23 May
2015
23 May
'15
5:59 p.m.
We spent Friday and Saturday debugging the PDP-12. We replaced a bad SN7400
driver chip and three bad bulbs in the front panel. We can now trust what
we see on the front panel for debugging information.
We tried some of the PDP-8 and LINC instructions and noticed that some of
the bits in the Instruction Register were stuck on. We swapped the two M216
(six flip-flops in three SN7474 ICs) flip-chips that make up the IR and the
stuck bits moved. We replaced the broken M216 with a spare, and now all of
the IR bits work correctly. With a working IR, we found that lots of the
PDP-8 instructions, and many of the LINC instructions now work. We can turn
the relays on and off and make noises through the speaker.
During other DEC restorations we have replaced LOTs of SN7474 ICs. We
pulled all of the M216 flip-chips and ran them in Warren's tester. We found
and replaced another bad M216, the one in slot E8 that controls the core
memory states. Now core memory works!
We went through the troubleshooting guide in Maintenance Volume-II. It has
a procedure for doing a quick test of core memory that revealed a problem
in the upper addresses. From looking at the prints it had to be one of two
G221 flip-chips. We swapped in a spare and found that the one in slot C09
was bad. Now all of the first 4k of memory works.
There is a problem with any PDP-8 instruction that has an address in the
lower 9 bits. All 12 bits of the instruction are used, so it makes a mess.
Debugging that issue will be the next project.
--
Michael Thompson
25 May
25 May
5:07 p.m.
Today we pulled all of the M113 flip-chips and tested them because SN7474
and SN7400 ICs seem to be a problem in these early DEC systems. The ones in
slots J33 and K30 were bad. Replacing them fixed the problem with the JMP
instruction. We did some more testing with the toggle-in programs and found
that ISZ cleared the AC. Replacing the M119 in slot H28 fixed that. All of
the toggle-in tests pass, so the processor is substantially functional.
Core memory in field 1 with addresses X5XX didn't work. We replaced the
G221 in slot D10 to fix that.
We tried the ASR33 Teletype that came with the system. The mechanics were
sticky from not being used for 30 years, but we got most of it free and
working. We could send characters to the Teletype, but could not receive
anything. The M706 receiver failed in the board tester. The spare is also
broken, so we need to fix both.
7:02 p.m.
On Mon, May 25, 2015 at 8:07 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
Today we pulled all of the M113 flip-chips and tested
them because SN7474
and SN7400 ICs seem to be a problem in these early DEC systems.
I have found from debugging a PDP-8/i and multiple PDP-8/L systems
that 80% of my failed ICs are SN7474 and SN7440 parts, and most of the
remaining 20% are SN7400. I think I've replaced 0-2 parts that
weren't one of those three.
Do you have any writeups on Warren's FLIP-CHIP tester? I made a
simple rig with a 1990s-era Ming IC tester and a 16-pin clip-lead
harness that can test each chip on a simple (M113, M117...) FLIP-CHIP,
but it can't test complex boards like the M220 or M706/M707.
Fortunately, most of the failures I've run into are a small handful of
TTL on the simple single-height boards, which this rig can catch.
I've been thinking about a smarter rig but haven't tried to build one.
-ethan
26 May
26 May
7:15 a.m.
On 26/05/2015 03:02, Ethan Dicks wrote:
On Mon, May 25, 2015 at 8:07 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
> Today we pulled all of the M113 flip-chips and tested them
Do you have any writeups on Warren's FLIP-CHIP
tester?
I'd be very interested too, especially since I'm about to try to
resurrect a PDP-8/L and then possibly another PDP-12.
--
Pete
Pete Turnbull
7:33 a.m.
I think many people would be interested. With an appropriate adapter,
his device could test modules from other manufacturers as well.
--
Will
On Tue, May 26, 2015 at 10:15 AM, Pete Turnbull
<pete at dunnington.plus.com> wrote:
On 26/05/2015 03:02, Ethan Dicks wrote:
On Mon, May 25, 2015 at 8:07 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
>
> Today we pulled all of the M113 flip-chips and tested them
Do you have any writeups on Warren's
FLIP-CHIP tester?
I'd be very interested too, especially since I'm about to try to resurrect a
PDP-8/L and then possibly another PDP-12.
--
Pete
Pete Turnbull 
5:23 a.m.
On Mon, May 25, 2015 at 08:07:04PM -0400, Michael Thompson wrote:
so the processor is substantially functional.
This is substantially cool.
We tried the ASR33 Teletype that came with the system.
The mechanics were
sticky from not being used for 30 years
This is substantially crazy :-)
IIRC the mechanics were kind of sticky when new.
The whole "changing flip-flops" thing really took me back. I learned
to do that in high school on our Control Data G-15. The multiply
instruction was the first to go :-)
I kept it running for some time using that method. (of course we did
not have a budget to order spares)
mcl
5:48 a.m.
"The M706 receiver failed in the board tester"
Do tell more about this mythical and very useful sounding board tester?
I'm looking at my racks and racks of logic, mostly M-series - 12, 16,
18, & 36 bit - and contemplating the debuggering with some dread...
Mike
On Tue, May 26, 2015 at 12:07 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
Today we pulled all of the M113 flip-chips and tested
them because SN7474
and SN7400 ICs seem to be a problem in these early DEC systems. The ones in
slots J33 and K30 were bad. Replacing them fixed the problem with the JMP
instruction. We did some more testing with the toggle-in programs and found
that ISZ cleared the AC. Replacing the M119 in slot H28 fixed that. All of
the toggle-in tests pass, so the processor is substantially functional.
Core memory in field 1 with addresses X5XX didn't work. We replaced the
G221 in slot D10 to fix that.
We tried the ASR33 Teletype that came with the system. The mechanics were
sticky from not being used for 30 years, but we got most of it free and
working. We could send characters to the Teletype, but could not receive
anything. The M706 receiver failed in the board tester. The spare is also
broken, so we need to fix both.
--
http://www.corestore.org
'No greater love hath a man than he lay down his life for his brother.
Not for millions, not for glory, not for fame.
For one person, in the dark, where no one will ever know or see.'
11:10 a.m.
From: Mike Ross: Tuesday, May 26, 2015 5:48 AM
Do tell more about this mythical and very useful
sounding board tester?
Warren's tester is similar in basic capability to the one that Henk and
I did some time ago, with some additional circuitry that's useful for
"load testing" -- telling the difference between an M6xx and an M1xx
card, etc.
Basically, ours had some I/O registers that you could set to control
I/O direction, and some latching transceivers to drive test vectors
to the module and read back results from the module. This was
done on a platform driven through a serial port talking to a 6802
microprocessor.
Warren's design, as mentioned by Michael, uses a set of SPI ports,
talking to 23S17 chips, which allow you to configure I/O direction,
set the test vector, and receive the result.
In addition, he's set up some LEDs and various loads and pull-ups,
which can be configured as needed to more accurately load the
module.
This all works quite well for "slow" testing of combinatorial logic.
It's more cumbersome to come up with test vectors for sequential
logic, though it can (usually) be done.
Level converters can be added for B/R/S series modules, though the
design of those while preserving the ability to set the I/O direction
is a bit of a pain (in terms of both cost and component count).
I think for more general testing (Gxxx?), it may be necessary to have
proper "pin drivers", somewhat like those used in PROM programmers.
For more dynamic testing, some me kind of local processing is
probably needed to judge the dynamic properties of a response,
and it may not be good enough to have to serialize and un-serialize
the data.
A shortage of gumption and relevant skills has kept me from being
helpful for a while now...
I'm looking at my racks and racks of logic, mostly
M-series - 12, 16,
18, & 36 bit - and contemplating the debuggering with some dread...
Mine are all 12 bit, but me too.
Vince
31 May
31 May
6:08 a.m.
We spent some time on the console Teletype that came with the PDP-12. The
platen was nearly impossible to move, so the Line Feed did not work. We
removed the platen, and found that the plastic in the bearing area had
swollen and was binding. We sanded, cleaned, and lubricate the bearing
surface and the platen now turns freely. On reassembly we found that none
of the Control Characters like Line Feed or Bell would work in Local Mode. We
fiddled for quite a while, but did not find a problem. We speculated that
something got bent when it could not move the binding platen.
We found a bad SN7474 E13 on the M706 Teletype Receiver flip-chip from the
PDP-12. We will repair and test it next week.
We borrowed the M706 Teletype receiver from the PDP-8/I and connected the
Teletype to the PDP-12. We loaded and ran a toggle-in program that echos
the keyboard to the printer. We were a little surprised when everything in
the Teletype worked OK. We were even more surprised when the Teletype now
worked correctly in local mode.
We borrowed the console cable from the PDP-8/I and connected my laptop to
the PDP-12. The terminal emulator worked correctly and echoed characters to
the PDP-12 and back.
We toggled in the RIM loader and then loaded the LBAA BIN loader from my
laptop. We ran the BIN loader and loaded and ran the PDP-8/I Instruction
Test #1. It actually works OK!
We tried twice to load MAINDEC-8I-D02B-D Instruction Test #2, but failed
both times. Running that diagnostic and others will be the project for next
week.
Al Kossow posted LOTS of PDP-12 manuals to Bitsavers. One manual includes
the allowable ripple for the power supplies. They allow 3,000mV of ripple
on the -30V supply for the core memory, so I guess that the 180mV that we
measured two weeks ago is OK.
On Mon, May 25, 2015 at 8:07 PM, Michael Thompson <
michael.99.thompson at gmail.com> wrote:
Today we pulled all of the M113 flip-chips and tested
them because SN7474
and SN7400 ICs seem to be a problem in these early DEC systems. The ones in
slots J33 and K30 were bad. Replacing them fixed the problem with the JMP
instruction. We did some more testing with the toggle-in programs and found
that ISZ cleared the AC. Replacing the M119 in slot H28 fixed that. All of
the toggle-in tests pass, so the processor is substantially functional.
Core memory in field 1 with addresses X5XX didn't work. We replaced the
G221 in slot D10 to fix that.
We tried the ASR33 Teletype that came with the system. The mechanics were
sticky from not being used for 30 years, but we got most of it free and
working. We could send characters to the Teletype, but could not receive
anything. The M706 receiver failed in the board tester. The spare is also
broken, so we need to fix both.
--
Michael Thompson
7:47 a.m.
Michael,
Sounds like you're making some real progress. Next time you're near the ASR33,
check the rubber hammer for the print cylinder. These have a tendency to self destruct and
in doing so, destroy the cylinder itself...and they can go at anytime. There's a
fellow on the Greenkeys that has tooled up and is producing replacements; same profile as
the original and easy to install. Cheap insurance, really. -C
On May 31, 2015, at 8:08 AM, Michael Thompson wrote:
We spent some time on the console Teletype that came
with the PDP-12. The
platen was nearly impossible to move, so the Line Feed did not work. We
removed the platen, and found that the plastic in the bearing area had
swollen and was binding. We sanded, cleaned, and lubricate the bearing
surface and the platen now turns freely. On reassembly we found that none
of the Control Characters like Line Feed or Bell would work in Local Mode. We
fiddled for quite a while, but did not find a problem. We speculated that
something got bent when it could not move the binding platen.
We found a bad SN7474 E13 on the M706 Teletype Receiver flip-chip from the
PDP-12. We will repair and test it next week.
We borrowed the M706 Teletype receiver from the PDP-8/I and connected the
Teletype to the PDP-12. We loaded and ran a toggle-in program that echos
the keyboard to the printer. We were a little surprised when everything in
the Teletype worked OK. We were even more surprised when the Teletype now
worked correctly in local mode.
We borrowed the console cable from the PDP-8/I and connected my laptop to
the PDP-12. The terminal emulator worked correctly and echoed characters to
the PDP-12 and back.
We toggled in the RIM loader and then loaded the LBAA BIN loader from my
laptop. We ran the BIN loader and loaded and ran the PDP-8/I Instruction
Test #1. It actually works OK!
We tried twice to load MAINDEC-8I-D02B-D Instruction Test #2, but failed
both times. Running that diagnostic and others will be the project for next
week.
Al Kossow posted LOTS of PDP-12 manuals to Bitsavers. One manual includes
the allowable ripple for the power supplies. They allow 3,000mV of ripple
on the -30V supply for the core memory, so I guess that the 180mV that we
measured two weeks ago is OK.
On Mon, May 25, 2015 at 8:07 PM, Michael Thompson <
michael.99.thompson at gmail.com> wrote:
Today we pulled all of the M113 flip-chips and
tested them because SN7474
and SN7400 ICs seem to be a problem in these early DEC systems. The ones in
slots J33 and K30 were bad. Replacing them fixed the problem with the JMP
instruction. We did some more testing with the toggle-in programs and found
that ISZ cleared the AC. Replacing the M119 in slot H28 fixed that. All of
the toggle-in tests pass, so the processor is substantially functional.
Core memory in field 1 with addresses X5XX didn't work. We replaced the
G221 in slot D10 to fix that.
We tried the ASR33 Teletype that came with the system. The mechanics were
sticky from not being used for 30 years, but we got most of it free and
working. We could send characters to the Teletype, but could not receive
anything. The M706 receiver failed in the board tester. The spare is also
broken, so we need to fix both.
--
Michael Thompson 
1 Jun
1 Jun
1:33 a.m.
Yes, the new rubber hammers are available from David Tumey. I think he wants
about $7 for 10 of them. I have a supply of them here in the UK for anyone
that needs any.
Regards
Rob
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Cory
Heisterkamp
Sent: 31 May 2015 15:48
To: General Discussion: On-Topic Posts
Subject: Re: PDP-12 Restoration at the RICM
Michael,
Sounds like you're making some real progress. Next time you're near the
ASR33, check the rubber hammer for the print cylinder. These have a
tendency
to self destruct and in doing so, destroy the cylinder
itself...and they
can go at
anytime. There's a fellow on the Greenkeys that
has tooled up and is
producing
replacements; same profile as the original and easy to
install. Cheap
insurance,
really. -C
On May 31, 2015, at 8:08 AM, Michael Thompson wrote:
> We spent some time on the console Teletype that came with the PDP-12.
> The platen was nearly impossible to move, so the Line Feed did not
> work. We removed the platen, and found that the plastic in the bearing
> area had swollen and was binding. We sanded, cleaned, and lubricate
> the bearing surface and the platen now turns freely. On reassembly we
> found that none of the Control Characters like Line Feed or Bell would
> work in Local Mode. We fiddled for quite a while, but did not find a
> problem. We speculated that something got bent when it could not move
the
binding platen.
>
> We found a bad SN7474 E13 on the M706 Teletype Receiver flip-chip from
> the PDP-12. We will repair and test it next week.
>
> We borrowed the M706 Teletype receiver from the PDP-8/I and connected
> the Teletype to the PDP-12. We loaded and ran a toggle-in program that
> echos the keyboard to the printer. We were a little surprised when
> everything in the Teletype worked OK. We were even more surprised when
> the Teletype now worked correctly in local mode.
>
> We borrowed the console cable from the PDP-8/I and connected my laptop
> to the PDP-12. The terminal emulator worked correctly and echoed
> characters to the PDP-12 and back.
>
> We toggled in the RIM loader and then loaded the LBAA BIN loader from
> my laptop. We ran the BIN loader and loaded and ran the PDP-8/I
> Instruction Test #1. It actually works OK!
>
> We tried twice to load MAINDEC-8I-D02B-D Instruction Test #2, but
> failed both times. Running that diagnostic and others will be the
> project for next week.
>
> Al Kossow posted LOTS of PDP-12 manuals to Bitsavers. One manual
> includes the allowable ripple for the power supplies. They allow
> 3,000mV of ripple on the -30V supply for the core memory, so I guess
> that the 180mV that we measured two weeks ago is OK.
>
> On Mon, May 25, 2015 at 8:07 PM, Michael Thompson <
> michael.99.thompson at gmail.com> wrote:
>
>> Today we pulled all of the M113 flip-chips and tested them because
>> SN7474 and SN7400 ICs seem to be a problem in these early DEC
>> systems. The ones in slots J33 and K30 were bad. Replacing them fixed
>> the problem with the JMP instruction. We did some more testing with
>> the toggle-in programs and found that ISZ cleared the AC. Replacing
>> the M119 in slot H28 fixed that. All of the toggle-in tests pass, so
the
processor is substantially functional.
>>
>> Core memory in field 1 with addresses X5XX didn't work. We replaced
>> the
>> G221 in slot D10 to fix that.
>>
>> We tried the ASR33 Teletype that came with the system. The mechanics
>> were sticky from not being used for 30 years, but we got most of it
>> free and working. We could send characters to the Teletype, but could
>> not receive anything. The M706 receiver failed in the board tester.
>> The spare is also broken, so we need to fix both.
>>
>
>
>
> --
> Michael Thompson
3263
days inactive
3271
days old
10 comments
9 participants
participants (9)
-
coryheisterkamp＠gmail.com -
ethan.dicks＠gmail.com -
linimon＠lonesome.com -
michael.99.thompson＠gmail.com -
pete＠dunnington.plus.com -
robert.jarratt＠ntlworld.com -
tmfdmike＠gmail.com -
v.slyngstad＠frontier.com -
wdonzelli＠gmail.com