4-Slot (MV4) Garbled Video

[monads]

It worked fine. Then I swapped out the stock US bios with a unibios 3.1v and got the garbled image/text. Only thing I can thing of;

1) unibios not making contact/sitting perfectly
2) corrupted RAM

I tried removing and re-sitting the unibios in the socket to no avail. If it's the RAM how do I fix?

 

[Jibbajaba]

Just out of curiosity, did you try putting the stock bios back in?

 

[monads]

I did. And got the same problem

 

[Xian Xi]

It's most likely the connection between the boards. Make sure they are seated properly. If you are using bolts on the connectors, make sure you don't over tighten them.

 

[monads]

Thanks Xian, I'll double check again tonight. I didn't use the bolts to fasten since I wanted to make sure all was working befere securing.

 

[monads]

Couldn't get it to work. And I tried swapping boards top/bottom with other MV4 working boards as well.

Swapping bottom out only: slots 1&3 garbled video, slots 2&4 normal
Placing bottom back and swapping top out: all slots garbled video.

 

[Asure]

Seems strange that a board can go so bad after inserting a bios chip. Did you damage anything by accident, drop solder splotch on the board or something?
Can you take a few pics of the garbled video, so we can get an idea what sort of problem is going on? (I had a similar issue recently, so may be easy to solve.)

 

[monads]

I'll take some pics later today. After I did the battery mod and tested I set the the board aside awaiting the unibios arrival. After that, it went south.

 

[Asure]

..After I did the battery mod..

There's a few pcb tracks related to graphics near that battery and some stuff from CN9 is also responsible. But let's see those pics first

 

[monads]

Here's some photos. Also started to get Illegal Instructions randomly.

Goal Goal Goal





Switching out boards trying different combinations just makes is worse:

Neo Drift Out

 

[Asure]

Wow, seems like you are missing at least ~6 adress lines for the graphics, maybe 3-4 more for the colors. This sort of damage must be pretty visible on the board, or some of the LSxx logic has gone bad on the top/bottom board.

- Do you have a multimeter and/or logic probe?
- Is this the old style, or new style board set (lots of small ic's on the top of the board = old style, 4 big smd chips)

The board is held together with four interconnectors that carry the data from the carts down to the main (bottom) board. This data then goes to the PRO-CT0 chip. It is unlikely that this is damaged: You say you can run games perfectly in slot 2 & 4 with a known good top board..

So this brings us back to the first thing Xian pointed out, the interconnectors. Check them for bent pints, it almost seems like there is a bent pin touching at least 3-4 other pins in one of the interconnectors.
I had a similar problem with one line of graphics missing which turned out to be CN9, but the stuff you are missing is way worse.

 

[monads]

Thanks Asure. I don't see any visual damage on the boards. I do own a multimeeter, but it's a crappy small portable one from Radioshack. It should work for continuity checks though. I don't have a logic probe. Maybe time to purchase. The top board has small ic's.

I'll tripple check the interconnectors and bent pins. Thanks for the assistance.

 

[ne7]

Before jumping in with the logic probe: try very, very gently wiggling the cart and putting a little pressure on the label of the cart at diff points on the slot that is producing screwy video - if that fixes it - clean the slot + cartridge edges... had video prob's like that all the time on various 4slots and its normally just that they need a good clean up (90% of the time) ...