Repairing a Red Baron pcb

Zinfer

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Just punking around on this Red Baron board. Seems pin 40 on the CPU (6502) is blinking high and low. I traced this back by the drawing sets to L10 pin 8. However Pin 8 is high. This confuses me. I thought the signal from L10 Pin 8 ran directly to the CPU.
I also checked Pin 11 and that was blinking high and low. Traced that to M4 Pin 8 which is high.
At first glance I'd have said the problem is at L10 but it threw me when Pin 8 was high but pin 40 on the CPU was blinking high/low.
I exchanged and tested the 6502A CPU with a working Battlezone so I know the CPU is good.
I know that the dogs are barking, but where exactly do you start with a logic probe to find the source? Or is that even possible?
Any ideas?
 
That's normal behavior if the program isn't running. Have you ran signature analysis, or run fluke signs to make sure your address and data lines are good and are reading the eproms correctly.
 
I guess I'm going to have to pick up a fluke and some pods sometime soon. Maybe in the next year. As far as signature analysis. No, haven't attempted it.
I found that there was a missing 2N6044 transistor. After placing it, no dice still.
Think I'm gonna send this one off for repair. I've sat on it long enough.
 
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