Tuesday, March 3, 2015

'Punch list' of problems with the 1132 printer for further investigation, plus SAC Interface PCBs arrive


I cleaned up my program and pushed the printer to do print my name a ton of times. Next update to the program is to expand it to do this repetitively, spacing down one line each time. However, having run the printer quite a few times, I see both positive and negative signs.

Positive side - the image is getting clearer and everything is loosening up nicely. The test program does set up the print line with my first name repeated across the width.

Negative side - the missing column I had mentioned before. From time to time the program is firing for what it thinks is one character but getting another - for example the emitter says we have a D3 - the letter 'r' - but when it prints it is 'q' which is code D8. Spacing works fine but the carriage restore button is not functional - nothing occurs when I push it.

Missing column - still to do is my test with a storage oscilloscope to determine if the solenoid is trying to fire or not.

Mistaken character - I need to do tests with the storage scope to check signal quality of the encoding disk, as well as verifying that the hammers are firing when it thinks we have a valid character (R not a Q). This could be in the light-disc-photocell path, the photocell amplifiers, the SLT cards in the printer or in the SLT cards for the printer controller sitting inside the 1131 processor. The letter Q is immediately adjacent to R, which leaves the possibility that I just have to perform a timing adjustment to fix the sporadic problem.

Nonfunctional carrier restore - the button could be bad - I have had several of the same type oxidized permanently open - or it could be other circuitry or even the contacts for the carriage control tape. Scoping will help me determine this as well.


My PCBs arrived in San Francisco and were on a DHL van for delivery to me today. The FPGA board left Brooklyn last night and is somewhere in the US postal system, rocketing towards me like a snail on sleeping pills.

The boards look very good. A quick test with an ohmmeter verified the power and ground planes are correctly reaching key points on the board. Since most of the traces are visible on the top layer, it would only have been problems in the internal layers that could have been difficult to detect.

My PCB for SAC receiver and driver circuits (12 + 12)

In a few days I will have my kapton solder paste masks, allowing me to spread on the paste (which has microbeads of solder which melt in an oven to flow between the components and the board pads) and construct the boards. All the components are here waiting to go.

No comments:

Post a Comment