return to main pageContinuing Maintenance
Table of Contents
- Introduction
- "Up-Time" improvements
- Storage of Tools & Parts
- Various Adventures
- Status of the 1401 Demo Lab" series
Two tasks have been started to improve "up-time".
- Aided Circuit Card Testing
- Aided Relay Testing
I'm using the word "Aided" to help avoid unrealistic expectations.
Actually, Grant Saviers started designing and drumming up support for an SMS card tester system since about Spring 2005 when we finally got adequate 50 Hz power. Support was slow in coming. So Grant continued designing with little moral support. Likely he figured that good, but not perfect, was better than nothing at all -
- - cards were being adequately repaired by Tim Coslett
- - many people (especially Ed Thelen - me - ) remembered many cards being shipped to sites as "repaired" or "no problem found" that were defective. These people wished a "perfect" card tester, including verifying voltage tolerances, ability to drive rated loads, perform at rated speed, functional temperature range and maybe even vibration sensitivity.
Then Tim Coslett moved to Montana, and Jim Hunt took over fixing SMS cards.
Then Jim got a day job and was not available.So, in 2014 George Ahern linked up with Grant Saviers and started fabricating Grant's designs.
See Towards Fixing SMS
The previous single work and demo room have been superceeded by Various Adventures
- Ken - Tape Drive Intermittent Aug 14, 2019
- Ken - Card Reader Clutch Sept 25, 2019
- Ken - Card Reader Clutch Sep 18, 2019
- Ken - Card Reader Clutch Aug 7, 2019
- Ken - Card Reader Clutch Sept 25, 2019
Ken - Tape Drive Intermittent Aug 14, 2019
Subject: (Unofficial) report on Wednesday's restoration
From: Ken Shirriff
Date: Wed, Aug 14, 2019 6:07 pm
The tape drives on DE had an intermittent problem when running the exerciser test. Michael was looking into it and can provide more details. I scoped the signals from the tape drive and found that the C bit signal from tape drive on the left looked very bad, but all the rest of the bits from all the tape drives were fine. Yellow is the bad signal below: ![]()
As far as we can tell, this is unrelated to the exerciser error. But this should probably be investigated. Maybe a bad preamp card in the tape drive? I ran out of time to investigate.The second problem turned up just before I left. The CT card reader partially fed one card, went into reader stop, and wouldn't do a NPRO. Turning the computer off and on cleared the reader stop, but it came back after trying NPRO again. It seems pretty unusual for NPRO to not work at all.
Ken
Ken - Card Reader Clutch Sept 25, 2019
Subject: Re: Notes on 1402 card reader clutch problem
From: Ken Shirriff
Date: Wed, September 25, 2019 8:37 pm
Another update on the CT card reader problems. Today we had different symptoms. First, Carl ran powers-of-2 and the card reader operated perfectly. I attached an oscilloscope probe (carefully) to see the brush timing, and then the card reader started malfunctioning. Each time I tried to load, a card would move to the first position (halfway out of the hopper) and then hit a Reader Check. I.e. before it had reached any brushes. I had to hit Check Reset on the 1401 a couple of times to clear the fault, which was strange. This problem happened many times and we couldn't make it go away, even with power-cycling. Carl looked at some relays, but I'll let him describe what he found.
Then, the problem suddenly reverted to the original intermittent problem, where the card reader would fail to clutch at all and no cards would move. This problem persisted until we had to leave because of the demo.
Details on the clutch problem: I started scoping INLK STOP (C12 36.02.11.2), continuing from last week. Last time, it seemed that INLK STOP wasn't getting cleared by the reset key, but this time it did. There's a pulse from the Load key (pin F), clearing output P. So this seems to rule out the INLK STOP theory from last week.
![]()
We moved on to READ FEED (36.10.11.2) and confirmed that it's getting INLK STOP correctly. We started to look at the PROC FEED signal (pin A) which provides the pulses to the READ FEED trigger. These seemed to be missing, which would cause the problem. We also looked at the PROC FEED signal output from the integrator (C08 pin F) and that seemed stuck too. So our current hypothesis is the PROC FEED signal from the 1402 is not correct.
The CE Manual has a good discussion of the various relays and their sequences, starting at page 4-1. In particular, PROC FEED depends on relays RC5, R7-2T, R6-3N, R11-3N and R11-2N, so that path would be worth checking.
For some background, here's my blog post from a year ago when the DE 1402 had Reader Check on NPRO, due to a bad relay #4. (The current problem appears unrelated, but my blog post discusses some Reader Check circuitry.)
Ken
Page start July 7, 2014
Updated Oct 11, 2019