Picked up a slugfest project.

Had a row of switches that did not work. Found the supply wire disconnected from the cpu. Reconnected the supply wire and the switch row worked. One of the switches in the row was an opto. While in switch test started to see the opto switch open and close several times on its own than the whole switch row failed again. The opto does not work nor will any of the switches in the row register in the cpu.

Looked for broken wires. Found none. Just wondering if a failed opto could have caused the switch row not to work or do I have a problem in the cpu?

Thanks

Update: So as it turns out, I have one row and one column out in the switch matrix. Both are associated with Opto's. Thanks to pinwiki, used the jumper technique to determine if the CPU was the problem.

In the Column case ( which has only 3 Opto's in the column) the CPU worked as it should. Ordered parts to repair the Opto problem.

In the row situation , the CPU did not properly register with the jumper technique. Pulled the CPU and looked for corrosion, did not see any leakage. Used a multi meter and determined there was no continuity between the pin and the first diode. Tried to reflow the pin solder to no avail. Looks like a problem with the trace. Will have some one local who is much better at board work take a look.

Thanks for the thoughts