Wednesday, September 2, 2015

Diving into the console printer inability to trigger tab by program command, plus work on SAC interface box enhancement


I now suspect that the tab interposer spring which should be pulling it strongly back to activate a cycle is an incorrect type. It is far too weak and thus the interposer won't slide back when pulled down by the pull link from the operational magnet.

There is also an adjustment screw which is the pivot for the interposer. On the tab interposer, this screw is much higher than the other four interposers. This may be contributing to the problem. Unfortunately, the direct way to get to these adjustments will involve removing the operational magnet assembly, a major pain.

Operational Magnet assembly removed, pull link clevises are black
Access to underside of interposers with op magnet removed
I bit the bullet and removed it. I did verify that a weak spring is the root problem and detached one end of the spring, but the far end is buried.

Correct interposer springs shown, under tension

Tab spring with almost zero tension to pull interposer rear-ward
I do hope that I don't also have to remove the mainspring, forward and reverse nylon cords, various mechanisms and starter capacitor so that I can also get to the rear of these mechanisms. That would be another huge PITA. I will hope I can do the equivalent of arthroscopic surgery with all this in the way.

Mainspring to right, other stuff blocking rear mount of tab interposer spring

I worked on my reset and startup logic for the emulation engine - the circuit that will fire off the four relays to "push" the Imm Stop, Reset and Prog Start buttons. NB - Prog Start is a DPDT switch and thus needs a pair of my SPDT relays.

Relays to push the three buttons on the 1130 console
Once I cleaned up the circuit with good noise filtering, it was working just as I wished. I wired up the relay board and was happy with the speed of the button pushing and the duration - I might not need to lengthen this beyond the 0.1s clock pulses.

Emulation engine that drives the relays with fixed timing
Here is a quick video of it sequencing, the tiny LEDs on the relay panel light as each of the buttons is "pushed". Once I work out the mounting method to install these two boards under the keyboard panel, I will wire in the switches to the relays.

I bought twisted pair cables, very similar to those used in the I/O cables on the 1130, in order to make up the supplemental cable for my SAC Interface Box. This cable will carry five signals, two inbound and three outbound. The signals involved are:

  • Inbound state of Interrupt Level 0
  • Inbound state of Interrupt Level 1
  • Outbound request to trigger Interrupt Level 0
  • Outbound request to trigger Interrupt Level 1
  • Outbound request to trigger emulation engine
I cut the twisted pairs to length and am now waiting for heat shrink tubing to arrive so I can turn this into a proper cable rather than several loose twisted pairs. It is the same length as the main SAC cable, plus 3 feet for runs inside the 1131. I haven't chosen a connector mechanism yet. 

No comments:

Post a Comment