14 Jan
2004
14 Jan
'04
2:23 p.m.
If it uses standard chips (i.e. data sheets exist),
then it can be
reverse-engineered!
Not if the uCode proms have rotted.
15 Jan
15 Jan
11:50 a.m.
Not if the uCode proms have rotted.
I thought 2900 designs usually used fuse link proms as the eproms of the
era weren't fast enough. 
18 Jan
18 Jan
10:55 a.m.
:-)). In fact, I read somewhere that the PROMs can
suffer
from bit-rot
where the fuses actually grow back. And of course the
transistors, etc,
in the address decoder and output buffers can fail.
A few years ago I had a customer issue with a DSW42
synch card in a MicroVAX 3100-85; just one particular
customer and one particular machine but with a group
of different DSW42s. After the usual fiddling around
I eventually reproduced the problem and sent a box
across the Atlantic to the h/w team who were doing
support for this. The answer came back that the PLD
(IIRC) was bad and they'd had a preliminary report
form the manufacturer indicating that for that
particular batch of the suspect part "crystal regrowth"
(or some similar phrase) was a known failure mode.
I think if you wait long enough all ICs will fail,
through solid-state diffusion if nothing else. At
least with the off-the-shelf parts it will be possible
(in principle) to remanufacture a facsimile. With
modern ASICs (and probably FPGAs) this will be pretty
hard to achieve.
Antonio
--
---------------
Antonio Carlini arcarlini(a)iee.org
3:32 p.m.
Antonio Carlini wrote:
I think if you wait long enough all ICs will fail,
through solid-state diffusion if nothing else. At
least with the off-the-shelf parts it will be possible
(in principle) to remanufacture a facsimile. With
modern ASICs (and probably FPGAs) this will be pretty
hard to achieve.
Antonio
But with TUBE computers you just fix the broken part.:)
That is the major difference between IC's and the earlier
generations of computers. That is part of the reason
real classic computers have a better chance of sticking
around, as you can still make parts like core memory
for a modest amount of $ compared to anything with a IC
in it.
Ben.
3:44 p.m.
Although it has been quite a while since I have seen many commercial firms
that will fabricate or repair core memory for anything like a reasonable
price....
-----Original Message-----
From: cctalk-bounces(a)classiccmp.org
[mailto:cctalk-bounces@classiccmp.org]On Behalf Of ben franchuk
Sent: Sunday, January 18, 2004 9:33 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Emulators of Classic Computers
Antonio Carlini wrote:
I think if you wait long enough all ICs will fail,
through solid-state diffusion if nothing else. At
least with the off-the-shelf parts it will be possible
(in principle) to remanufacture a facsimile. With
modern ASICs (and probably FPGAs) this will be pretty
hard to achieve.
Antonio
But with TUBE computers you just fix the broken part.:)
That is the major difference between IC's and the earlier
generations of computers. That is part of the reason
real classic computers have a better chance of sticking
around, as you can still make parts like core memory
for a modest amount of $ compared to anything with a IC
in it.
Ben.
4:24 p.m.
David V. Corbin wrote:
Although it has been quite a while since I have seen
many commercial firms
that will fabricate or repair core memory for anything like a reasonable
price....
Who said 'Commercial' any where in the post.
Many people collect and repair classic computers
for the LOVE of doing it.
Ben.
4:37 p.m.
Do you know of ANYONE who has the proper tools for re-threading a core
plane?
The last contact I had was a small manufacturing company here on LI, but
that dried up about 8 years ago.
-----Original Message-----
From: cctalk-bounces(a)classiccmp.org
[mailto:cctalk-bounces@classiccmp.org]On Behalf Of ben franchuk
Sent: Sunday, January 18, 2004 10:25 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Emulators of Classic Computers
David V. Corbin wrote:
Although it has been quite a while since I have seen
many commercial firms
that will fabricate or repair core memory for anything like a reasonable
price....
Who said 'Commercial' any where in the post.
Many people collect and repair classic computers
for the LOVE of doing it.
Ben.
4:48 p.m.
On Sun, 18 Jan 2004, David V. Corbin wrote:
Do you know of ANYONE who has the proper tools for
re-threading a core
plane?
PRODUCTION? NO.
Repair of a single core plan? Absolutely!
The size of the beads will determine what size
needle threaded with wire to use.
Early planes used beads so large that you can re-thread t
hem with sewing needles!
19 Jan
19 Jan
10:23 a.m.
Repair of a single core plan? Absolutely!
The size of the beads will determine what size
needle threaded with wire to use.
Early planes used beads so large that you can re-thread t
hem with sewing needles!
Core planes are (were) often threaded without needles - there just wasn't
enough room in each core for a needle once the first two (or three) wires
were strung. The wire itself is the needle. IBM invented a very simple
solution - the wire to be strung was simply pulled apart gently. At the
break was a nicley formed taper.
William Donzelli
aw288(a)osfn.org
12:55 p.m.
How do you get off this list???
-----Original Message-----
From: cctech-bounces(a)classiccmp.org
[mailto:cctech-bounces@classiccmp.org] On Behalf Of William Donzelli
Sent: Monday, January 19, 2004 1:23 PM
To: General Discussion: On-Topic and Off-Topic Posts
Cc: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: Emulators of Classic Computers
Repair of a single core plan? Absolutely!
The size of the beads will determine what size
needle threaded with wire to use.
Early planes used beads so large that you can re-thread t
hem with sewing needles!
Core planes are (were) often threaded without needles - there just
wasn't
enough room in each core for a needle once the first two (or three)
wires
were strung. The wire itself is the needle. IBM invented a very simple
solution - the wire to be strung was simply pulled apart gently. At the
break was a nicley formed taper.
William Donzelli
aw288(a)osfn.org
4:28 p.m.
New subject: ATTN: ronbain...
On Mon, 2004-01-19 at 18:55, ronbain wrote:
How do you get off this list???
Well...
You could look at the email address that sent you the email, and find
out the domain name (classiccmp.org).
Then you could type into the address bar of your chosen web browser that
domain name with a "www." in front of it (www.classiccmp.org).
Then follow the link that says "Mailing Lists" at the top of the web
page.
Then follow the link that says "cctalk", since from the address your
post comes from it seems you are subscribed to the "cctalk" list.
Then fill in your email address in the box labeled "Subscription Options
/ Unsubscribe" and click the "Unsubscribe or edit options" button, and
follow the instructions you get from there.
If you can't follow these instructions, I can't help you any further,
but continued repeated postings of "how do you get off this list"
probably isn't going to endear you to anyone.
Next time you subscribe to a mailing list, keep the emails from the list
telling you how to unsubscribe. Then you won't have to keep asking...
20 Jan
20 Jan
8:30 a.m.
New subject: ATTN: ronbain...
Next time you subscribe to a mailing list, keep the
emails from the
list telling you how to unsubscribe. Then you >won't have to
keep
asking...
Or just look at the message headers on any message from the list!
Antonio
--
---------------
Antonio Carlini arcarlini(a)iee.org
18 Jan
18 Jan
4:54 p.m.
New subject: Classic Computers - Classic parts
David V. Corbin wrote:
Do you know of ANYONE who has the proper tools for
re-threading a core
plane?
The last contact I had was a small manufacturing company here on LI, but
that dried up about 8 years ago.
No, now may be the time to do the leg work and collect the tools. I am
sure that core memory can be repaired but it needs to be done under a
microscope with fine tools.
People who use core memory, I don't think have a the knowlage of where
or how to find replacement parts since most core memory is chopped up
for sale on ebay. :( Does anybody have a stockpile of cores and driver
transitors and driver IC's.
Ben.
4:54 p.m.
New subject: Core memory repair
"David V. Corbin" wrote:
Do you know of ANYONE who has the proper tools for re-threading a core
plane?out 8 years ago.
I sold some DataRam Core memory modules a couple of years ago, and did
some searching for information. While I don't remember the contact, I do
remember the process :). I called DataRam and they gave me the number of
someone who sold and maintained their old core memory products. This was
in 1999 or so IIRC.
19 Jan
19 Jan
11:47 a.m.
But with TUBE computers you just fix the broken
part.:)
That is the major difference between IC's and the earlier
generations of computers. That is part of the reason real
classic computers have a better chance of sticking around,
as you can still make parts like core memory for a modest
amount of $ compared to anything with a IC in it. Ben.
Tubes are still being manufactured, but 50 years from now,
will they still be made? If not, how feasible would it be
to make a replacement for an existing tube (assume a common
tube where characteristics are known) as a hobbyist?
The early ICs, I would guess, were simple enough that,
given the specs, you could knock up a work-a-like from
modern parts.
I agree that, from the restorer's point of view, modern
parts (FPGAs, ASICs etc.) are hard to replace. But that's
just because the internal structure is not known (and that
matters for FPGAs). If you did know how a given FPGA was
constructed internally, I expect you could "emulate" it
with one from a few generations later.
Antonio
--
---------------
Antonio Carlini arcarlini(a)iee.org
12:27 p.m.
Tubes are still being manufactured, but 50 years from
now,
will they still be made?
Very few types are still being made. I do not think anyone is making
computer grade tubes - the DOD still has plenty left in the depots.
If not, how feasible would it be
to make a replacement for an existing tube (assume a common
tube where characteristics are known) as a hobbyist?
Quite easy. It has been done already for the old radio folks. There are
little wafers that slip right under a 201 (or WD11) that contains a FET
and contacts for the pins of the tube that pass thru the wafer. These
work quite well, so duds can be used quite well, and the look of the
radio is maintained (along with the filaments' light and heat).
Of course, FETrons were commercially available solid state tube
replacements from the 1960s and 70s - they can still be found, and come
in many models, emulating quite a few complex types. The disadvantage is
that the old tube must be removed, along with that glow.
William Donzelli
aw288(a)osfn.org
8:47 p.m.
Making a replacement for a tube is easy, as long as you don't require it
to look like a tube.
On Mon, 2004-01-19 at 14:47, Antonio Carlini wrote:
But with TUBE
computers you just fix the broken part.:)
That is the major difference between IC's and the earlier
generations of computers. That is part of the reason real
classic computers have a better chance of sticking around,
as you can still make parts like core memory for a modest
amount of $ compared to anything with a IC in it. Ben.
Tubes are still being manufactured, but 50 years from now,
will they still be made? If not, how feasible would it be
to make a replacement for an existing tube (assume a common
tube where characteristics are known) as a hobbyist?
The early ICs, I would guess, were simple enough that,
given the specs, you could knock up a work-a-like from
modern parts.
I agree that, from the restorer's point of view, modern
parts (FPGAs, ASICs etc.) are hard to replace. But that's
just because the internal structure is not known (and that
matters for FPGAs). If you did know how a given FPGA was
constructed internally, I expect you could "emulate" it
with one from a few generations later.
Antonio
8:38 p.m.
On Sun, 2004-01-18 at 18:32, ben franchuk wrote:
But with TUBE computers you just fix the broken part.:)
That is the major difference between IC's and the
earlier
generations of computers. That is part of the reason
real classic computers have a better chance of sticking
around, as you can still make parts like core memory
for a modest amount of $ compared to anything with a IC
in it.
Actually there's a interesting lesson in here, in that in the tube days
the components -- though manifold and balky -- were common, cheap,
easily substituted, and maint problems are largely the sheer number of
tiny, stupid parts. Any given part is easily re-fabricated, but sheesh
there's so damn many of them.
I have a new design (yes you read right) for a tube computer, probably
75 envelopes, on my website. 20 bits, serial arith, drum memory but I
later realized that switched-capacitor (aka DRAM) was actually
historically acceptable since one was made (NBS "test" computer; the
diodes were too expensive in 1952 but it was basically just a DRAM).
Somehow, I can't find the money to make it. But I'm serious enough,
there's an assembler and simulator there (wps.com/projects).
8:51 p.m.
On 19 Jan 2004, Tom Jennings wrote:
I have a new design (yes you read right) for a tube
computer, probably
75 envelopes, on my website. 20 bits, serial arith, drum memory but I
Too cool. This is a dream of mine as well but (sigh) time is so short.
Man, Tom, you are one of the coolest people alive :)
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
20 Jan
20 Jan
4:48 a.m.
Quothe Tom Jennings, from writings of Mon, Jan 19, 2004 at 11:29:08PM -0800:
On Sun, 2004-01-18 at 18:32, ben franchuk wrote:
But with TUBE computers you just fix the broken part.:)
Oh really? :-) When was the last time that you saw someone pop open a
tube and replace or repair an open filament, repair a short between
elements or restore the vacuum in a gassy tube, etc., and then put the
tube back into use?
I have a new design (yes you read right) for a tube
computer, probably
75 envelopes, on my website. 20 bits, serial arith, drum memory but I
later realized that switched-capacitor (aka DRAM) was actually
historically acceptable since one was made (NBS "test" computer; the
diodes were too expensive in 1952 but it was basically just a DRAM).
Neat! Slow, but most interesting.
Somehow, I can't find the money to make it. But
I'm serious enough,
there's an assembler and simulator there (wps.com/projects).
What appears to be the most expensive aspect of the project thus far?
--
Copyright (C) 2003 R. D. Davis The difference between humans & other animals:
All Rights Reserved an unnatural belief that we're above Nature &
rdd(a)rddavis.org 410-744-4900 her other creatures, using dogma to justify such
http://www.rddavis.org beliefs and to justify much human cruelty.
9:21 a.m.
R. D. Davis wrote:
The sockets :)
6N16B-V are computer tubes.
http://www.russiantubes.com/sale.php
>I have a new design (yes you read right) for a tube computer, probably
>75 envelopes, on my website. 20 bits, serial arith, drum memory but I
>later realized that switched-capacitor (aka DRAM) was actually
>historically acceptable since one was made (NBS "test" computer; the
>diodes were too expensive in 1952 but it was basically just a DRAM).
Somehow, I
can't find the money to make it. But I'm serious enough,
there's an assembler and simulator there (wps.com/projects).
What appears to be the most expensive aspect of the project thus far?
22 Jan
22 Jan
11:47 a.m.
On Tue, 2004-01-20 at 12:21, ben franchuk wrote:
No sh*t! There are however plenty of computer tubes around, the 5xxx and
6xxx series. Since the clock is slow I chose high-speed dekatrons to
generate the 20 bit times (bit0 - bit 17, dead0, dead1), and clock and
memory busses would probably require some 6L6's as cathode followers,
that sort of stuff, but most of the tubes are available and with
sufficient design margins, not hard to keep running.
A major problem in ye olden dayes were crappy power supplies. I figured
I'm use 100% solid-state power with a PIC to do sequencing and control,
which matters a lot for reliable tube stuff. Let's not be tooo
pedantic... :-)
What appears
to be the most expensive aspect of the project thus far?
The sockets :)
4:06 p.m.
No sh*t! There are however plenty of computer tubes
around, the 5xxx and
6xxx series. Since the clock is slow I chose high-speed dekatrons to
generate the 20 bit times (bit0 - bit 17, dead0, dead1), and clock and
memory busses would probably require some 6L6's as cathode followers,
6L6s may give you prolems - they are not computer rated (although for a
clock, it should not be a problem). 6005s (computer 6AQ5) is a good choice.
Cheap, too.
William Donzelli
aw288(a)osfn.org
20 Jan
20 Jan
9:48 a.m.
On Tue, 2004-01-20 at 07:45, R. D. Davis wrote:
SOrry, I misspoke, by 'repair' I meant 'replace'. Though my father had
an 01 (not 01A) tube with I swear an RCA base and a Westinghouse
envelope (seal on top of tube) or converse. I lost it as a kid (ouch).
But with TUBE
computers you just fix the broken part.:)
Oh really? :-) When was the last time that you saw someone pop open a
tube and replace or repair an open filament, repair a short between
elements or restore the vacuum in a gassy tube, etc., and then put the
tube back into use? > I have a new design (yes you read right) for a
tube computer, probably
> 75 envelopes, on my website. 20 bits, serial arith, drum memory
Neat! Slow, but most interesting.
Not even capable of keeping a 60 wpm tty at full tilt -- but few small
machines of the first gen could (eg. the LGP-21 took 7 seconds (7000 mS)
to checksum 64 contiguous words of memory). Relative speed is umm
relative.
> Somehow, I can't find the money to make it.
But I'm serious enough,
> there's an assembler and simulator there (wps.com/projects).
What appears to be the most expensive aspect of the
project thus far?
Prototype development I'd say. The remaining paper circuit design could
be done in "spare time". I have no pretense of being a better tube
designer than the greybeards. Reliability and work-first-time is to me
more important than speed, which mattered most 'back then', so dropping
margins (80 KHz clock) and fancy hardware (eg. no mult/div) and using 50
years of hindsight (eg. IO design!) and the fact the silicon diodes cost
$5/100, not $50 each (equiv $) makes that part doable.
Drum memory was scary though, I have a design (not on www) for a mthod
of construction, but it's still scary to construct. Switched-cap is
easier, and using a PC board you could get 500 cells per PCB easy, likel
1024 (big 2-sided boards) and with 20 of those you'd have a Kword.
4Kwords would be best. That's just a first-order conservative guess as
we didn't talk details on it.
12:50 p.m.
SOrry, I misspoke, by 'repair' I meant
'replace'. Though my father had
an 01 (not 01A) tube with I swear an RCA base and a Westinghouse
envelope (seal on top of tube) or converse. I lost it as a kid (ouch).
This is because Westinghouse made many (most, I think) of RCAs 201s. GE
made them as well.
Prototype development I'd say.
Have you obtained all of the tubes you need? I noticed on your websight
you mention using "Red Series" tubes. As you probably figured out, those
(RCA Red Line or Bendix Red Bank) are pretty expensive.
William Donzelli
aw288(a)osfn.org
22 Jan
22 Jan
11:55 a.m.
On Tue, 2004-01-20 at 15:50, William Donzelli wrote:
Have you obtained all of the tubes you need? I noticed
on your websight
you mention using "Red Series" tubes. As you probably figured out, those
(RCA Red Line or Bendix Red Bank) are pretty expensive.
THe electronic design was abandoned for now. Basically I was to
(will...?) build a 4 x 4 switched cap memory which will be a nice
reality check on flops, tubes, etc.
Also, I chased down and read the exhaustive life-testing book the US Mil
sponsored (forget the title) in the early 60's re: tube reliability.
Though it applied specifically to subminis, it quantified what the
computing people knew: derate, derate, derate. They got easily 16,000
hours from selected devices. The suspected more was easily possible, but
that was the extend of their testing. It was interesting that some
devices worked better/longer at slightly elevated Vff.
Also, if you look at general tube electronic environments throughout the
50's, excepting the smartest stuff (Tek scopes etc) the power supplies
are total crap. Unregulated and unsequenced. That did a lot of harm. It
was fine for radios but not for "high speed" switching where margins
started to matter.
4:01 p.m.
THe electronic design was abandoned for now. Basically
I was to
(will...?) build a 4 x 4 switched cap memory which will be a nice
reality check on flops, tubes, etc.
Please keep us informed.
Also, I chased down and read the exhaustive
life-testing book the US Mil
sponsored (forget the title) in the early 60's re: tube reliability.
Though it applied specifically to subminis, it quantified what the
computing people knew: derate, derate, derate. They got easily 16,000
hours from selected devices.
Subminis might also be a good choice, if you can find them. They "never"
go bad. I don't think I have ever found a bad one. Their reliabilty was
due to production in a clean room environment using very high purity
materials. One interesting side effect was that submini tubes lost their
sockets - the things were soldered right into the circuits, as the sockets
became the most failure prone components.
Most computer tubes were also built in the same clean room environment,
and also tended to be very reliable. In the good old tube computer days,
there would be a flurry of tube swapping for the first few months, maybe
a year, of the computer's life, but then as the weakling runt tubes were
purged, the machines became quite reliable.
The suspected more was easily possible, but
that was the extend of their testing. It was interesting that some
devices worked better/longer at slightly elevated Vff.
The biggest advancement was the use of the IERC tube shields - the type
that have ribbing inside to conduct the heat away. It took ten years, but
the industry finally figured out the old style tube shields were a really
dumb idea.
Also, if you look at general tube electronic
environments throughout the
50's, excepting the smartest stuff (Tek scopes etc) the power supplies
are total crap. Unregulated and unsequenced. That did a lot of harm. It
was fine for radios but not for "high speed" switching where margins
started to matter.
The military radar things, specifically for IFF systems, had good power
supplies. They were digital system, after all (specifially SIF encoders
and decoders).
William Donzelli
aw288(a)osfn.org
6:29 p.m.
On Thu, 22 Jan 2004, William Donzelli wrote:
IIRC, submini tubes were initially developed for use in proximity
fuses for anti-aircraft ammunition in WWII. I recall seeing some
during the early '40s that my Dad brought home from work - and
then took back. No need for sockets in a one use projectile!
- don
THe electronic
design was abandoned for now. Basically I was to
(will...?) build a 4 x 4 switched cap memory which will be a nice
reality check on flops, tubes, etc.
Please keep us informed.
Also, I chased down and read the exhaustive
life-testing book the US Mil
sponsored (forget the title) in the early 60's re: tube reliability.
Though it applied specifically to subminis, it quantified what the
computing people knew: derate, derate, derate. They got easily 16,000
hours from selected devices.
Subminis might also be a good choice, if you can find them. They "never"
go bad. I don't think I have ever found a bad one. Their reliabilty was
due to production in a clean room environment using very high purity
materials. One interesting side effect was that submini tubes lost their
sockets - the things were soldered right into the circuits, as the sockets
became the most failure prone components. Most computer tubes were also built in the same clean
room environment,
and also tended to be very reliable. In the good old tube computer days,
there would be a flurry of tube swapping for the first few months, maybe
a year, of the computer's life, but then as the weakling runt tubes were
purged, the machines became quite reliable.
The suspected more was easily possible, but
that was the extend of their testing. It was interesting that some
devices worked better/longer at slightly elevated Vff.
The biggest advancement was the use of the IERC tube shields - the type
that have ribbing inside to conduct the heat away. It took ten years, but
the industry finally figured out the old style tube shields were a really
dumb idea.
Also, if you look at general tube electronic
environments throughout the
50's, excepting the smartest stuff (Tek scopes etc) the power supplies
are total crap. Unregulated and unsequenced. That did a lot of harm. It
was fine for radios but not for "high speed" switching where margins
started to matter.
The military radar things, specifically for IFF systems, had good power
supplies. They were digital system, after all (specifially SIF encoders
and decoders).
William Donzelli
aw288(a)osfn.org
23 Jan
23 Jan
12:28 p.m.
> Subminis might also be a good choice, if you can
find them. They "never"
> go bad. I don't think I have ever found a bad one. Their reliabilty was
> due to production in a clean room environment using very high purity
> materials. One interesting side effect was that submini tubes lost their
> sockets - the things were soldered right into the circuits, as the sockets
SOemwhere I have a valved hearing aid. It uses 3 submini valves -- a pair
of DF64s in the first 2 stages and a DL64 in the output stage. These
valves are wire-ended, with 5 wires in line.
Howeverm they are plugged into little sockets inside -- I've seen the
same sockets, but with only 3 contacts fitted, used as transistor
sockets.
There were also sockets for the 8 pin subminis. I have one somewhere.
-tony
22 Jan
22 Jan
6:59 p.m.
Quothe William Donzelli, from writings of Thu, Jan 22, 2004 at
10:01:45PM -0500:
materials. One interesting side effect was that
submini tubes lost their
sockets - the things were soldered right into the circuits, as the sockets
became the most failure prone components.
One could always design some sort of spring-loaded sockets for them in
order to make them as useful as real tubes/valves. Without sockets,
circuitry containing them would be as annoying to repair as circuits
using non-socketed ICs.
--
Copyright (C) 2003 R. D. Davis The difference between humans & other animals:
All Rights Reserved an unnatural belief that we're above Nature &
rdd(a)rddavis.org 410-744-4900 her other creatures, using dogma to justify such
http://www.rddavis.org beliefs and to justify much human cruelty.
6:58 p.m.
One could always design some sort of spring-loaded
sockets for them in
order to make them as useful as real tubes/valves. Without sockets,
circuitry containing them would be as annoying to repair as circuits
using non-socketed ICs.
Very true, but the truth is that the damn things just never die.
Never common outside the government, these days subminis can be a little
difficult to find. Most of the time they are pretty cheap ($1 tubes, NIB,
at some lucky hamfests), simply because nobody needs them!
William Donzelli
aw288(a)osfn.org
23 Jan
23 Jan
1:11 p.m.
On Thu, 2004-01-22 at 19:01, William Donzelli wrote:
Will do!
THe electronic
design was abandoned for now. Basically I was to
(will...?) build a 4 x 4 switched cap memory which will be a nice
reality check on flops, tubes, etc.
Please keep us informed. Subminis might also be a good choice, if you can find
them. They "never"
go bad. I don't think I have ever found a bad one. Their reliabilty was
due to production in a clean room environment using very high purity
materials. One interesting side effect was that submini tubes lost their
sockets - the things were soldered right into the circuits, as the sockets
became the most failure prone components.
They are a good choice. The US gubbamint just (well a year or two ago)
dumped huge amounts of them, allegedly spares kept for existing equipme
nt went over 20 yrs old. There were some ship-board computers built with
them, soldered right into the PC board. Hell they're rugged, as they
were first developed for proximity fuzes in torpedos and shells!
Most computer tubes were also built in the same clean
room environment,
and also tended to be very reliable. In the good old tube computer days,
there would be a flurry of tube swapping for the first few months, maybe
a year, of the computer's life, but then as the weakling runt tubes were
purged, the machines became quite reliable.
I can totally see that scenario.
The biggest advancement was the use of the IERC tube
shields - the type
that have ribbing inside to conduct the heat away. It took ten years, but
the industry finally figured out the old style tube shields were a really
dumb idea.
Yeah, glass is a poor conductor of heat! I suppose lots of forced air
works too, but is always trouble.
The military radar things, specifically for IFF
systems, had good power
supplies. They were digital system, after all (specifially SIF encoders
and decoders).
See?! :-)
21 Jan
21 Jan
1:38 a.m.
But with TUBE
computers you just fix the broken part.:)
Oh really? :-) When was the last time that you saw someone pop open a
tube and replace or repair an open filament, repair a short between
elements or restore the vacuum in a gassy tube, etc., and then put the
tube back into use? 
1:52 a.m.
On Wed, 2004-01-21 at 12:38, William Maddox wrote:
I make no claims about the practicality of doing this for the small tubes
used in computers, but it used to be common to rebuild CRTs for TVs.
The setup for doing it was suitable for a small shop -- I recall TV service
oriented magazines containing ads for equipment to get into the rebuilding
business. I believe the point was to salvage the expensive glass bottle,
replacingthe entire electron gun. You removed the end of the neck, and
"welded" on a new one, then pumped the tube back down and sealed it
off.
--Bill
I seem to recall that although rebuilt tubes were fairly inexpensive (at
least in the late 1970s, early 1980s) the quality was rather variable.
TV tubes these days last so long, and the sets are so inexpensive (read:
cheap and nasty) that it's not really worth retubing conventional
televisions. Projection TVs are a different matter...
Gordon.
But with TUBE computers you just fix the broken
part.:)
Oh really? :-) When was the last time that you saw someone pop open a
tube and replace or repair an open filament, repair a short between
elements or restore the vacuum in a gassy tube, etc., and then put the
tube back into use?
15 Jan
15 Jan
11:41 a.m.
If it uses standard chips (i.e. data sheets
exist), then it can be
reverse-engineered!
Not if the uCode proms have rotted.
7487
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