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Velyks

Student
Joined
Jul 31, 2019
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London
Hi,

I've got a strange issue with a very slightly rotten top board (the bit with the cartridge slot) on an MVS MV-1B, my guess is there is a trace broken somewhere but there isn't anything glaringly obvious. Swapping it for a known good top board fixes the problem.

The symptom is every pair of columns for the sprites is back to front.

The pixels should be:
1 2 3 4 5 6 7 8

Instead they are:
2 1 4 3 6 5 8 7

Here's some pictures of the problem on an Aero Fighters 2 cart. https://photos.app.goo.gl/FiCUiuf1kKVmUZya7

Does anyone know what pin or signal could be responsible for this? That'll hopefully narrow my search down from having to try and beep out 240 pins.
 
All the traces look fine and I've scoped it, the ZMC2 is receiving a good EVEN signal which I think sadly means the ZMC2 is dead or in the process of dying.
There are replacements on ebay but they cost almost the same as a MV-1B.
 
I assume you saw the signal pulsing right?

You might try reflowing the zmc2 first just to rule a loose solder joint.
 
I've taken the whole chip off (to solve another problem tracing some pins) and put it back on, and it sadly didn't make a difference.
 
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