Z80 Error on 4 slot MVS

Fusion916

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Bought a 4 slot on ebay awhile ago but haven't had the ability to test it until today.

Well low and behold I get Z80 error on boot. Doesn't matter what game is plugged in or no games plugged in. Even though the seller claimed it was working and had a picture of it working he sold it as-is so I can't really get a refund.

What are the debug steps from here? I can fix it myself if I have some guidance.
 
After researhcing some threads, I got a list of problems which can cause the Z80 error:

Dirty cart
Dirty slot
Z80 CPU (very very common)
6116 SRAM
74245 latches
YM2610 (very very rare)

Since I get this error any cart or no car, we can scratch the dirty cart/slot problem, with the Z80 cpu the likely cause. Is there any way to verify if the Z80 has failed or should I just blind swap the Z80 for a new one? Also, there are a lot of Z80 clones of various speeds, which Z80 should I replace it with? Does it matter?
 
Z80 speed is backwards compatible, so if you get the Z80b it should be fine, as far as I understand. They're relatively cheap, too, a couple bucks + shipping.

I'd try cleaning your carts/contacts as well, although I believe the 4 slot is supposed to boot into the test menu even if there are no carts supplied.

Can also check voltages to make sure they're within tolerance, although that probably wouldn't cause this issue either.
 
Cool, I'll just get the fastest Z80 then. Yeah I have read that the 4 slot is suppose to go to the crosshatch screen so that's how I know the issue is with the board.

I don't believe there is anything wrong with the voltages or anything because the board powers on enough to display graphics (video hardware and logic is working) and is enough to know the problem is with the Z80. Usually if there is a voltage or power delivery problem, nothing boots. I might just end up replacing all of the components related to the Z80.

Z80 speed is backwards compatible, so if you get the Z80b it should be fine, as far as I understand. They're relatively cheap, too, a couple bucks + shipping.

I'd try cleaning your carts/contacts as well, although I believe the 4 slot is supposed to boot into the test menu even if there are no carts supplied.

Can also check voltages to make sure they're within tolerance, although that probably wouldn't cause this issue either.
 
Anybody know where I can get a direct replacement for the YM2610? Is there a newer chip that is a pin for pin replacement?
 
The only place to get it from is a parts board... I have a few here that I haven't parted out yet.

Have you replaced the Z80 yet? Have you check for gouged traces on the board?

RJ
 
The Z80 processor uses a ROM on board the system to run code for some games and for test modes, but generally runs code from the cartridge which disables the onboard ROM.

What happens is if the cartridge slots are dirty the Z80 will lock up or crash and you'll get the Z80 ERROR message on the screen.

I think in your case the voltage levels were low enough that by the time the +5v got to the ROMs on the cartridge they were very low and the chips didn't operate properly. Hence the Z80 CPU locked up and you got the error message.

RJ
 
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