Tuesday, January 17, 2017

All drive boards and cables working correctly, buffed up documentation


Board 2 with the new Diablo cable was not working properly, not reacting to when I turned on the SelectUnit1 signal via the slide switch. That signal is driven by one chip on my driver board which began to work when I pressed down on the leads. This tells me there is a bad solder joint there which I need to correct. When it worked, the file was extracted flawlessly.

After closely examining both boards 2 and 3 under the microscope and redoing any connection that was not clearly perfect, I retested the two with my new cable. Board 3 still does not select the disk with SelectUnit1 and let the FileReady signal activate, but board 2 now works perfectly. The extracted file matches 100%

Back to the microscope and the continuity tester for board 3 - this one is annoying me. The problem has to be in the lines for SelectUnit1 or the incoming FileReady signal, so it won't take too long to check it out (again).

Well, I had checked that the lines had continuity from input and output connectors and that the solder connections on the eight pins of the chip looked good, but I obviously didn't look to closely at the chip itself. It was soldered on upside down (not rotated 180 degrees but with the face downward on the PCB). Doh.
Chip mounted with bottom face upwards
It was a quick matter to remove the chip with a hot air rework tool, clean up the pads and solder on a new chip, this time oriented correctly. With that done, I took it over to the testbed and attempted to use it to read the cartridge image again.

This time it worked perfectly, extracting the entire cartridge and that image compared word for word with the known contents. Now I have three good boards and two good cables. I will be delivering a set to Al Kossow for use in archiving all the Alto cartridges he has.

I spent a bit of time updating the documentation to deliver with the tool. It should be usable immediately but I will go over its use one time when I deliver it.

The remaining time on Tuesday I put into planning for testing of the emulator role functionality for the tool. First come the schemes for how to drive the tool without a real Alto computer, then the mechanisms to implement the schemes, and finally the instrumentation needed to debug the tool as it attempts the various actions driven by the schemes. 

No comments:

Post a Comment