Z80 error with MV-1 board

Greetings;

I recently bought a MV-1 board that was advertised to have sound problems. The seller said that sometimes the sound wouldn't work; rebooting the machine usually fixed it.

Board arrived, plugged it in, and of course no sound. The screen was filled with graphical garbage like the cart slot was dirty. Several cleanings later most of the garbage is gone, there's still a bit but it's a hell of a lot less than when I started.

I did some searching here in the forums and read that a Z80 error means your sound is kaput. I get a Z80 error any time I access the test menu, either from the test switch or booting without a cart. However, if you boot with a cart, it plays fine but without sound.

I'm going to continue cleaning the board, which may fix both the sound and the graphical glitching. If it doesn't, is there any easy way to fix this?

Would installing the Asian bios or the Unibios be a fix?

Also, would there be any reason a fucked Z80 would cause corrupt graphics?

-thanks

The Z80 works in conjunction with the YM2610 sound processor.
There is a watchdog within the Z80, which monitors any problems with addresses/interrupts, which will lead to the error message.
The no sound may be a red herring, usually an error message would appear (rather than the game run with no sound) with Z80 problems afaik.
Ive had problems with intermittent connection around the Z80, there is also the SM1 rom and 6116 ram chips associated with the processor, problem turned out to be dry joints and open circuit tracks. Run some solder on the IC pins, remember there is a layer of tracks sandwiched in the centre of these boards, they are not simply double sided so you may not see anything apparent. I dont think the Z80 or associated memory would be at fault.
Very vague I know, anyway good luck.

It sounds possible that the onboard z80 bios could be currupted. You see if there is a game in the system it uses the z80 rom from that, if there is no game it then uses the onboard z80 bios. In test mode it always uses the onboard z80 bios.

Raz

Thanks for both of your replies.

Yesterday I unhooked the cart port from the PCB, cleaned the hell out of everything, and then reassembled.

Now I get a Z80 error, everytime on everything; cart or no, test mode or not.

Will installing an particular Asian bios like some archived post mentioned, or possibly anything in the Unibios fix this problem? I'm all thumbs whenever it comes to precision soldering, so unless I can pop a bios chip for a fix this board is completely useless to me.

Azathoth said:

Thanks for both of your replies.

Yesterday I unhooked the cart port from the PCB, cleaned the hell out of everything, and then reassembled.

Now I get a Z80 error, everytime on everything; cart or no, test mode or not.

Will installing an particular Asian bios like some archived post mentioned, or possibly anything in the Unibios fix this problem? I'm all thumbs whenever it comes to precision soldering, so unless I can pop a bios chip for a fix this board is completely useless to me.

Click to expand...

The universe bios will get you past the z80 error screen but wether games will actually work is another thing.

Raz

Razoola said:

The universe bios will get you past the z80 error screen but wether games will actually work is another thing.

Raz

Click to expand...

They may work with no sound, which would at least allow some trouble shooting to be carried out. With the error message present its like a catch 22 situation.

Managed to remove the 1.3 Unibios from another cab I've got and tried it in the 1 slot last night.

It allowed me to get past the Z80 error message, but the problems still remain. Still no sound, and the graphics still have some strange glitching going on. It doesn't look like dirty cart garbage, it's not random enough to be that.

50$ wasted, oh well. Thanks a lot to both of you for your help.