you mean.... :-)
10:28 p.m.
On Thu, 22 Nov 2001, One Without Reason wrote:
On Thu, 22 Nov 2001, Tony Duell wrote:
Especially if you collect minicomputers :-)
Even more if you collect mainframes, like me. 8-)
Well, my favorite stuff to collect is old SGI and Sun gear. It can take up
quite a bit of room in a hurry, especially if you have monitors for them.
-Toth
> It's more a matter of room than time right
now, as my old "shop" is packed
> floor to ceiling with computers, parts, and so on. My benches are also
> currently covered up with even more parts and boxes.
I know exactly what you mean.... :-)
Guess it comes with collecting eh?
10:55 p.m.
On Thu, 22 Nov 2001, Tony Duell wrote:
I wonder if it would be worth soldering a new pin to what's left of that
chip's lead? It looked like it had just corroded off, but with no other
signs of moisture, I was kinda puzzled.
Sounds like I may have to experiment a little once I get some clear bench
space ;)
I can often find them in large sizes, and use an a sharp X-acto to trim
them to whatever pin count I need. [If anyone decides to try this, be very
very careful, those blades are extremely sharp, and will cut thru the
connector slow at first, then slice thru the remaining material very
fast.] The leftovers can be recycled for even shorter connectors. This
would not be economical for more then a few dozen connectors however.
I think that machine is the model 4, which I think came from a surplus
dealer. There is no way of knowing what all someone tried to do to this
thing before I bought it. The model 3 came from a thrift shop, and seemed
to be in much better overall shape, and may have still had its factory
seals intact.
-Toth
At the time I
thought the particular lead might have not been used, and or
someone damaged it when installing the chip. I had never seen a chip with
IIRC, the DRAMs in the model 3 are 16K * 1 4116s or similar. All the pins
are used on these chips. If a pin is missing, then you are going to have
problems... Teflon seems
to be very very tough compared to whatever kind of plastic
they used in those older cables. What kind of current goes thru these
cables? Would it be possible to use one of the more flexible carbon types
instead of tin plated copper?
In the Model 3/4 it's just logic level signals. There's a separate power
connector on the disk controller board. But I suspect that carbon-cable
would have too high a resistance to be reliable (if nothing else it's
going to delay the signals somewhat due to the RC time constant of the
cable and the input capacitance of the chips on the board). Probably not
a good idea. Could also use
an SIL amp/berg connector and crimp pins to ribbon cable.
Might look a little more original, but it would take allot more work to
assemble then pressing on an IDC connector.
It's a lot slower to assemble, and it's actually slightly taller. Also,
those SIL Berg/Amp/Molex connectors are difficult to find in >10 way
sizes (yes, they're made, but nobody seems to stock them). I prefer to
use parts I can get in 1-off quantities :-) Well, if this
is the machine that would not even turn on, that could
explain something...I know the factory seals had already been broken. I
Argh!. If the sound board has been plugged into the PSU output there's no
way of knowing what else has been misconnected and what damage has been
done. That's one reason to give a machine a complete visual inspection
before applying power, hoping that if things are totally misconnected
that the previous owner didn't power the machine up like that (some hope,
I know).
23 Nov
23 Nov
4:29 a.m.
If you need 4116's, just send me your address. I've got more than I'll EVER
use, believe me.
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, November 23, 2001 2:55 AM
Subject: Re: 1771 floppy controller questions
On Thu, 22 Nov 2001, Tony Duell wrote:
I wonder if it would be worth soldering a new pin to what's left of that
chip's lead? It looked like it had just corroded off, but with no other
signs of moisture, I was kinda puzzled.
Sounds like I may have to experiment a little once I get some clear bench
space ;)
I can often find them in large sizes, and use an a sharp X-acto to trim
them to whatever pin count I need. [If anyone decides to try this, be very
very careful, those blades are extremely sharp, and will cut thru the
connector slow at first, then slice thru the remaining material very
fast.] The leftovers can be recycled for even shorter connectors. This
would not be economical for more then a few dozen connectors however.
I think that machine is the model 4, which I think came from a surplus
dealer. There is no way of knowing what all someone tried to do to this
thing before I bought it. The model 3 came from a thrift shop, and seemed
to be in much better overall shape, and may have still had its factory
seals intact.
-Toth
At the
time I thought the particular lead might have not been used, and or
someone damaged it when installing the chip. I had never seen a chip with
IIRC, the DRAMs in the model 3 are 16K * 1 4116s or similar. All the pins
are used on these chips. If a pin is missing, then you are going to have
problems... Teflon
seems to be very very tough compared to whatever kind of plastic
they used in those older cables. What kind of current goes thru these
cables? Would it be possible to use one of the more flexible carbon types
instead of tin plated copper?
In the Model 3/4 it's just logic level signals. There's a separate power
connector on the disk controller board. But I suspect that carbon-cable
would have too high a resistance to be reliable (if nothing else it's
going to delay the signals somewhat due to the RC time constant of the
cable and the input capacitance of the chips on the board). Probably not
a good idea. Could
also use an SIL amp/berg connector and crimp pins to ribbon cable.
Might look a little more original, but it would take allot more work to
assemble then pressing on an IDC connector.
It's a lot slower to assemble, and it's actually slightly taller. Also,
those SIL Berg/Amp/Molex connectors are difficult to find in >10 way
sizes (yes, they're made, but nobody seems to stock them). I prefer to
use parts I can get in 1-off quantities :-) Well, if
this is the machine that would not even turn on, that could
explain something...I know the factory seals had already been broken. I
Argh!. If the sound board has been plugged into the PSU output there's no
way of knowing what else has been misconnected and what damage has been
done. That's one reason to give a machine a complete visual inspection
before applying power, hoping that if things are totally misconnected
that the previous owner didn't power the machine up like that (some hope,
I know).
26 Nov
26 Nov
3:46 p.m.
On Fri, 23 Nov 2001, Richard Erlacher wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
Thanks for the offer, I'll try my luck at repairing this one before I
replace it. I think some of the chips in that machine were replaced
already. It has a few dip style chips mixed in with the standard ceramic
ones.
-Toth
I wonder if it would be worth soldering a new pin
to what's left of that
chip's lead? It looked like it had just corroded off, but with no other
signs of moisture, I was kinda puzzled.
If you need 4116's, just send me your address. I've got more than I'll EVER
use, believe me.
23 Nov
23 Nov
11:01 a.m.
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26 Nov
26 Nov
3:42 p.m.
On Fri, 23 Nov 2001, Tony Duell wrote:
I done this a few times. The last chip I repaired this way, I used a
dental bur bit in a dremel to remove enough of the plastic to solder on a
new lead. Whatever it is they make those plastic dips out of sure is
tough...
I will post the info to the list when I get it out to start work on it.
-Toth
I wonder if it
would be worth soldering a new pin to what's left of that
chip's lead? It looked like it had just corroded off, but with no other
It's worth a try. I've soldered pins onto irreplaceable custom
chips/ROMs/etc and got them to work again. signs of
moisture, I was kinda puzzled.
It supprises me, too... I'd be interested to know which pin it is. 
23 Nov
23 Nov
1:02 p.m.
On Fri, 23 Nov 2001, Tothwolf wrote:
On Thu, 22 Nov 2001, Tony Duell wrote:
I wonder if it would be worth soldering a new pin to what's left of that
chip's lead? It looked like it had just corroded off, but with no other
signs of moisture, I was kinda puzzled.
Why not? You might want to checkout the socket pretty thoroughly,
though.
- don
At the
time I thought the particular lead might have not been used, and or
someone damaged it when installing the chip. I had never seen a chip with
IIRC, the DRAMs in the model 3 are 16K * 1 4116s or similar. All the pins
are used on these chips. If a pin is missing, then you are going to have
problems...
26 Nov
26 Nov
3:38 p.m.
On Fri, 23 Nov 2001, Don Maslin wrote:
On Fri, 23 Nov 2001, Tothwolf wrote:
I didn't see any damage when I originally looked at it, but I will double
check it before I plug in a repaired/replacement chip.
-Toth
On Thu, 22 Nov 2001, Tony Duell wrote:
I wonder if it would be worth soldering a new pin to what's left of that
chip's lead? It looked like it had just corroded off, but with no other
signs of moisture, I was kinda puzzled.
Why not? You might want to checkout the socket pretty thoroughly,
though. At the
time I thought the particular lead might have not been used, and or
someone damaged it when installing the chip. I had never seen a chip with
IIRC, the DRAMs in the model 3 are 16K * 1 4116s or similar. All the pins
are used on these chips. If a pin is missing, then you are going to have
problems... 
27 Nov
27 Nov
6:07 a.m.
On Mon, 26 Nov 2001, Tothwolf wrote:
> > > > someone damaged it when installing
the chip. I had never seen a chip with
A likely possibility. I have seen occasional
cases where a chip will work
with a pin bent under making intermittent contact, including one OEM IBM
MDA card!
> > I wonder if it would be worth soldering a
new pin to what's left of that
> > chip's lead? It looked like it had just corroded off, but with no other
> > signs of moisture, I was kinda puzzled.
It is rather unlikely that it would have corroded off, particularly with a
gold or gold plated pin. More likely that it was broken during
installation, and possibly continued to work for a while with the two
broken ends pushing against each other.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
7:07 a.m.
On Tue, 27 Nov 2001, Fred Cisin (XenoSoft) wrote:
It could be that it was bent under, still in contact with the socket's
contact, and due to moisture/thermal stresses, the weakened metal
eventually broke. The other half of the lead wasn't in the socket, so this
seems to be a likely scenario.
-Toth
On Mon, 26 Nov 2001, Tothwolf wrote:
I've seen this more than a few times myself, even on modern computer
boards...
> > > > someone damaged it when
installing the chip. I had never seen a chip with
A likely possibility. I have seen occasional cases where a chip will
work with a pin bent under making intermittent contact, including one
OEM IBM MDA card! > > I
wonder if it would be worth soldering a new pin to what's left of that
> > chip's lead? It looked like it had just corroded off, but with no other
> > signs of moisture, I was kinda puzzled.
It is rather unlikely that it would have corroded off, particularly
with a gold or gold plated pin. More likely that it was broken during
installation, and possibly continued to work for a while with the two
broken ends pushing against each other.
21 Nov
21 Nov
1:48 p.m.
Back in the very late '70's a product similar to flex PCB material was
introduced as a replacement for a ribbon cable, that fit in a 20-pin SIP socket,
in this case, yet weren't custom circuits. I've got some of that stuff around,
as a sample pack I got back then yet haven't used. Unfortunately, when I opened
them to examine 'em, I didn't save the label, so I can't give you a product
name. I thought of this bacause ribbon cable soldered to PCB's always seemed to
me to be a source of trouble. I had keyboards connected with soldered ribbon
for some time and it seems to me that I was frequently restripping and
resoldering, while those attached with connectors occasionally required that I
check that the connectors were securely plugged, but nothing else.
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Wednesday, November 21, 2001 5:05 PM
Subject: Re: 1771 floppy controller questions
On Wed, 21 Nov 2001, Tony Duell wrote:
It's more a matter of room than time right now, as my old "shop" is packed
floor to ceiling with computers, parts, and so on. My benches are also
currently covered up with even more parts and boxes.
I seem to remember one of these machines had a chip in one of the ram
banks that was missing a pin. It looked like it had corroded off. It was a
ceramic package with gold plated leads.
The ribbon in both computers was in somewhat bad shape. I was planning to
replace it with either a similar cable, or an IDC cable, as you suggested.
My model 1's keyboard cable had the same problem, and I replaced it with a
short bit of ribbon cable soldered directly to the boards. I'm planning to
replace that again with something better the next time I work on it.
I really don't remember if I got that far with the model 4. I may not have
even checked the 2 switching supplies, since at the time I bought it, I
didn't have any free time to spend on troubleshooting.
I think I saw some sort of temperature alarm/sensor plugged into the
output of one of the supplies in one of these machines. Was that a 3rd
party add-on or something that came standard?
-Toth
It has
been a number of years since I powered them up. Right now I think
they are both sitting disassembled in a couple of large boxes. I'm in the
When yopu have time to get them out again, let us know (or let me know),
and we can discuss troubleshooting them. process
of construction of a building just for my old hardware, so once
that is done, I'll pull both of them out and bench them and see what their
problems were. I think the model 3 would start up, but just plain lock up
about the time it was going to boot. I think it may be a ram problem. The
Mybe RAM. Most disk problems on the M3 and M4 are either the 1793 chip
(I've had to replace a couple) or more likely that infernal ribbon cable
between the CPU board and the disk controller. If you don't care about
your machine being unoriginal, you can use 40 way IDC cable and
connectors to replace it (just use 1 row of pins in the connector to
replace the 20 pin SIL socket on the CPU board or disk controller).
You're only using 20 wires in the cable, which is something of a waste,
but it's the easiest fix I've found [1]. model 4
didn't power up at all if I remember correctly.
In which case check the outputs of the power supplies -- both of them --
before doing anything else.
22 Nov
22 Nov
12:18 a.m.
On Wed, 21 Nov 2001, Richard Erlacher wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
<snip>
The ribbon in both computers was in somewhat bad shape. I was planning to
replace it with either a similar cable, or an IDC cable, as you suggested.
My model 1's keyboard cable had the same problem, and I replaced it with a
short bit of ribbon cable soldered directly to the boards. I'm planning to
replace that again with something better the next time I work on it.
I thought of this bacause ribbon cable soldered to
PCB's always seemed
to me to be a source of trouble. I had keyboards connected with
soldered ribbon for some time and it seems to me that I was frequently
restripping and resoldering, while those attached with connectors
occasionally required that I check that the connectors were securely
plugged, but nothing else.
This is the exact problem I want to avoid with my model 1. I've considered
using crimp on pins on each wire of the ribbon cable, since they would
provide some strain relief for the individual wires.
-Toth
9 a.m.
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20 Nov
20 Nov
1:15 p.m.
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26 Nov
26 Nov
10:21 a.m.
--- Richard Erlacher <edick(a)idcomm.com> wrote:
You can get one for cheap if you go down to the thrift
store and buy an
old TRS-80. That will cost less than a new WD1771, I'd bet.
I'll _trade_ you an old TRS-80 for a WD1771. I haven't seen
non-Commodore/Apple/IBM-compatible computers* at the thrift stores
in a long, long time. I suspect they don't bother setting them out
and just trash them.
-ethan
* - Not even Atari or Coleco or any of the once-common home machines.
__________________________________________________
Do You Yahoo!?
Yahoo! GeoCities - quick and easy web site hosting, just $8.95/month.
http://geocities.yahoo.com/ps/info1
11:49 a.m.
Actually, my initial comment was that I'd happily junk a Coco in order to get a
WD1773. I've got plenty of 1771's, and a few 179x's in my parts stock. If I
needed a 1771, unlikely, but if it happened, I'd simply unplug one from an old
"Big Board" SBC. I've got an upgrade to a 179x for them anyway. It's
been a
while since I last saw a Coco, and now that I know there's a 1773 in them, I'll
snag one first chance I get. I've still got TRS-80 doc's lying about from back
in the late '70's, but I've never owned a TRS-80.
Dick
----- Original Message -----
From: "Ethan Dicks" <erd_6502(a)yahoo.com>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, November 26, 2001 2:21 PM
Subject: Re: 1771 floppy controller questions
--- Richard Erlacher <edick(a)idcomm.com> wrote:
You can get one for cheap if you go down to the
thrift store and buy an
old TRS-80. That will cost less than a new WD1771, I'd bet.
I'll _trade_ you an old TRS-80 for a WD1771. I haven't seen
non-Commodore/Apple/IBM-compatible computers* at the thrift stores
in a long, long time. I suspect they don't bother setting them out
and just trash them.
-ethan
* - Not even Atari or Coleco or any of the once-common home machines.
__________________________________________________
Do You Yahoo!?
Yahoo! GeoCities - quick and easy web site hosting, just $8.95/month.
http://geocities.yahoo.com/ps/info1
3:36 p.m.
On Mon, 26 Nov 2001, Richard Erlacher wrote:
From: "Ethan Dicks"
<erd_6502(a)yahoo.com>
Well, I now have a pair of brand new WD1771 chips on hand, one for my
model 1, and one spare. A local vendor I use will sell me as many chips as
I need for $5ea. They have both the WD and National versions of the chip.
I imagine they have another 25-40+ chips left in stock, tho a good many of
them need to have their pins straightened.
-Toth
--- Richard Erlacher <edick(a)idcomm.com>
wrote:
Actually, my initial comment was that I'd happily junk a Coco in order
to get a WD1773. I've got plenty of 1771's, and a few 179x's in my
parts stock. If I needed a 1771, unlikely, but if it happened, I'd
simply unplug one from an old "Big Board" SBC. I've got an upgrade to
a 179x for them anyway. It's been a while since I last saw a Coco,
and now that I know there's a 1773 in them, I'll snag one first chance
I get. I've still got TRS-80 doc's lying about from back in the late
'70's, but I've never owned a TRS-80. You can get one for cheap if you go down to the
thrift store and buy an
old TRS-80. That will cost less than a new WD1771, I'd bet.
I'll _trade_ you an old TRS-80 for a WD1771. I haven't seen
non-Commodore/Apple/IBM-compatible computers* at the thrift stores
in a long, long time. I suspect they don't bother setting them out
and just trash them.
27 Nov
27 Nov
4:17 a.m.
Our local Gateway Electronics store has these in stock, but they actually think
they're worth more than the 179x types. Neither is under $10. Fortunately,
there's no associated stock issue for me.
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, November 26, 2001 7:36 PM
Subject: Re: 1771 floppy controller questions
On Mon, 26 Nov 2001, Richard Erlacher wrote:
From: "Ethan Dicks"
<erd_6502(a)yahoo.com>
Well, I now have a pair of brand new WD1771 chips on hand, one for my
model 1, and one spare. A local vendor I use will sell me as many chips as
I need for $5ea. They have both the WD and National versions of the chip.
I imagine they have another 25-40+ chips left in stock, tho a good many of
them need to have their pins straightened.
-Toth
--- Richard Erlacher <edick(a)idcomm.com>
wrote:
Actually, my initial comment was that I'd happily junk a Coco in order
to get a WD1773. I've got plenty of 1771's, and a few 179x's in my
parts stock. If I needed a 1771, unlikely, but if it happened, I'd
simply unplug one from an old "Big Board" SBC. I've got an upgrade to
a 179x for them anyway. It's been a while since I last saw a Coco,
and now that I know there's a 1773 in them, I'll snag one first chance
I get. I've still got TRS-80 doc's lying about from back in the late
'70's, but I've never owned a TRS-80. You can get one for cheap if you go down to the
thrift store and buy an
old TRS-80. That will cost less than a new WD1771, I'd bet.
I'll _trade_ you an old TRS-80 for a WD1771. I haven't seen
non-Commodore/Apple/IBM-compatible computers* at the thrift stores
in a long, long time. I suspect they don't bother setting them out
and just trash them.
7 a.m.
On Tue, 27 Nov 2001, Richard Erlacher wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
Maybe that's where my vendor originally got their price from? They
actually thought the 1771 was worth more then $20ea...Thanks to the tip
about B.G. Micro selling the chip for $5, my vendor decided to match the
price.
-Toth
Well, I now have a pair of brand new WD1771 chips
on hand, one for my
model 1, and one spare. A local vendor I use will sell me as many chips as
I need for $5ea. They have both the WD and National versions of the chip.
I imagine they have another 25-40+ chips left in stock, tho a good many of
them need to have their pins straightened.
Our local Gateway Electronics store has these in stock, but they
actually think they're worth more than the 179x types. Neither is
under $10. Fortunately, there's no associated stock issue for me. 
19 Nov
19 Nov
4:22 p.m.
B. G. Micro, www.bgmicro.com, has FD1771s for $4.95.
Michael Holley
http://www.swtpc.com/mholley/index.html
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, November 19, 2001 12:11 PM
Subject: 1771 floppy controller questions
I have a complete TRS-80 Model I that has a dead
Western Digital FD1771-01
chip in its expansion interface. Does anyone know if a National 1771-B01
is a suitable replacement? What would be a fair/reasonable price for a new
1771 these days?
-Toth
7:51 p.m.
On Mon, 19 Nov 2001, Michael Holley wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
Thanks for the info. I should be able to get my local vendor to match that
price since B.G. Micro is a fairly well known vendor.
-Toth
I have a complete TRS-80 Model I that has a dead
Western Digital FD1771-01
chip in its expansion interface. Does anyone know if a National 1771-B01
is a suitable replacement? What would be a fair/reasonable price for a new
1771 these days?
B. G. Micro, www.bgmicro.com, has FD1771s for $4.95.
9:42 p.m.
What is it that makes you believe that the 1771 s the problem?
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, November 19, 2001 11:51 PM
Subject: Re: 1771 floppy controller questions
On Mon, 19 Nov 2001, Michael Holley wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
Thanks for the info. I should be able to get my local vendor to match that
price since B.G. Micro is a fairly well known vendor.
-Toth
I have a complete TRS-80 Model I that has a dead
Western Digital FD1771-01
chip in its expansion interface. Does anyone know if a National 1771-B01
is a suitable replacement? What would be a fair/reasonable price for a new
1771 these days?
B. G. Micro, www.bgmicro.com, has FD1771s for $4.95.
10:25 p.m.
On Tue, 20 Nov 2001, Richard Erlacher wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
Well, I accidentally plugged the chip in backward when troubleshooting the
floppy interface right after I got it. It turned out that the floppy
ribbon was bad, just due to age I guess. I don't think the chip let out
its magic smoke, but it certainly does not work now ;)
-Toth
On Mon, 19 Nov 2001, Michael Holley wrote:
What is it that makes you believe that the 1771 s the problem? From: "Tothwolf"
<tothwolf(a)concentric.net>
Thanks for the info. I should be able to get my local vendor to match that
price since B.G. Micro is a fairly well known vendor. I have a complete TRS-80 Model I that has a dead
Western Digital FD1771-01
chip in its expansion interface. Does anyone know if a National 1771-B01
is a suitable replacement? What would be a fair/reasonable price for a new
1771 these days?
B. G. Micro, www.bgmicro.com, has FD1771s for $4.95.
20 Nov
20 Nov
4:10 a.m.
OK ... I can believe you'd reach that conclusion from what you describe. I've
done that on one of those "late nights" on more than one occasion. It's
reasonable to assume the part is toast, given that there are several supplies,
each of which has been applied to the wrong pins. Too bad ...
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Tuesday, November 20, 2001 2:25 AM
Subject: Re: 1771 floppy controller questions
What is it that makes you believe that the 1771 s the problem?
Well, I accidentally plugged the chip in backward when troubleshooting the
floppy interface right after I got it. It turned out that the floppy
ribbon was bad, just due to age I guess. I don't think the chip let out
its magic smoke, but it certainly does not work now ;)
-Toth
On Tue, 20 Nov 2001, Richard Erlacher wrote:
> From: "Tothwolf" <tothwolf(a)concentric.net>
> > On Mon, 19 Nov 2001, Michael Holley wrote:
> > > From: "Tothwolf" <tothwolf(a)concentric.net>
> > >
> > > > I have a complete TRS-80 Model I that has a dead Western Digital
FD1771-01
> > > > chip in its expansion interface.
Does anyone know if a National
1771-B01
> > > > is a suitable replacement? What
would be a fair/reasonable price for a
new
> 1771
these days?
B. G. Micro, www.bgmicro.com, has FD1771s for $4.95.
Thanks for the info. I should be able to get my local vendor to match that
price since B.G. Micro is a fairly well known vendor.
4:51 a.m.
On Tue, 20 Nov 2001, Richard Erlacher wrote:
From: "Tothwolf"
<tothwolf(a)concentric.net>
I'm really not too worried about it, since the 1771 does seem to be
available and I have the technical reference book for the expansion
interface. I don't think there are any unusual or proprietary chips used
in the expansion interface with the exception of the floppy controller. If
it took out any other logic chips with it, I should be able to replace
those easily.
It appears that my local vendor may have just assumed the part he has in
stock is a National, since I can't find any references to National ever
manufacturing a 1771, and the -B01 is a WD suffix.
-Toth
On Tue, 20 Nov 2001, Richard Erlacher wrote:
OK ... I can believe you'd reach that conclusion from what you describe. I've
done that on one of those "late nights" on more than one occasion. It's
reasonable to assume the part is toast, given that there are several supplies,
each of which has been applied to the wrong pins. Too bad ... What is it that makes you believe that the 1771 s
the problem?
Well, I accidentally plugged the chip in backward when troubleshooting the
floppy interface right after I got it. It turned out that the floppy
ribbon was bad, just due to age I guess. I don't think the chip let out
its magic smoke, but it certainly does not work now ;)
5:36 a.m.
I don't know right offhand of any second sources, except for Intel, which did,
IIRC, make a 1771-equivalent/compatible for a time. They went the NEC route
when MFM became popular, however.
WD also made a 1781 which was M2FM capable, and, as some folks will tell you,
THAT's a hard modulation scheme to support.
As I mentioned before, it might be worthwhile to communicate with Tony Duell
regarding the expansion interface, as he recently admitted he'd actually made
the model-1 disk interface work as it was designed to work. A lot of folks
couldn't get reasonable reliability until they bought a third-party enhancment
for the floppy interface.
Dick
----- Original Message -----
From: "Tothwolf" <tothwolf(a)concentric.net>
To: <classiccmp(a)classiccmp.org>
Sent: Tuesday, November 20, 2001 8:51 AM
Subject: Re: 1771 floppy controller questions
On Tue, 20 Nov 2001, Richard Erlacher wrote:
> From: "Tothwolf" <tothwolf(a)concentric.net>
> > On Tue, 20 Nov 2001, Richard Erlacher wrote:
> >
> > > What is it that makes you believe that the 1771 s the problem?
> >
> > Well, I accidentally plugged the chip in backward when troubleshooting the
> > floppy interface right after I got it. It turned out that the floppy
> > ribbon was bad, just due to age I guess. I don't think the chip let out
> > its magic smoke, but it certainly does not work now ;)
>
> OK ... I can believe you'd reach that conclusion from what you describe.
I've
> done that on one of those "late nights"
on more than one occasion. It's
> reasonable to assume the part is toast, given that there are several
supplies,
each of which
has been applied to the wrong pins. Too bad ...
I'm really not too worried about it, since the 1771 does seem to be
available and I have the technical reference book for the expansion
interface. I don't think there are any unusual or proprietary chips used
in the expansion interface with the exception of the floppy controller. If
it took out any other logic chips with it, I should be able to replace
those easily.
It appears that my local vendor may have just assumed the part he has in
stock is a National, since I can't find any references to National ever
manufacturing a 1771, and the -B01 is a WD suffix.
-Toth
1:47 p.m.
Richard Erlacher <edick(a)idcomm.com> wrote (concerning
plugging a 1771 in backwards):
I've done that on one of those "late
nights" on more than one
occasion.
I discovered a more creative way to destroy a 1771 once. It was on a
highly personalised system based on a Dick Smith Super 80 (not System
80!) for which I had built my own disk controller. A friend of mine
was attempting to build a colour graphics display, and I had the
prototype connected between my system and a TV (via RF).
There was a lot of herringbone stuff on the screen, and I wondered
whether hash from the computer was getting into the RF modulator
through the power supply, so I decided to try filtering it with an
inductor, to wit, one winding of an old audio output transformer that
I had lying about.
It didn't help, so I disconnected it. With the power on. The disk
drive head went clunk, and the motor turned on. And stayed
on. Permanently. At that point I realised that I had neglected to
anticipate the effects of inductive kickback.
I couldn't get a 1771 to replace it with at the time, so I got a 1791,
which looked like a better part anyway (capable of double density [1]) so
I wasn't unhappy about having to make a few changes to the circuitry,
such as devising an external data separator.
More of a challenge was when I discovered that, of the 4 kinds of data
mark supported by the 1771, the 1791 could only read two of them. And,
of course, the one I had chosen to use (in my unique home-brewed DOS)
was one of the ones no longer supported, so I couldn't read any of my
disks! Recovering from that situation was an interesting exercise...
Footnotes:
[1] I never made use of it, though, since my 2MHz Z80 couldn't
keep up with feeding the data buffer fast enough. :-(
Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury, | A citizen of NewZealandCorp, a |
Christchurch, New Zealand | wholly-owned subsidiary of USA Inc. |
greg(a)cosc.canterbury.ac.nz +--------------------------------------+
7 a.m.
New subject: 1771 chip brings $565 on EBAY?
Well, I accidentally plugged the chip in backward when
troubleshooting the
floppy interface right after I got it. It turned out that the floppy
ribbon was bad, just due to age I guess. I don't think the chip let out
its magic smoke, but it certainly does not work now ;)
A modest proposal:
Since the chip collectors don't REALLY care whether tha chip is actually
WORKING, ...
So long as the escape of the magic smoke didn't leave any marks, save the
electrically dead chips, and let the ship collectors have them.
If the chip collectors would be willing to trade working common varieties
of chips for dead rarer colors, ...
C'mon guys, got a working common variety 1771 for Toth?
Sellam: I checked through some of my junk, and couldn't find ANY dayglo
yellow 8080s. Would other dayglo colors work?
--
Grumpy Ol' Fred cisin(a)xenosoft.com
NOTE: My ISP is having some problems. If you have difficulty reaching me
at this e-mail address, you can leave a message at:
fcisin(a)merritt.edu
cisin(a)info.sims.berkeley.edu
9:01 a.m.
New subject: 1771 chip brings $565 on EBAY?
On Tue, 20 Nov 2001, Fred Cisin (XenoSoft) wrote:
Eh...my dead chip isn't in good shape, it got hot enough to almost totally
erase its markings. I think quite a few of the pins got broken off after I
tossed the dead chip in the junk box too. I just can't see someone wanting
a dead 1771 w/ faint markings and broken pins...I guess it would look ok
if it were glued to something and had some clear coat applied to the top
to make the writing show up again ;P
-Toth
Well, I
accidentally plugged the chip in backward when troubleshooting the
floppy interface right after I got it. It turned out that the floppy
ribbon was bad, just due to age I guess. I don't think the chip let out
its magic smoke, but it certainly does not work now ;)
A modest proposal:
Since the chip collectors don't REALLY care whether tha chip is actually
WORKING, ...
So long as the escape of the magic smoke didn't leave any marks, save the
electrically dead chips, and let the ship collectors have them.
If the chip collectors would be willing to trade working common varieties
of chips for dead rarer colors, ...
C'mon guys, got a working common variety 1771 for Toth? 
11:21 p.m.
New subject: 1771 chip brings $565 on EBAY?
> > Well, I accidentally plugged the chip in
backward when troubleshooting the
> > floppy interface right after I got it. It turned out that the floppy
> > ribbon was bad, just due to age I guess. I don't think the chip let out
> > its magic smoke, but it certainly does not work now ;)
> A modest proposal:
> Since the chip collectors don't REALLY care whether tha chip is actually
> WORKING, ...
> So long as the escape of the magic smoke didn't leave any marks, save the
> electrically dead chips, and let the ship collectors have them.
> If the chip collectors would be willing to trade
working common varieties
> of chips for dead rarer colors, ...
> C'mon guys, got a working common variety 1771 for Toth?
Eh...my dead chip isn't in good shape, it got hot
enough to almost totally
erase its markings. I think quite a few of the pins got broken off after I
tossed the dead chip in the junk box too. I just can't see someone wanting
a dead 1771 w/ faint markings and broken pins...I guess it would look ok
if it were glued to something and had some clear coat applied to the top
to make the writing show up again ;P
Remember, this is Antiqu Stuff business - it could be a good idea to
have a skilled artist restore the optical condition. If you invest,
lets say two or threehundres Dollars you still may get a prety good
deal.
SCNR
H.
--
VCF Europa 3.0 am 27./28. April 2002 in Muenchen
http://www.vcfe.org/
21 Nov
21 Nov
2:53 a.m.
New subject: 1771 chip brings $565 on EBAY?
On Wed, 21 Nov 2001, Hans Franke wrote:
Remember, this is Antiqu Stuff business - it could be
a good idea to
have a skilled artist restore the optical condition. If you invest,
lets say two or threehundres Dollars you still may get a prety good
deal.
Somehow I doubt that...I can get a NOS chip for $5, so it don't seem to be
worth it. I think I'll just toss the old one back into the junk box and
let it collect value with age. Who knows? maybe in 20 years it'll be worth
something ;P
-Toth
4:30 a.m.
New subject: 1771 chip brings $565 on EBAY?
Tothwolf wrote:
On Wed, 21 Nov 2001, Hans Franke wrote:
Sounds like tube audio here. A generic NOS abc tube $5. A new gold
plated fancy
abc tube from the fancy audio people $35. And of course the latest amp
needs
8 of them. :(
A middle road is needed here.
Remember, this is Antiqu Stuff business - it
could be a good idea to
have a skilled artist restore the optical condition. If you invest,
lets say two or threehundres Dollars you still may get a prety good
deal.
Somehow I doubt that...I can get a NOS chip for $5, so it don't seem to be
worth it. I think I'll just toss the old one back into the junk box and
let it collect value with age. Who knows? maybe in 20 years it'll be worth
something ;P -Toth
Ben Franchuk.
--
Live "Pre-historic Cpu's" -- and you thought they were extinct.
www.jetnet.ab.ca/users/bfranchuk/index.html
20 Nov
20 Nov
9:56 a.m.
New subject: 1771 chip brings $565 on EBAY?
"Fred Cisin (XenoSoft)" wrote:
Sellam: I checked through some of my junk, and
couldn't find ANY dayglo
yellow 8080s. Would other dayglo colors work?
How about the eerie green from a 8080 removed from Three Mile Island. :)
Ben Franchuk.
--
Live "Pre-historic Cpu's" -- and you thought they were extinct.
www.jetnet.ab.ca/users/bfranchuk/index.html
8273
days inactive
8281
days old
59 comments
12 participants
participants (12)
-
ard＠p850ug1.demon.co.uk -
bfranchuk＠jetnet.ab.ca -
cisin＠xenosoft.com -
donm＠cts.com -
edick＠idcomm.com -
erd_6502＠yahoo.com -
greg＠cosc.canterbury.ac.nz -
Hans.Franke＠mch20.sbs.de -
jpero＠sympatico.ca -
swtpc6800＠home.com -
tothwolf＠concentric.net -
vance＠ikickass.org