LyonsArcade
Well-known member
Hi Guys!
I'm working on all kinds of stuff tonight, and one thing tha'ts been on the back burner for a while is a Centipede PCB I've got in a Centipede Mini. There's a weird issue with it:
The screen jumps vertically (side to side with the vertical monitor), but only when the board is cold (just been plugged in). If the pcb is in test mode, the screen never jumps. Also I don't get any bad ram beeps when the machine is in test mode. I've tried the board in another centipede cabinet, and it does the same thing in the other cab.
The mini has had the big blue replaced, and all the voltages test out good. I initially started replacing some of the things in the sync circuit, but since it doesn't do it in test mode, I stopped that since I don't think that's the issue. I tested R136, replaced ab10 - 7407, switched P4 (I think this is the sync chip) with another one from a parts board I have... but now I'm looking for something else since it only does it when not in test mode.
I pulled and tested all the roms, everything checks o.k.
Anybody have any ideas on where to look on the board? I'm trying to wade through the schematics right now.
I'm working on all kinds of stuff tonight, and one thing tha'ts been on the back burner for a while is a Centipede PCB I've got in a Centipede Mini. There's a weird issue with it:
The screen jumps vertically (side to side with the vertical monitor), but only when the board is cold (just been plugged in). If the pcb is in test mode, the screen never jumps. Also I don't get any bad ram beeps when the machine is in test mode. I've tried the board in another centipede cabinet, and it does the same thing in the other cab.
The mini has had the big blue replaced, and all the voltages test out good. I initially started replacing some of the things in the sync circuit, but since it doesn't do it in test mode, I stopped that since I don't think that's the issue. I tested R136, replaced ab10 - 7407, switched P4 (I think this is the sync chip) with another one from a parts board I have... but now I'm looking for something else since it only does it when not in test mode.
I pulled and tested all the roms, everything checks o.k.
Anybody have any ideas on where to look on the board? I'm trying to wade through the schematics right now.
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