[FALSE ALARM FIXED] MV-1C CMVS project displaying flashing rainbow colors or NOTHING.

[Finch]

Plugged into my test PVM it either displays dark sort of fuzzy rainbow bars that flash across the screen (not clean pixels or anything, like completely blurry video isn't right sort of colors) when using composite or when I use RGB it just displays black. Tried S-video too and it was the same as composite.

The board worked fine until just recently. I'm only hooking up 5v, I've done the audio amp+caps removal already. Done the battery mod. These were all done as per Jamma Nation X tutorials. At that point the board still worked. Only thing I've really done since then is remove the BIOS to install a NeoBiosMasta. I know you can just lift a few pins, but I have a desoldering heat-gun and I wanted to use the BIOS on another MV-1C board that needed one. Once I installed the BiosMasta and my shiny newly-upgraded Unibios it stopped working. I tried a second NeoBiosMasta and same issue. I re-soldered the original bios and checked every leg to make sure they were soldered properly. Still nothing.

I've tested my test harness with a known working board and everything was fine. I also (on a whim) plugged in the board that is missing a BIOS chip and got the same load of nothing.

So it feels like something maybe isn't getting power, the BIOS isn't powering and thus nothing else is doing anything.

Any idea of where to start?

 

[Dropwire]

If I am not mistaken doesn’t the NeoBiosMasta clamp/clip over the existing 68k processor and then you still need to run 2 jumper wires? Maybe it pushed in or shorted a pin connection? If you want I have a few working MV-1Cs I could check the logic levels at the Original BIOS and send you the readout, if that would help.

 

[NeoTurfMasta]

What was the problem?

 

[Finch]

What was the problem?

Fuse actually, so I feel pretty stupid. it must have been nearly blown or failing already and worked well enough to test the board earlier. I removed it to make it easier to get to the bios and I think popping it out and then back in again made it crap out. I traced the 5V line from the bios and realized it didn't get past the fuse. Replaced fuse and it works. It was a VERY dirty board, it's seem some shit. Could have also been corrosion/dirt on the fuse holder and it wasn't making good contact. I cleaned it and with the new fuse it works. I would have realized earlier had it looked blown, but it looked fine.