I have a single lamp out on the LAH. It is the E in CRANE. I replaced the bulb, reflowed the solder on the lamp pad and pins on the lamp board. I switched the lamp socket around to other positions. No change.

The Row and Column Transistors test good. But if one of those was out, I assume an entire row or column wouldn't work.

I checked the pins on the MPU board and they all look good. Wiggling the connectors doesn't do anything.

There are two ICs and a Zener just above the big white resistors which is browned. Could a bad IC cause one lamp to be out? Are there good substitutes for 7406s and LS08s as I don't have any of those but I do have some others which are close?

I forgot to add that diode tests good. But I will replace it anyway.

Here is a pic of the IC after I cleaned it.

MPU (resized).JPG

OK. Good to know I don't need to mess with the board.
Thank you both.

It was the diode. Weird. It tests fine even after I removed it. Thank you.