Monday, March 2, 2015

Driving the printer and checking its operation while waiting for my SAC interface boards

It was a very heavy work day for me today, but I did get to spend a bit of time with the system.


I worked on some code I can use to exercise the printer. This should work out any sludge and uncover any residual incorrect operation. It was built and tested on the IBM1130 simulator before transfer to the physical 1130.

My code wasn't perfect, but it did drive the printer and made me more confident in the basic soundness. I still see signs of residual stickiness but not that bad, and hope it can be worked out by exercise. As well, I still have one column not printing.

As I first entered the code, it printed three of the four letters of my name, but which one didn't print was random. This means my logic for counting down and searching through the list of characters is flawed. When I switched it from four characters to just one, it was printing different characters than I selected.

I think it most likely that there is a bug in my code, worth a bit of desk checking or single step execution on the simulator. I am still cataloging possible defects - the first known issue is the missing print column. I will put a scope on the solenoid for that column plus one that works fine, verifying whether the issue is mechanical or electrical. I could have a bad SLT card or wiring, or it could be a stuck lever.


The boards are on their way to me, having finished fabrication, left Shenzen and was put on an aircraft in Hong Kong. The shipment has ten copies of my interface board, each 6.5" by 3", which will have installed many surface mount transistors, resistors, capacitors and 36 small signal diodes. It landed in Los Angeles and has cleared US customs. This should arrive in just a day or two at this rate.

Multiple SAC interface cards ready for component placement and soldering

My FPGA board arrived in the US and slipped into the black hole of the US postal service on the 28th in NYC. Finally on March 2nd at night it arrived in Brooklyn - it must have ridden on a snail to take that long to move a few miles. It should return to our universe at my doorstep at an indeterminate future date, hopefully during this week.

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