Raytheon GA004 transistors, Digitronics 3500 Paper Tape read

E

Eric Smith

Guest
At the Computer History Museum (www.computerhistory.org), we're restoring
a DEC PDP-1 computer (www.pdp-1.org). In the process, we need to repair
a flaky amplifier channel in a Digitronics 3500 paper tape reader. We
isolated the fault to one channel. Each read amp board has three
transistors, two of which are marked Raytheon GA004, with a 1962 date
code. These appear to be PNP germanium transistors with a beta >100.
One of the transistors on the amplifier board that is failing seems
to have much higher leakage than the others.

Does anyone have a data sheet on this transistor, a cross reference,
or better yet some spares? We think we can probably get by with an
NTE102A, but we'd be happier to get an exact replacement or at least
enough technical data to prove to ourselves that the replacement we
choose will be satisfactory.

Also, if anyone has technical documentation or schematics for the
Digitronics (or IOMEC?) 3500 paper tape readers, we would really like to
obtain copies.

Thanks!
Eric Smith
PDP-1 Restoration Team
 
I wrote:
, a
cross reference, or better yet some spares? We think we can probably
get by with an NTE102A, but we'd be happier to get an exact
replacement or at least enough technical data to prove to ourselves
that the replacement we choose will be satisfactory.
Click to expand...
Michael A. Terrell wrote:
If you find a part that is in the same case style that works you
could try to re-mark it with the original part number.
Click to expand...
Actually, we don't really care what it looks like. If we can't get
the original Raytheon part (and I suspect we can't), we're perfectly
happy to use a more recent replacement, even if it's in a different
case style, as long as it's not too large to physically fit in the
available space.

What we're more interested in is finding out the specifications for
the original transistor, so we can tell whether any particular
candidate for replacement is actually suitable.

Re-marking some other transistor to look like a Raytheon part is
not required or even desirable. We do mark all the parts that
we replace, so that it is obvious that they are not the originals,
and we bag and label all of the removed parts.

Eric
 
Eric Smith wrote:

At the Computer History Museum (www.computerhistory.org), we're restoring
a DEC PDP-1 computer (www.pdp-1.org). In the process, we need to repair
a flaky amplifier channel in a Digitronics 3500 paper tape reader. We
isolated the fault to one channel. Each read amp board has three
transistors, two of which are marked Raytheon GA004, with a 1962 date
code. These appear to be PNP germanium transistors with a beta >100.
One of the transistors on the amplifier board that is failing seems
to have much higher leakage than the others.

Does anyone have a data sheet on this transistor, a cross reference,
or better yet some spares? We think we can probably get by with an
NTE102A, but we'd be happier to get an exact replacement or at least
enough technical data to prove to ourselves that the replacement we
choose will be satisfactory.

Also, if anyone has technical documentation or schematics for the
Digitronics (or IOMEC?) 3500 paper tape readers, we would really like to
obtain copies.

Thanks!
Eric Smith
PDP-1 Restoration Team
Send me your address and i will send you some Germanium PNP
Click to expand...
transisors. Betas seem to increase with current on all of them.
Have some new "bullet" JAN 2N128; beta seems to be about 40 at 4mA
and max 6V operating. Can get lots of these.
Have mixed old small cylindrical can, TO-1 or TO-44 (1 ea):
*unmarked (?RCA) good to about 50V; beta near 100 at 2mA.
*RCA 2N384 good to about 60V; beta near 75 at 2mA.
*RCA 2N406 good to about 20V; beta near 100 at 2mA.
*RCA 2N2613 good to about 20V; beta near 200 at 2mA.
*? B175 good to about 50V; beta near 200 at 2mA.
*NTE158 good to about 20V; beta near 120 at 2mA (obviously these can be
readily obtained).

*RCA TO-5 2N398 good to about 60V; beta near 100 at 2mA.
*RCA TO-5 2N247 good to about 60V; beta near 100 at 2mA.

Anyway i will send these to you on an "all or none" basis.
 
Eric Smith wrote:

At the Computer History Museum (www.computerhistory.org), we're restoring
a DEC PDP-1 computer (www.pdp-1.org). In the process, we need to repair
a flaky amplifier channel in a Digitronics 3500 paper tape reader. We
isolated the fault to one channel. Each read amp board has three
transistors, two of which are marked Raytheon GA004, with a 1962 date
code. These appear to be PNP germanium transistors with a beta >100.
One of the transistors on the amplifier board that is failing seems
to have much higher leakage than the others.

Does anyone have a data sheet on this transistor, a cross reference,
or better yet some spares? We think we can probably get by with an
NTE102A, but we'd be happier to get an exact replacement or at least
enough technical data to prove to ourselves that the replacement we
choose will be satisfactory.

Also, if anyone has technical documentation or schematics for the
Digitronics (or IOMEC?) 3500 paper tape readers, we would really like to
obtain copies.

Thanks!
Eric Smith
PDP-1 Restoration Team
I forgot to say that i had refurbished a paper tape reader that used
Click to expand...
photo-diodes and Ge PNPs; changed it from a "step" read to a continuous
or off/on read and added the sprocket hole as a sync channel using the
same photo-diodes but used comparitors.
Made a new PCB that was plugin compatible and changed the voltage
from -48V to +5V.
Speed increased from i step per second to feet per second.

The PCB in your reader should be simple enough to chase it out and
draw your own schematic if necessary That is what i had done).
 
Robert Baer <robertbaer@earthlink.net> writes:
I forgot to say that i had refurbished a paper tape reader that
used photo-diodes and Ge PNPs; changed it from a "step" read to a
continuous or off/on read and added the sprocket hole as a sync
channel using the same photo-diodes but used comparitors.
Click to expand...
Cool! The Digitronics 3500 is rated at 400 lines per second. I'm not
quite sure whether the interface is "step" or "continuous". The PDP-1 can
definitely make it read one line at a time, but when the PDP-1 read-in mode
is used, or software is used that doesn't have a significant delay between
the tape read instructions, it appears to operate continuously at the
rated 400 lines per second.

Made a new PCB that was plugin compatible and changed the voltage
from -48V to +5V.
Speed increased from i step per second to feet per second.
Click to expand...
Cool!

The PCB in your reader should be simple enough to chase it out and
draw your own schematic if necessary That is what i had done).
Click to expand...
We may do that at next week's team meeting. It's my understanding that
we expect to desolder both the suspected bad GA004, and one that is
believed to be working properly, and look at both on a curve tracer.

Eric
 
"Eric Smith" <eric@brouhaha.com> wrote in message
news:qhfyxcdt3h.fsf@ruckus.brouhaha.com...
At the Computer History Museum (www.computerhistory.org), we're
restoring
a DEC PDP-1 computer (www.pdp-1.org). In the process, we need to
repair
a flaky amplifier channel in a Digitronics 3500 paper tape reader. We
isolated the fault to one channel. Each read amp board has three
transistors, two of which are marked Raytheon GA004, with a 1962 date
code. These appear to be PNP germanium transistors with a beta >100.
One of the transistors on the amplifier board that is failing seems
to have much higher leakage than the others.

Does anyone have a data sheet on this transistor, a cross reference,
or better yet some spares? We think we can probably get by with an
NTE102A, but we'd be happier to get an exact replacement or at least
enough technical data to prove to ourselves that the replacement we
choose will be satisfactory.

Also, if anyone has technical documentation or schematics for the
Digitronics (or IOMEC?) 3500 paper tape readers, we would really like
to
obtain copies.
Click to expand...
The 2N1305 or similar one in that series were a common part in those
years. As you said, a NTE germanium should work okay, since it's in an
electromechanical device which probably doesn't put that great a demand
on the transistors. Also, you might consider swapping two transistors
so that the leaky one is in a later or less critical stage. But it may
get worse as time goes on, so it should be replaced.

Thanks!
Eric Smith
PDP-1 Restoration Team
Click to expand...
 
"Robert Baer" <robertbaer@earthlink.net> wrote in message
news:M6_be.465$HL2.257@newsread3.news.pas.earthlink.net...
Eric Smith wrote:

At the Computer History Museum (www.computerhistory.org), we're
restoring
a DEC PDP-1 computer (www.pdp-1.org). In the process, we need to
repair
a flaky amplifier channel in a Digitronics 3500 paper tape reader.
We
isolated the fault to one channel. Each read amp board has three
transistors, two of which are marked Raytheon GA004, with a 1962
date
code. These appear to be PNP germanium transistors with a beta
100.
One of the transistors on the amplifier board that is failing seems
to have much higher leakage than the others.

Does anyone have a data sheet on this transistor, a cross reference,
or better yet some spares? We think we can probably get by with an
NTE102A, but we'd be happier to get an exact replacement or at least
enough technical data to prove to ourselves that the replacement we
choose will be satisfactory.

Also, if anyone has technical documentation or schematics for the
Digitronics (or IOMEC?) 3500 paper tape readers, we would really
like to
obtain copies.

Thanks!
Eric Smith
PDP-1 Restoration Team
Send me your address and i will send you some Germanium PNP
transisors. Betas seem to increase with current on all of them.
Have some new "bullet" JAN 2N128; beta seems to be about 40 at 4mA
and max 6V operating. Can get lots of these.
Have mixed old small cylindrical can, TO-1 or TO-44 (1 ea):
*unmarked (?RCA) good to about 50V; beta near 100 at 2mA.
*RCA 2N384 good to about 60V; beta near 75 at 2mA.
*RCA 2N406 good to about 20V; beta near 100 at 2mA.
*RCA 2N2613 good to about 20V; beta near 200 at 2mA.
*? B175 good to about 50V; beta near 200 at 2mA.
*NTE158 good to about 20V; beta near 120 at 2mA (obviously these can
be
readily obtained).

*RCA TO-5 2N398 good to about 60V; beta near 100 at 2mA.
Click to expand...
This was used as a neon lamp driver, and should be capable of a lot
higher voltage than 60V. Manual says 105V.

Of course nowadays a high voltage germanium looks pitiful and pathetic
compared to a silicon transistor.

*RCA TO-5 2N247 good to about 60V; beta near 100 at 2mA.

Anyway i will send these to you on an "all or none" basis.
Click to expand...
 
Eric Smith wrote:
At the Computer History Museum (www.computerhistory.org), we're restoring
a DEC PDP-1 computer (www.pdp-1.org). In the process, we need to repair
a flaky amplifier channel in a Digitronics 3500 paper tape reader. We
isolated the fault to one channel. Each read amp board has three
transistors, two of which are marked Raytheon GA004, with a 1962 date
code. These appear to be PNP germanium transistors with a beta >100.
One of the transistors on the amplifier board that is failing seems
to have much higher leakage than the others.

Does anyone have a data sheet on this transistor, a cross reference,
or better yet some spares? We think we can probably get by with an
NTE102A, but we'd be happier to get an exact replacement or at least
enough technical data to prove to ourselves that the replacement we
choose will be satisfactory.

Also, if anyone has technical documentation or schematics for the
Digitronics (or IOMEC?) 3500 paper tape readers, we would really like to
obtain copies.

Thanks!
Eric Smith
PDP-1 Restoration Team
Click to expand...

If you find a part that is in the same case style that works you
could try to re-mark it with the original part number.

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida
 
Watson A.Name - "Watt Sun, the Dark Remover" wrote:

"Robert Baer" <robertbaer@earthlink.net> wrote in message
news:M6_be.465$HL2.257@newsread3.news.pas.earthlink.net...

Eric Smith wrote:


At the Computer History Museum (www.computerhistory.org), we're

restoring

a DEC PDP-1 computer (www.pdp-1.org). In the process, we need to

repair

a flaky amplifier channel in a Digitronics 3500 paper tape reader.

We

isolated the fault to one channel. Each read amp board has three
transistors, two of which are marked Raytheon GA004, with a 1962

date

code. These appear to be PNP germanium transistors with a beta

100.

One of the transistors on the amplifier board that is failing seems
to have much higher leakage than the others.

Does anyone have a data sheet on this transistor, a cross reference,
or better yet some spares? We think we can probably get by with an
NTE102A, but we'd be happier to get an exact replacement or at least
enough technical data to prove to ourselves that the replacement we
choose will be satisfactory.

Also, if anyone has technical documentation or schematics for the
Digitronics (or IOMEC?) 3500 paper tape readers, we would really

like to

obtain copies.

Thanks!
Eric Smith
PDP-1 Restoration Team

Send me your address and i will send you some Germanium PNP
transisors. Betas seem to increase with current on all of them.
Have some new "bullet" JAN 2N128; beta seems to be about 40 at 4mA
and max 6V operating. Can get lots of these.
Have mixed old small cylindrical can, TO-1 or TO-44 (1 ea):
*unmarked (?RCA) good to about 50V; beta near 100 at 2mA.
*RCA 2N384 good to about 60V; beta near 75 at 2mA.
*RCA 2N406 good to about 20V; beta near 100 at 2mA.
*RCA 2N2613 good to about 20V; beta near 200 at 2mA.
*? B175 good to about 50V; beta near 200 at 2mA.
*NTE158 good to about 20V; beta near 120 at 2mA (obviously these can

be

readily obtained).

*RCA TO-5 2N398 good to about 60V; beta near 100 at 2mA.


This was used as a neon lamp driver, and should be capable of a lot
higher voltage than 60V. Manual says 105V.

Of course nowadays a high voltage germanium looks pitiful and pathetic
compared to a silicon transistor.


*RCA TO-5 2N247 good to about 60V; beta near 100 at 2mA.

Anyway i will send these to you on an "all or none" basis.




Neon lamp driver?
Click to expand...
Darn; there was one GP germanium transistor that was made
specifically for high voltage and was rather common in those daze - now
i cannot remember the 2N number.
In any case for that application, you could safely use a silicon PNP
high voltage part as a replacement.
Will get the package out in the mail later today (Friday).
 
"Robert Baer" <robertbaer@earthlink.net> wrote in message
news:M6_be.465$HL2.257@newsread3.news.pas.earthlink.net...
Eric Smith wrote:
At the Computer History Museum (www.computerhistory.org), we're restoring
a DEC PDP-1 computer (www.pdp-1.org). In the process, we need to repair
....
Send me your address and i will send you some Germanium PNP transisors.
Betas seem to increase with current on all of them.
Click to expand...
Presumably you can use the address on the museum's web page.

I'm not involved with this project, but nonetheless I want to thank you for
doing your part to preserve history!
 
Eric Smith wrote:
---snip---
The PCB in your reader should be simple enough to chase it out
and
draw your own schematic if necessary That is what i had done).

We may do that at next week's team meeting. It's my understanding
that
we expect to desolder both the suspected bad GA004, and one that is
believed to be working properly, and look at both on a curve tracer.

Eric
Click to expand...
Hi Eric
When working on this old stuff, I've found that they tend
to use the same transistor in many different locations and under
different operating conditions. I've aften found that I can
swap transitors around and keep original parts. I just attach
a lable to let myself know what I've done in case it dies completely.
Also, one thing to look out for, other than leakage with
the germamium transistors is an increase in the DC resistance of
the emitter base connection. This usually shows on the emitter
side so it acts like a emitter resistor in circuit.
It shows clearly on a curve tracer.
Dwight
 
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