IBM 1130 Restoration at TNMOC in 2017

14th January 2017

• Finally got around to looking at the console printer.
  • Replaced the tab pivot mechanism with a metal after-market version which should last for a long time.
  • After a lot of trail and error and several attempts, I finally worked out how to fit the new rotate tape.
  • Tested the printer and it works pretty well, with a few misaligned characters (nothing new). Will need to run it for a while to loosen it up again
• Gave the line printer a quick test and it is still printing without a ribbon, but it is a lot fainter
• Unable to find a replacement plastic tilt cam. Will see if I can repair/strengthen existing cam plastic parts. I have some others cams from a Selectric typewriter but the plastic has also split on them.

18th February 2017

• Spent most of the day looking at the 029 punch, especially why it does not feed cards from the hopper.
• After cleaning and adjusting the picker knives used to drag a single card from the hopper through to the first station, it is much more reliable at feeding cards, although it can still be difficult. This is is because the picker knives are well worn so it does not pick up the whole of the card at the top.
• I also cleaned out and lubricated the punch area and ensured card feeding, especially at the end was working well.

6th May 2017

• I was warming up the card reader prior to loading the printer test card set when the system suddenly powered itself off. It had never done this before so I was surprised. I attempted to power it up again but nothing happened.
• I disconnected everything and started checking the fuses, which all tested OK. I then noticed one of the +3V voltage regulator unit breaker had tripped. I reset it and powered the system on again but a few seconds later it tripped again. Repeated attempts did the same thing.
• I then noticed the Selectric had locked up. I freed it but the power off still occurred when I powered it on again.
• I then isolated the card reader, selectric console and line printer by unplugging their cables from the main processor cabinet but this also made no difference.
• It was always the same +3V regulator unit that tripped so I swapped the crowbar card and regulator card between it and the -3V regulator unit but the fault stayed with the +3V regulator unit.
• So we either have a short on the +3V rail causing the regulator to trip or we have a faulty regulator unit. I do have a spare +3V regulator unit which was from the old 1130 the museum once had, but I don't know its condition. It also looks different so I will need to check it before trying it in the system.

27th May 2017

• Did further investigation of the tripping +3V regulator unit. The +3 and -3 regulator units are actually the same unit, just the external unregulated supply is either +6.6 or -6.6 Volts and the external wiring is slightly different to yield the necessary + / - voltages.
• I swapped the 2 units over and the fault stayed with the same physical unit, so the fault is probably within the regulator itself and not a short on the +3v rail.
• I removed the +3V regulator unit, disconnected and checked the 11000uF 10V capacitor which was across the input lines. This failed an ESR test (>40 Ohms and only measuring 2.7uF). It had clearly gone bad and may be the cause of the problem.
• I then did the same test on the same sized capacitor in the -3V regulator and that tested OK (ESR 0.04 Ohms, 13560uF).
• I then tested the 11000uF 10V capacitor in the spare +3V regulator. This also tested OK (ESR 0.02, 13260uF), even though it has probably not been used for over 30 years!
• Trawling the net for a suitable replacement it soon became clear I would not find a similar capacitor of the same physical size, capacitance and voltage. The closest was the right height and diameter but was 10000uF @ 63V. It needed to be the same size as it was secured by 2 holding rods that were screwed into the baseplate rather than a capacitor holding cup, the physical space does not allow anything fatter and the wiring any shorter.
• I then had 2 choices, try out the replacement regulator or swap over the capacitor. Due to its age I needed to reform it anyway so decided to try swapping it first.

29th May 2017

• The spare capacitor was successfully reformed over the previous 24 hours and fitted into the tripping +3V regulator unit.
• During the day I also started to reform the capacitor in the -3V regulator. This showed good voltage drop across the resister in-line with the DC supply, but once the voltage increased above the nominal 6.6V operating voltage of regulator it was clear it needed longer than I had during the day to complete the process. I left it reforming at the capacitors 10V level for several hours and near the end of the day I re-fitted both regulator units and powered on the 1130. The power remained on without tripping and did so for 45 minutes before the museum closed.
• So, the faulty capacitor was the cause of the tripping. I now need to look for a best fit replacement capacitor.
• The next step is to reconnect everything again and test it at full load. Once that is proven I will take out the -3V regulator unit and complete the capacitor reforming to extend its working life. Given the state of this capacitor, and that one has already failed, I will also reform the capacitor in the +6V regulator unit.

24th June 2017

• I managed to find a direct replacement for the 11000uf 10V capacitor on ebay US and they arrived during the week. I bought 5 and they all check out OK.
• The +6V regulator supply also uses a 11000uf 10V capacitor. This appeared to be OK when it was initially reformed but showed signs of going bad nearer the 10V limit. To pre-empt a possible failure I replaced it with one from ebay.
• I reconnected the 1442, 1132 and console printer to the 1130, refitted the 3 regulator supplies and the system was powered up. It was left running for the next hour without any problems. On checking the regulated outputs I measured +3.2, -3.05 and +6.2 which were good.
• To check the system had not been affected by the failed +3V supply, I loaded the CPU tests card deck, but multiple read attempts kept failing with a READ REG error. I cleaned all the path ways and optics but still saw READ REG errors, with the errors occuring at different places in the card deck. Taking out sections of cards around the read failure and loading them often read perfectly so I appear to have an intermittent read error.
• I remembered I was getting more frequent read errors just before the +3V regulator failed. I also remember we had similar intermittent read errors when we were first trying to read cards several years ago. One thing that did seem to affect things was the light brightness. Also the lamp for the optics is always on whenever there is power to the card reader so its brightness may have degraded as the lamp got older causing mis-reads. There is a light adjustment pot underneath the rear of the unit so I adjusted it slightly higher and was able to read cards reliably again.
• The system is now fully working again.