2-slot MVS shows fucked-up symbols

[Amano Jacu]

If I start it with its bios (or another original one I had around), after the green ram test it goes to a screen with a lot of "%" and some random letters. With a unibios, the games starts but all graphics are garbled up.

Any idea of what could I do? Thanks. I'll post pics if needed.

 

[chris1]

It's all I can think of..

Hmm..

I'd say...Try re-seating the bios chip in the socket..

 

[Amano Jacu]

Already tried 3 different bios with the same results... :/

 

[werejag]

inspect the traces coming from the bios area.

 

[channelmaniac]

Post pics please....

Sounds like you may have a column problem on a static ram chip.

RJ

 

[FalcomAdol]

If you're going to the test screen with a cart in one or both slots, it's possible that the cart slot and or cart connectors are dirty.

 

[billd420]

Isn't that the tell-tale sign that your video ram is toast?

-Bill

 

[channelmaniac]

Maybe...

I've seen funny characters show up on the screen when there were broken traces and/or problems on the top board and when there was a failure in the Video SRAM (cxk5814) chips... The failure was such that the lower 1k and the upper 1k banks weren't being addressed correctly and the chip would pass RAM tests but corrupt data while in use.

RJ

 

[Amano Jacu]

I've checked the bios traces and I can't find anything wrong in them. Here's some pics:

Unibios and no cart: I get to hardware test menu and I can cycle through it, just with garbled graphics:

http://members.lycos.co.uk/amanojacu/fotos/snk/P5220001.JPG

Unibios and Kizuna cart: game starts as normal, just fucked-up:

http://members.lycos.co.uk/amanojacu/fotos/snk/P5220002.JPG

regular bios (no matter if a cart is in or not): just this message, which I guess is some kind of error message I can't read due to the error itself

http://members.lycos.co.uk/amanojacu/fotos/snk/P5220003.JPG

 

[channelmaniac]

My vote is on the CXK-5814 SRAM ICs.

RJ

 

[Nightmare Tony]

Wrong RAM. If you are seeing bad text such as % signs all over, it is the FIX RAM which is attached to LSPC-A0. This RAM holds the text table and the first pallete table. I would bet dollars to doughnuts you are looking at loose pins on the LSPC-A0.

 

[Amano Jacu]

Thanks... How can I locate those RAM chips? Are they labeled accordingly?

 

[Nightmare Tony]

The FIX RAM are the 43256 RAMS attached to the LSPC-A0. The 5814s are also attached to the LSPC-A0 and serve to define the sprite attributes lookup table.

 

[Amano Jacu]

I've found a square chip called LSPC2-A2 and it has two 5814's next to it.
The surface around the LSPC2 looks a bit damaged, so maybe it got fried. I could post a close-up pic of it if needed.

 

[Nightmare Tony]

A2 is the newest version, same thing applies. If the chip top is bubbled or cracked, it COUJLD be doing it, but I have yet to see it show symbolbs. If the LSPC blows out, it invariably leaves a dark screen and tends to hit the A0 rom as well as the 5814s.

A2s are more rare for blowing out compares to A0s.

 

[channelmaniac]

Hey Tony!

Are the LSPC-A0 and A2's interchangeable? (pin-for-pin and function?)

RJ

 

[Nightmare Tony]

Functionally they are sim,ilar, pinoutwise, nope. I think the A2 may incorporate the internal fast RAM that was previously inside of B0, but not sure. It hasd been ages.