Thursday, September 17, 2015

Progress on 1053, keyboard and SAC Interface box, albeit measurable in microinches not normal strides


With the diagnostics back in the machine and running, I put the machine through its paces. I found that the carrier return interposer would sometimes fail to relatch - the same goop that was impacting the relatch of the index interposer yesterday. Many of these things work out okay with repeated operation of the mechanism.

Most operations and all the typeball characters were working well, but I had some challenges with the diagnostic program - I am still not fully in control of how to work its many options - so I am not positive yet. The sections of tests it printed seemed to be okay, but between extra skipping with the CR issue and shaky control over the diagnostics, not everything was working. It seemed that some sequences of typing were ending prematurely, as if spurious signals were confusing the IO adapter.

When I got back out at the end of my lunch hour, I fired it up to set it to specific routines - one tests with tab and CR sequences, another tests with backspace and index sequences, the registration test will type O and * using space and backspace so that each location should have the same circle with a star inside. It would identify any failure to smoothly space and backspace.

Alas, somehow the machine won't honor the Load IAR button, so I can't start the machine at the appropriate location even though core is properly loaded. This problem cropped up out of the blue. Until I sort out what is wrong with the 1131, no point trying to run diagnostics to work on the 1053 or keyboard.

I was able to load into location 0 and 1 a branch to the starting address 0220 and run the diagnostic. The load IAR button works when the B register contents are non-zero, although it forces the IAR to the B reg contents plus bit 5 for some reason. I suspect a hot bit from the interface box, since the console printer is typing some but not all characters it should. That is, it sits idle then resumes with another portion of the string, almost as if something is stepping on its operation.

I confirmed that the index operation (line feed without carrier return) is working under program control. Hopefully I will get a full thumbs up from the diagnostics when I clear up my basic machine problems.


Crawled back under and inside the 1131 to continue fighting the wiring at the resistor panel - one pin to insert in the panel and one vampire tap to repair. Sounds simple, but extremely limited and awkward access make this harder than it would seem.

By lunchtime I had things sorted out down under and working properly - although I still had to test the virtual Program Load to make sure all connections are right. I was able to load core memory and run things in the machine, which was good enough for now.

Later in the afternoon, I went out and ran through the virtual Prog Load function a few times - it works just fine. Once I can figure out what is plaguing the system, stopping Load IAR from the console bit switches and probably interfering with the typewriter data flow, I can continue.

I happened to put a VOM on the VCC pins of the driver chips and found one of the two boards at 3.3V - not 5V as they both should be. These are 74LS06N chips and should have the higher supply voltage. I am aghast. This certainly could explain the erratic behavior I saw occasionally. I replaced the supply with the proper voltage.

I also chose to swing the two logic gates (A and B) closed and shut the machine, thinking that I was done with the hell of the resistor panel, but apparently something went wrong from the tiny movement of the wires while closing. The machine sits in permanent reset state. Either the Reset wire pin popped out of the resistor panel or the vampire tape for Reset came loose.


My burnishing has helped quite a bit. I was able to validate that most of the malfunctioning keys are now sensed correctly. S and most special characters that were failing now come up correctly. Alas, the cent sign is still not working, which might be oxidation on the latch on its keystem. Also, the 0-8-2 key should trigger a line feed but doesn't seem to work. I will need to do more checking to see what is happening here.

With a bit more usage, the cent sign (shifted R key) is registering properly. Only the 0-8-2 key stubbornly refuses to be read as a request for a line feed from the diagnostic. Time to study the keyboard wiring diagram to figure out what latch and bail contacts are involved in this - then of course any bails that work properly for other keys can be excluded. What remains, probably the latch under the key (0-8-2 is shifted T) is the culprit. It works fine except for that one character. 

No comments:

Post a Comment