Subject: PDP-8/M/F front panel
From: Douglas W. Jones <[email-masked]>
To: [email-masked]
Date: Tue, 19 Jan 93 15:29:54 CST

Date: Tue, 19 Jan 93 15:29:54 CST
From: Douglas W. Jones <[email-masked]>
To: [email-masked]
Subject:  PDP-8/M/F front panel

I've just gotten down to work debugging the front panel on my
second hand PDP-8/F.  3 of the LED's won't go out (and one more
won't go on) in the data row.  The problem is in the 74L54 chips
that are used to multiplex the data for the data lights.  I can't
get 74L54 chips, but I can get 74LS54 chips, these have the right
pinout, and more importantly, three of the 74L54 chips have
already been replaced with 74LS54 chips.

So, I verified that the problem is indeed in those chips by
replacing one, and now I have to wait for 3 more (since I bought
the last one in stock from the electronics place near my office.

But, my question is, what is the problem with the 74L54 chips in
the 8/F front panel?  I'm replacing 4, and three others have been
replaced some time ago.  Did DEC screw up when they selected this
chip?  Is there something dangerous about the way it is driven
that tends to burn it up?

By way of information, the symptom I'm getting is an output that
goes from 2.5 to 4.5 volts as the inputs change, instead of 0.3
to 4.5 volts (more normal).  This suggests a blown output
transistor, as if the chip tried to sink too much current at some
time (difficult to do, considering that it only drives a 7404
chip).

A second question is, does anyone know of a source of 74L54 chips?
The 74LS54 seems to work, but it would be nice to use the right
part if I could get one.  The 74LS54 loads its inputs just slightly
more than the 74L54, and one of the inputs is the DATA bus, so this
could matter in a fully configured system.  Any experience or
warnings about this would be appreciated.

                                Doug Jones
                                [email-masked]

From: [email-masked] (Robert Smith)
Subject: Re: PDP-8/M/F front panel (fwd) reply
To: [email-masked]
Date: Tue, 19 Jan 93 21:42:05 EST

From: [email-masked] (Robert Smith)
Subject: Re: PDP-8/M/F front panel (fwd) reply
To: [email-masked]
Date: Tue, 19 Jan 93 21:42:05 EST
X-Mailer: ELM [version 2.3 PL11]

Forwarded message:
From rmsmith Tue Jan 19 21:40:27 1993
From: rmsmith (Robert Smith)
Message-Id: <[email-masked]>
Subject: Re: PDP-8/M/F front panel
To: [email-masked] (Douglas W. Jones)
Date: Tue, 19 Jan 93 21:40:09 EST
In-Reply-To: <[email-masked]>; from "Douglas W. Jones" at Jan 19, 93 3:29 pm
X-Mailer: ELM [version 2.3 PL11]

Doug,
Back in the days of the omnibus, Louie Klotz (mostly) and
Remo Vogelsang changed the timing on me a couple of times.

The loads on the bus, with the PROGRAMMER'S CONSOLE installed
were a concern cause of guys like me designing i/o devices.
The LED console, I don't remember who redesigned it from the
lamps, was intended to be more reliable and produce less loads
on fully loaded 8/e systems....we thought a big system was a
two box four omnibus system.....that is two 8/e boxes.

If you are not fully loading the omnibus, and you are not
running one of the prototype kk8/e processors, with all the
green wires like univ of colorado had on the mariner project,
it won't effect your system.

Someone might say it is not a pure system, but you can counter
that with the fact that you can't find the date codes.

Only a few chips were critical in the system if I remember correctly.
On the EAE and I think there was one other peripheral.....
hope this helps....bob

To: "Douglas W. Jones" <[email-masked]>
Cc: [email-masked], [email-masked]
Subject: Module locations and power up hints
Date: Wed, 27 Jan 93 11:39:53 -0800
From: [email-masked]

To: "Douglas W. Jones" <[email-masked]>
Cc: [email-masked], [email-masked]
Subject: Module locations and power up hints
In-Reply-To: Your message of "Mon, 25 Jan 93 13:40:06 CST."
             <[email-masked]> 
Date: Wed, 27 Jan 93 11:39:53 -0800
From: [email-masked]

> You have a PDP-8?  The original kind?  Would you do me a favor and see
> if there are any differences between the module maps in the maintenance
> manuals I sent and the module layout in your -8.  We have a few differences,
> and before I turn it on, I want to know if they're misplaced boards or if
> they're normal.
> 				Doug Jones
> 				[email-masked]

There are no interesting differences between the module layout in the
maintenance manual and my PDP-8. One dual flip-flop module in the memory is
blue instead of red, but its in the right place. Several modules shown as R in
the manual are S in my machine, most often S111 instead of R111.

My machine has a fairly low serial number, maybe around 250. The real serial
number plate is missing, but some of the chassis plates are around that, and
the core box is emi s/n 96.

It has no options whatsoever. Not even data break. So of course I couldn't
check positions of any modules which are in options.

Since your machine's serial number is apparently 85, I would expect it to
match the module locations fairly well. I would be careful about moving
anything. Maybe you should spot check signal wiring in the
suspect slots before deciding what to do.

If you haven't powered it up yet, and its been in storage for many years, you
might want to bring the voltages up slowly to give the power supply caps a
chance to reform. This is more of an issue with high voltage electrolytics,
but I have heard of flakey low voltage supplies that were powered up
quickly. I did this with my PDP-8 the first time and have had no trouble with
the power supply. I've recently done some testing on old high voltage caps,
and recommend this sequence: Find a large enough variable transformer, and
plug the computer into it. Turn the power all the way down and turn on the
computer. Bring the voltage up slowly (I take up to half an hour, but that
might be too conservative) to half voltage. Let it sit at half voltage for up
to 24 hours (this is not particularly conservative - by my measurements, it
takes many hours for the leakage current to drop.) Check the power supply for
hot parts and turn it off if anything heats up too much. If its all OK, turn
the power up slowly to full voltage. Check again for hot parts in the power
supply. Also check around the memory. Reset the computer by pressing Start
with Halt down, since the slow power up will confuse any power on reset
circuit it might have. Enjoy!

I think its probably OK for the processor to have half voltage on it, but if you
are nervous about that disconnect the DC voltages from the power supply to the
processor before doing the above. This also lets you use a smaller variable
transformer. As far as I know, there aren't any critical electrolytics in the
processor, you only have to form up the ones in the power supply. Be aware
that some power supplies (especially switchers) don't like this treatment, but
I think the PDP-8 supply is linear and will do fine.

Have fun -

Paul

Date: Wed, 27 Jan 1993 13:29:03 -0800 (PST)
From: Mark Crispin <[email-masked]>
Sender: Mark Crispin <[email-masked]>
Subject: help in reviving a PDP-8
To: [email-masked]

Date: Wed, 27 Jan 1993 13:29:03 -0800 (PST)
From: Mark Crispin <[email-masked]>
Sender: Mark Crispin <[email-masked]>
Subject: help in reviving a PDP-8
To: [email-masked]
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

I have a PDP-8/e and PDP-8/f, neither of which are working.  The 8/e never
worked from the time I got it from salvage, and its main purpose in life has
been to provide spare parts for the 8/f.

The 8/f became cranky a couple of years ago when it would not run Focal
properly; I have good reason to believe that the problem was in the TTY
board's interrupt handling.  Now, however, it isn't able to access memory at
all; I just get zeros from any memory I read.

I've already done all the obvious things (I was an 8 software hacker in the
mid 1970's...).  It's clear that the machine needs some hardware debugging,
and it's beyond my expertise to do so (not to mention having other far higher
projects to do).  It's probably just a matter of a couple of chips from Radio
Shack...

Are there any competant 8 hardware hackers in the Seattle area who would like
to take a look at it?  Anyone who revives my little 8/f is welcome to spare
parts from the 8/e (including the 8/e chassis).

Oh.  I didn't mention.  The 8/e has a TU56.  I would dearly love to get an
OS/8 DECtape system going.  I have no idea whether or not the TU56 works; nor
whether any of the DECtapes I have are still readable.  I *am* willing to
throw money into this effort.

Date: Wed, 27 Jan 93 15:50:20 CST
From: Douglas W. Jones <[email-masked]>
To: [email-masked]
Subject: mysterious box.

Date: Wed, 27 Jan 93 15:50:20 CST
From: Douglas W. Jones <[email-masked]>
To: [email-masked]
Subject: mysterious box.

A friend has been trying to get my help, by E-mail, in identifying a very
dirty and very unloved DEC rack he found in a cluttered and dark basement

Here's the current breakdown we've arrived at for the system configuration:
         _______
>       |_______|
>       | Tape1 | < TU55 \
>       | _____ |         > serial numbers 2014 and 2078
>       | Tape2 | < TU55 /  missing some logic modules?
>       | _____ |
>       | empty |
>       | _____ |
>       |  CPU  | < Perhaps a PDP-8/S, but with no lights and switches
>       | _____ |   just black panel with keyswitch in left corner.
>       | power |   The machine seems to be made of S, R and G series logic.
>       | _____ |
>       | logic | < M series logic on the front of the rack, S, R and G
>       |_______|   series logic on the back of the rack.  Tape controller?
>       ||_____||

The key to the CPU type is that it has a backplane on top, with lots of
red and green (by the light of a flashlight, so they could as well be
blue) handles on the circuit boards as seen from below.  It may not be
a CPU for all we know at this point.  The DIGITAL id plate on the back
says BA08A/141, if someone can figure this out.

The name "Astrotype" seems to be somewhere on or above the tape drives,
suggesting that this may once have been an OEM'd system for some dedicated
application, perhaps typesetting.  Any ideas what we're dealing with?

					Doug Jones
					[email-masked]

From: Sarr Blumson <[email-masked]>
To: "Douglas W. Jones" <[email-masked]>
Cc: [email-masked]
Date: Thu, 28 Jan 93 09:20:09 -0500
Subject: Re: mysterious box. 

From: Sarr Blumson <[email-masked]>
To: "Douglas W. Jones" <[email-masked]>
Cc: [email-masked]
Date: Thu, 28 Jan 93 09:20:09 -0500
Subject: Re: mysterious box. 
In-Reply-To: Your message of Wed, 27 Jan 93 15:50:20 CST .
             <[email-masked]> 

     The key to the CPU type is that it has a backplane on top, with lots of
     red and green (by the light of a flashlight, so they could as well be
     blue) handles on the circuit boards as seen from below.  It may not be
     a CPU for all we know at this point.  The DIGITAL id plate on the back
     says BA08A/141, if someone can figure this out.

I haven't even _seen_ a PDP-8 in almost 20 years, but isn't a BA09 a line
printer controller?

--------
Sarr Blumson                         [email-masked]
voice: +1 313 764 0253               FAX: +1 313 763 4434
CITI/IFS, University of Michigan, 519 W William, Ann Arbor, MI 48103-4943

Date: Thu, 28 Jan 93 11:24:03 CST
From: Douglas W. Jones <[email-masked]>
To: [email-masked]
Subject: Help identify box, part II

Date: Thu, 28 Jan 93 11:24:03 CST
From: Douglas W. Jones <[email-masked]>
To: [email-masked]
Subject: Help identify box, part II

At this point, here's what we know we've found, covered with dust and
long disused in a dark basement:
        _______
       |_______|
       | Tape1 | < TU55 \
       | _____ |         > serial numbers 2014 and 2078
       | Tape2 | < TU55 /  missing some logic modules?
       | _____ |
       | empty |
       | _____ |
       | BA08A | < This is an expansion box for the PDP-8/L.
       | _____ |   We don't know if it has 4K of core in it or not.
       | power |
       | _____ |   
       | logic | < On the front of the rack is a BE01, behind it is a
       |_______|   still unidentified collection of Flip Chips.
       ||_____||

So, what's a BE01?  My friend has E-mailed me a module map for the BE01,
in the hope that this would help pin it down.  Working by poor light
through dust, there may be some incorrect numbers here, particularly,
some M203's might be M023's or the opposite.

		 The cables up here go
                 to the unidentified
		 logic at the back of
		 the cabinet.

R                c c c c c c c c c c c M M M M M M M M
O                a a a a a a a a a a a 6 6 6 6 6 6 6 9
W                b b b b b b b b b b b 5 5 5 5 5 5 5 0
1                l l l l l l l l l l l 0 0 0 0 0 0 0 7
                 e e e e e e e e e e e 

R                  M M M M M M M M M M M M M M M M M M e e c c c c  These
O                  5 5 5 5 5 5 5 5 6 6 6 6 6 6 6 6 9 1 m m a a a a  cables
W                  0 0 0 0 0 0 0 0 5 5 5 5 5 5 5 5 0 0 p p b b b b  connect
2                  7 7 7 7 7 7 7 7 0 0 0 0 0 0 0 0 7 1 t t l l l l  from
                                                       y y e e e e  row 2
                                                                    to
R  w S S S M M M e C M M M M M M e M M M M M M M M M M M e c c c c  row 3,
O  h 0 0 0 5 1 2 m 3 1 1 1 2 2 0 m 1 1 1 1 2 2 2 6 6 6 6 m a a a a  there
W  i 4 4 4 0 1 0 p 2 1 6 0 0 0 6 p 1 1 1 1 0 0 0 2 2 1 1 p b b b b  may be
3  t 0 0 0 1 3 3 t 0 1 1 1 3 3 2 t 7 3 3 3 1 1 3 3 3 7 7 t l l l l  more
   e             y               y                       y e e e e  of them.

R  e c S w M M M e C M M M M M M e M M M M M M M M M M M 
O  m a 0 h 5 1 2 m 3 1 1 1 2 2 0 m 1 1 1 1 2 2 2 6 9 1 1
W  p b 4 i 0 1 0 p 2 1 6 0 0 0 6 p 1 1 1 1 0 0 0 2 0 1 1
4  t l 0 t 1 3 3 t 0 1 1 1 3 3 2 t 7 3 3 3 1 1 3 3 7 7 3
   y e   e       y               y

     ^
     | This cable is a thick cable, I don't know where it goes.

All rows above are read from the handle sides of the boards.
The cards labelled "S040" have no puller.

There's no identification on the back of the chasis, where the cables from
the first row connect.  The back appears to have 4 1/2 rows, and most of
the cables connect to the top half-row.

					Doug Jones
					[email-masked]

Date: Thu, 28 Jan 93 18:43 GMT
From: PJHurst <[email-masked]>
To: pdp8-list <[email-masked]>
To: pdp8-list <[email-masked]>
Subject: strange box

Date: Thu, 28 Jan 93 18:43 GMT
From: PJHurst <[email-masked]>
To: pdp8-list <[email-masked]>
To: pdp8-list <[email-masked]>
Subject: strange box

If it was not for the serial number plate and r-series mods in the box
i would say that you have a typeset-8 configuration with a 8/L CPU. Doug
See if there are any serial number plates on the logic racks in the bottom
of the box. Also is this mysterious rack, a old or new sytle cab? That is
is the rack the old BUD tubular rack with treaded inserts to hold the logic
(early 60's-late 60's use by DEC) or the newer type racks that dec used until
a few years ago?

Paul Hurst
Salt-Ash Systems
Chester, VT