[vcf-midatlantic] Repair Workshop Wrap-up 3/30 & 3/31

Bill Dromgoole drummy at comcast.net
Thu Apr 4 13:01:11 EDT 2019


Univac Workshop Report


Duane and I arrived at the museum on Tuesday afternoon.
After getting settled at the on campus lodging, we started evaluating the condition of the Univac equipment.
The 1219B computer was working as usual with a small problem in the upper I/O channels.
The 1540 digital data recorder is in poor shape. Lower handler will not move at all.
No communication with 1219B computer. The 1532 I/O console appears to be working fine.

Duane built a USB to 1219B interface(MIL-STD 1397 type A) device using an arduino chip which he brought with him to test.
After playing around for a while we were able to upload files from a laptop computer to the Univac.
We spent most of the next day copying files to the computer and dumping them to the paper tape punch in the 1532 I/O console.
We also spent time trouble shooting the 1540 DDR concurrently with the file copying.

The first problem on the DDR turned out to be a bad logic translator card in the handler electronics itself.
Fortunately we were able to find one in the spares at the warehouse.
This corrected the signal to the pinch rollers but the tape kept jamming in the tape head area.
Turned out to be a bad roll of tape with poor oxide retention.

Over the next couple of days we found a lot of bad cards in the 1540 DDR with a lot of trips to the warehouse for parts.
Most of the failures were intermittent and took a while to locate.
At one time we were able to copy a program from memory to magnetic tape and then reload it to memory, although the handshaking was not proper.
Things kid of went downhill from there.
More card failures in the DDR. Not communicating with the 1219B, clocks not running bits in various registers always set, etc.
We were able to find most of these and get some of the communications back.
Meanwhile after editing some programs on the laptop and trying to punch new tapes the paper tape punch started to not work properly.
Next, the keyboard on the teletype started jamming and after that the paper tape reader stopped working.

Found that the tape reader power supply is failing. Plus and minus 15 volts slowly drifts down to 8 to 10 volts.
Was unable to repair before the weekend was over.
The keyboard is probably just not lubricated properly.
One of the new programs we copied uses the keyboard a lot.
We hardly used it before this trip. So that highlighted this problem.
The punch problem may be related to the reader power supply? Who knows.
Was able to use the time left after clean up on Sunday to scan another one of the Univac pubs to a PDF file for bit-savers.

Final status:
Computer working fine.
Digital data recorder is mostly working. Still needs possible alignments.
I/O console almost completely inop except for printer.



From: Jeffrey Brace via vcf-midatlantic
Sent: Sunday, March 31, 2019 4:08 PM
To: vcf-midatlantic
Cc: Jeffrey Brace
Subject: [vcf-midatlantic] Repair Workshop Wrap-up 3/30 & 3/31

We had about a dozen members working on their machines and VCF machines
Saturday and Sunday. Most did two days while some did one day.
Bill Dromgoole and Duana Craps had worked on the Univac 1219B in the museum
for the past week. They can give an update later as to their progress.
David Gesswein worked on the museum's PDP-8. He will send a report later.
There were others working on various projects.
I got there midday and wasn't able to work on anything Saturday.
Sunday I took VCF's turn at the InfoAge front desk.
Evan can fill you in on what he was working on as well as the others.

This time we went to a new place: MJ's for Saturday dinner. Everyone liked
it.
Afterwards we played Cards Against Humanity which is always a fun time.
Sunday morning we went to a new place: Mariner's Cove for breakfast. Also
great food!

The next workshop is April 13 & 14.

-- 
=========================================
Jeff Brace
Vice President
Vintage Computer Federation



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