24 Nov
2003
24 Nov
'03
3:55 p.m.
Well, it finally happened :-). I was able to talk to my pdp-8L at 19200
baud over an RS-232 link from my PC. Just a cable swap and some dip-switch
adjustments and I can talk to my TTY over current loop.
However, my TTY doesn't have the reader-run mod. Does anyone have a TTY
with reader-run in or near the PDX metro area that I could test with?
Thanks,
Vince
25 Nov
25 Nov
9:49 a.m.
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11:22 a.m.
Is there a good reason for not fitting the reader run
modification
(basically a relay) to your ASR?
I could do that if I had one, and knew how :-). Repairing my TTY (needs
repairs) and adding reader-run are on my list of things to do, but no where
near as urgent (in my mind) as getting these cards tested.
One of the repairs needed on the TTY is to get the reader reliable enough to
load programs. Until then, reader-run isn't too important for it, except in
the context of testing the W076 replacement.
Is it that easy to mod the TTY? Where do you get the relay?
Vince
26 Nov
26 Nov
10:43 a.m.
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12:28 p.m.
> > Is there a good reason for not fitting the
reader run modification
> > (basically a relay) to your ASR?
>
> I could do that if I had one, and knew how :-). Repairing my TTY (needs
> repairs) and adding reader-run are on my list of things to do, but no
where
> near as urgent (in my mind) as getting these
cards tested.
>
> One of the repairs needed on the TTY is to get the reader reliable
enough to
> load programs. Until then, reader-run isn't
too important for it,
except in
I have _never_ really liked the ASR33's reader. It's slow, it's not kind
to tapes, and the contacts are not that reliable, even wben newly set up
as per the manual. If you're serious about paper tape, get a 'high speed
reader' The DEC PC04 or PC05 (which you need depends on the machine, the
latter can be turned into the former -- I've done it) aren't too bad, but
they're still sproket fed (and thus can tear tapes). The UK-made Trends
are really nice readers (a lot turned up surplus about 15 years ago, I
grabbed all I could find!).
I have a PC04. The point here is not to create an optimal tape reading
environment; it is to test whether the W076 replacement card is or isn't
generating this signal with sufficient drive to close the reader-run relay,
if one is present. (I actually intend to load most of my images over RS-232
from a PC.)
Is it that
easy to mod the TTY? Where do you get the relay?
The instructions for doing this are in at least one DEC printest, similar
instructions are in the Intel MCS8i manual, and doubtless elsewhere. No idea where you'd get the relay these days. I
wonder if you could
design a solid-state switching circuit that would work, with an
opto-isolator on the input
Maybe, if I had specs for the relay. If I had the specs, I might even be
able to tell if I have a prayer of delivering sufficient drive current,
though I'd still prefer to test on real hardware before having a bunch of
boards manufactured.
Vince
27 Nov
27 Nov
1:11 a.m.
e.
I found them. I'd still need relay part number 4915. There are also some
things called "thyractors" called for.
Some place in the pdp-8E/M docs there must be specs for the TTY and
reader control circuits. Take a look at the TTY I/O prints and see
what devices DEC used to drive the relay circuit.
Mike
No idea where you'd get the relay these days.
I wonder if you could
design a solid-state switching circuit that would work, with an
opto-isolator on the input
Maybe, if I had specs for the relay. If I had the specs, I might even be
able to tell if I have a prayer of delivering sufficient drive current,
though I'd still prefer to test on real hardware before having a bunch of
boards manufactured.
Vince
1:49 a.m.
Some place in the pdp-8E/M docs there must be specs
for the TTY and
reader control circuits. Take a look at the TTY I/O prints and see
what devices DEC used to drive the relay circuit.
The circuit used in e/m machines appears to be overkill -- it can drive
100ma, and kinda had me worried. I rechecked the circuit used in the 8L,
and it looks set up for about 30ma. I can do that without too much trouble.
If I can't find a TTY to test with, I'll just spec the resister value for
30ma and hope it works out :-).
Vince
1:57 a.m.
Some place in
the pdp-8E/M docs there must be specs for the TTY and
reader control circuits. Take a look at the TTY I/O prints and see
what devices DEC used to drive the relay circuit.
The circuit used in e/m machines appears to be overkill -- it can drive
100ma, and kinda had me worried. I rechecked the circuit used in the 8L,
and it looks set up for about 30ma. I can do that without too much If I can't find a TTY to test with, I'll just
spec the resister value for
30ma and hope it works out :-).
I take that back. Looking more closely, the return for that circuit is
to -15, not ground. That puts it squarely at 100ma in both cases, which is
more than my circuit can do (50ma).
Vince
1 Dec
1 Dec
8:25 a.m.
I take that back. Looking more closely, the return for that circuit is
to -15, not ground. That puts it squarely at 100ma in both cases, which
is
more than my circuit can do (50ma).
Vince
Sorry about the delay...I'm afraid its 100ma, apparently there is
a R/C network across the relay, I go a reading of 196 ohms
(close enough to 200 ohms to call it that). This may be a
'fast acting' relay of higher ohmage, but the circuit might be
designed for a worst case of character by character control.
I'm afraid it's back to the drawing board.....
Mike
9:40 a.m.
Sorry about the delay...I'm afraid its 100ma,
apparently there is
a R/C network across the relay, I go a reading of 196 ohms
(close enough to 200 ohms to call it that). This may be a
'fast acting' relay of higher ohmage, but the circuit might be
designed for a worst case of character by character control.
I'm afraid it's back to the drawing board.....
That is just weird. According to my calculations, DEC's circuit applies
15.7V across this relay and it's series resistor, with at most 57ma before
the components exceed their ratings. 15V/200 ohms = 75ma, so the circuit
can't work like that
I was expecting *at least* 300 ohms for the relay and it's series resistor.
Did you measure at the relay, or at the cable?
Assuming what you say is true, the 0.7V supply will be drug below ground,
and the whole circuit will draw 20V/350 ohms = 57.1ma. That puts the
components right at their operational limits, but might actually be the way
things work.
Vince
11:09 a.m.
----- Original Message -----
From: "vrs" <vrs(a)msn.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk(a)classiccmp.org>
Sent: Monday, December 01, 2003 6:40 PM
Subject: Re: W076/M452 replacement cards
resistor.
Sorry about
the delay...I'm afraid its 100ma, apparently there is
a R/C network across the relay, I go a reading of 196 ohms
(close enough to 200 ohms to call it that). This may be a
'fast acting' relay of higher ohmage, but the circuit might be
designed for a worst case of character by character control.
I'm afraid it's back to the drawing board.....
That is just weird. According to my calculations, DEC's circuit applies
15.7V across this relay and it's series resistor, with at most 57ma before
the components exceed their ratings. 15V/200 ohms = 75ma, so the circuit
can't work like that
I was expecting *at least* 300 ohms for the relay and it's series Did you measure at the relay, or at the cable?
Assuming what you say is true, the 0.7V supply will be drug below ground,
and the whole circuit will draw 20V/350 ohms = 57.1ma. That puts the
components right at their operational limits, but might actually be the
way
things work.
Vince
I measured at the cable. I acted like there is a R/C network across the
relay,
that is the reading went up over several seconds to just under 200 ohms. It
appears that there may not be just a simple relay.
Mike
11:41 a.m.
I measured at the cable. I acted like there is a R/C
network across the
relay,
that is the reading went up over several seconds to just under 200 ohms.
It
appears that there may not be just a simple relay.
Hmm. I am going by "Figure 5-7 Teletype Connections", which led me to
expect Relay+ to be connected to the relay, and to the cathode of a diode.
I expected Relay- to be connected to the anode, and also to a resistor,
which connects to the other side of the relay. It shows a capacitor across
the relay contacts, which also connect to the local switch and the reader
solenoid.
I don't suppose I could prevail upon you to trace the connections/schematic
for me?
Thanks!
Vince
2 Dec
2 Dec
11:19 a.m.
Hmm. I am going by "Figure 5-7 Teletype
Connections", which led me to
expect Relay+ to be connected to the relay, and to the cathode of a diode.
I expected Relay- to be connected to the anode, and also to a resistor,
which connects to the other side of the relay. It shows a capacitor
across
the relay contacts, which also connect to the local
switch and the reader
solenoid.
I don't suppose I could prevail upon you to trace the
connections/schematic
for me?
Thanks!
Vince
It was just as you describe except the capacitor is a MOV on mine,
except there was a 10mf cap across the relay coil, that micht have
been a non-DEC FCO and from tha soldering job I know who did
it. The relay is a reed relay marked as 12vdc coil and measured
328 ohms which works out to about 37ma. BTW the run relay
is mounted on a small PCB mounted vertically near the left end
of the keyboard assy. There are four wires that run back into the
rats nest at the rear of the PS.
Mike
11:38 a.m.
It was just as you describe except the capacitor is a
MOV on mine,
except there was a 10mf cap across the relay coil, that micht have
been a non-DEC FCO and from tha soldering job I know who did
it. The relay is a reed relay marked as 12vdc coil and measured
328 ohms which works out to about 37ma. BTW the run relay
is mounted on a small PCB mounted vertically near the left end
of the keyboard assy. There are four wires that run back into the
rats nest at the rear of the PS.
Excellent. Not sure that capacitor is a good idea. The rest sounds similar
to what I expected.
For better or for worse, I just ordered the W076 replacement boards made. I
had ordered the M452 replacements yesterday, and today the board shop said
the files were OK for their equipment. Hopefully the same thing will happen
with the W076 artwork (but more quickly -- I had to resubmit the silkscreen
for the M452 replacement twice :-)).
Vince
3 Dec
3 Dec
5:23 a.m.
--snip--
Excellent. Not sure that capacitor is a good idea. The rest sounds
similar
I didn't thinks so either, so I removed it...most likely should have
been a .01 mf...or was a 'fix' for a problem with the host. I spent
a year removing this guys 'fixes' and then correcting the original problem.
For better or for worse, I just ordered the W076 replacement boards made.
I
had ordered the M452 replacements yesterday, and today
the board shop said
the files were OK for their equipment. Hopefully the same thing will
happen
with the W076 artwork (but more quickly -- I had to
resubmit the
silkscreen
for the M452 replacement twice :-)).
Vince
Glad to hear that, I look foward to seeing the finished boards.
Mike
29 Nov
29 Nov
1:22 a.m.
New subject: Looking for...old mobo with AGP
Hello, all:
I was wondering if in the vast storehouse of random parts that we all keep
if someone has a spare Socket 7 (Pentium 233) motherboard *with* an AGP slot
that I can use for a MAME project (allowing maximum reuse of my CPU/memory
parts). I have several older motherboards but none with AGP that I can use
with the ArcadeVGA board (a VGA board made specially for use with arcade
monitors).
Alternatively, I could use any ATX form factor motherboard with an AGP slot
so long as it doesn't have an integrated video card. It's getting harder to
find cheap motherboards without integrated VGA, and searching eBay is very
tedious. This is a perfect "older technology" project.
If anyone has something that might work, please contact me off list.
Thanks.
Rich
Rich Cini
Collector of classic computers
Build Master for the Altair32 Emulation Project
Web site: http://highgate.comm.sfu.ca/~rcini/classiccmp/
/************************************************************/
5:09 a.m.
New subject: Looking for...old mobo with AGP
Hello, all:
I was wondering if in the vast storehouse of random parts that we
all keep
if someone has a spare Socket 7 (Pentium 233) motherboard *with* an
AGP slot that I can use for a MAME project (allowing maximum reuse
of my CPU/memory parts). I have several older motherboards but none
with AGP that I can use with the ArcadeVGA board (a VGA board made
specially for use with arcade monitors).
Alternatively, I could use any ATX form factor motherboard with an
AGP slot
Try ALi chipset-based motherboards it has AGP slot & socket 7. SiS
did made one but this is harder to find.
Otherwise slot 1, found either ATX or baby AT factors and it is best
compatiablity for OSes especially the BX and LX (old PII 233, 266,
300 & 333 also for any old 2.0V 66MHz fsb celerons). Most easier to
find.
Cheers,
Wizard
5:14 a.m.
New subject: Looking for...old mobo with AGP
if someone has a spare Socket 7 (Pentium 233)
motherboard *with* an AGP slot
that I can use for a MAME project (allowing maximum reuse of my CPU/memory
Depending on what you're trying to run, a Pentium 233 might not have enough speed.
I'd built a Pentium II box with this in mind prior to buying a real Neo Geo arcade
machine, and it just didn't have the speed needed. I'd recommend a mid-range
Pentium III.
Zane
--
--
| Zane H. Healy | UNIX Systems Administrator |
| healyzh(a)aracnet.com (primary) | OpenVMS Enthusiast |
| | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| PDP-10 Emulation and Zane's Computer Museum. |
| http://www.aracnet.com/~healyzh/ |
5:23 a.m.
New subject: Looking for...old mobo with AGP
No, no. P-II's lack the power too. Go for an AMD Athlon 850-1Ghz box with
about 256MB RAM or more. Like some of the original socket a's. Those would
be the cheapest best bang for the buck solution. I've run across too many
P-III's that just don't stand up after the customer unloads their wallet
into it where they could have saved a wad going older athlon.
-John
At 02:14 PM 11/29/2003, you wrote:
----------------------------------------
Founder, Lead Writer, Tech Analyst
and Web Designer Boff-Net Technologies
http://boff-net.dhs.org/index.html
---------------------------------------
if someone has
a spare Socket 7 (Pentium 233) motherboard *with* an AGP slot
that I can use for a MAME project (allowing maximum reuse of my CPU/memory
Depending on what you're trying to run, a Pentium 233 might not have
enough speed. I'd built a Pentium II box with this in mind prior to
buying a real Neo Geo arcade machine, and it just didn't have the speed
needed. I'd recommend a mid-range Pentium III.
Zane
--
--
| Zane H. Healy | UNIX Systems Administrator |
| healyzh(a)aracnet.com (primary) | OpenVMS Enthusiast |
| | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| PDP-10 Emulation and Zane's Computer Museum. |
| http://www.aracnet.com/~healyzh/ |
5:47 a.m.
New subject: Looking for...old mobo with AGP
>Depending on what you're trying to run, a
Pentium 233 might not have
>enough speed. I'd built a Pentium II box with this in mind prior to
>buying a real Neo Geo arcade machine, and it just didn't have the speed
>needed. I'd recommend a mid-range Pentium III.
I actually have a test system running now and it works pretty well. The key
is to use the DOS version or MAME32 under Windows 95/95SR2 only. The later
versions have the "shell update" which essentially uses Internet Explorer
components as the shell.
Rich Cini
Collector of classic computers
Build Master for the Altair32 Emulation Project
Web site: http://highgate.comm.sfu.ca/~rcini/classiccmp/
/************************************************************/
-----Original Message-----
From: cctalk-bounces(a)classiccmp.org
[mailto:cctalk-bounces@classiccmp.org]On Behalf Of Zane H. Healy
Sent: Saturday, November 29, 2003 2:14 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Looking for...old mobo with AGP
if someone has a spare Socket 7 (Pentium 233)
motherboard *with* an AGP
slot
that I can use for a MAME project (allowing maximum
reuse of my CPU/memory
Depending on what you're trying to run, a Pentium 233 might not have enough
speed. I'd built a Pentium II box with this in mind prior to buying a real
Neo Geo arcade machine, and it just didn't have the speed needed. I'd
recommend a mid-range Pentium III.
Zane
--
--
| Zane H. Healy | UNIX Systems Administrator |
| healyzh(a)aracnet.com (primary) | OpenVMS Enthusiast |
| | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| PDP-10 Emulation and Zane's Computer Museum. |
| http://www.aracnet.com/~healyzh/ |
5:59 a.m.
New subject: Looking for...old mobo with AGP
Rich,
Look for a FIC 503+. That's what I have in my PC, and it'll go to about
400 or 500mhz depending on bios revision. It does have an AGP slot.
along with PCI and ISA. Also, it also uses an AT form factor layout, so
you can use alnost any old PC case, if you'll be using one at all.
Chad Fernandez
Michigan, USA
27 Nov
27 Nov
9:34 a.m.
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3:52 p.m.
> > > Is it that easy to mod the TTY? Where
do you get the relay?
> >
> > The instructions for doing this are in at least one DEC printest,
similar
> > instructions are in the Intel MCS8i manual,
and doubtless elsewhere.
>
> I found them. I'd still need relay part number 4915. There are also
some
things called
"thyractors" called for.
IIRC, a thyractor is some kind of overvoltage clamping device. You could
probably replace it with a pair of zener diodes in inverse series, or
with a VDR. >
> > No idea where you'd get the relay these days. I wonder if you could
> > design a solid-state switching circuit that would work, with an
> > opto-isolator on the input
>
> Maybe, if I had specs for the relay. If I had the specs, I might even
be
able to tell
if I have a prayer of delivering sufficient drive current,
I have no idea what the official spec is, but the DEC cards didn't supply
that much current (I would guess at less than 100mA, but that is a guess). > though I'd still prefer to test on real
hardware before having a bunch
of
boards
manufactured.
Agreed.... Pity my ASR33 is almost impossible to get to, or I'd measure
the relay coil current for you (mine has an official DEC modification PCB
in it).
-tony
28 Nov
28 Nov
9:52 a.m.
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10:37 a.m.
Personally, I'd design the card to be able to
switch 100mA with an
output voltage of 20V (IIRC DEC ran the relay between the +5V and -15V
rails). Maybe overkill, but I'd be suprised if it didn't work...
Actually, DEC derives a +0.7V supply with a 150 ohm resistor and some
diodes, then uses a transistor to close the switch between *that* and -15V
through the teletype mod. This is the 150 ohm resistor only rated for 57ma.
Moreover, *another* diode clamps the reader enable line to ground, so the
actual voltage on the positive side of the reader run option is at most one
diode drop above ground. I have no idea why the reader run circuit is run
from with 15.7V instead of 15V, unless the drop across
the transistor is
supposed to leave 15V for the reader run circuit. That, in turn,
would
imply that the reader run circuit won't run on, say, 14.3V, which is only 5%
under. A circuit with less than a 5% margin seems like it would be flaky
over long cables, etc.
All of which just convinces me I don't understand the issues well enough to
bet on the results.
I have a redesigned version of the circuit, but with no way to test either
one, the situation is still not satisfactory. If I have to build it without
testing, it would be reassuring to at least know what the schematic of the
reader-run option is. I have the LT33 drawings, but they don't have a
schematic (with parts values) there. More like a picture of the thing, with
some cryptic notes about it.
Vince
7452
days inactive
7461
days old
24 comments
8 participants
participants (8)
-
ard＠p850ug1.demon.co.uk -
cukr＠massnet1.net -
fernande＠internet1.net -
healyzh＠aracnet.com -
john_boffemmyer_iv＠boff-net.dhs.org -
jpero＠sympatico.ca -
rcini＠optonline.net -
vrs＠msn.com