Thought I'd give you something to read. It's not really a technical fix, but it's a read.
After repairing a NARC soundboard, I thought I'd test which of the components were duff (most of them as it happens). I stumbled on this by accident on what was a faulty Mortal Kombat PCB, I'd given up on. I had no ROMS in the Main PCB, just the boot ROMs U89 & U105. They're enough to make the sound board go bong.
Without all the ROM chips though I got a U99 error.
This is what the PCB was originally doing - corrupted text in game. The test screen text was fine though.
Having got that error I decided to take a closer look around U99 and almost hidden beneath a capacitor is a scratch going through 2 traces - very difficult to spot and had me beaten originally. Amazing where damage occurs and how it can reach that place of all places.
Very awkward location between the socket and CPU and the scratch is at a change of direction for the trace - bad location again.
Managed to solder in 2 trace wires of 0.2mm diameter wire, took a while because it was truly awkward.
Replace the capacitor and it's all good again.
After repairing a NARC soundboard, I thought I'd test which of the components were duff (most of them as it happens). I stumbled on this by accident on what was a faulty Mortal Kombat PCB, I'd given up on. I had no ROMS in the Main PCB, just the boot ROMs U89 & U105. They're enough to make the sound board go bong.
Without all the ROM chips though I got a U99 error.
This is what the PCB was originally doing - corrupted text in game. The test screen text was fine though.
Having got that error I decided to take a closer look around U99 and almost hidden beneath a capacitor is a scratch going through 2 traces - very difficult to spot and had me beaten originally. Amazing where damage occurs and how it can reach that place of all places.
Very awkward location between the socket and CPU and the scratch is at a change of direction for the trace - bad location again.
Managed to solder in 2 trace wires of 0.2mm diameter wire, took a while because it was truly awkward.
Replace the capacitor and it's all good again.
