All sorts of crash when trying to play game. Please shed some light.

[TheJeffChen]

This MV1ACH board came in in very bad shape (missing caps and scratched traces on the bottom) and was not even booting. I fixed all those and it's now at least booting my 161 in 1 cart.

However, it keeps resetting when playing almost all the games. I put in a Unibios and kept getting all sorts of errors.

Mostly:
- Illegal instructions
- Address error read/write

Some example of broken graphics:

Samurai Shodown 4's title screen sprites gets squished horizontally. Some other text sprites are also squashed horizontally. There was one case I was wiggling the board and the sprites actually changed width live.

Last sword gets totally scrambled image on the background.

I have a working MV1A and switched the cartridge board, but there was no improvement.

Interestingly, World Heroes plays totally fine. Neo DriftOut plays fine until the race is over.

I put the board into RAM test and the screen only shows "MAIN RAM TEST" even after 45 mins.

I burnt a diagnostic BIOS and all tests were passed.

I tried switching the two video chips (RAM 5&6) and nothing changed.

The thing I'm not sure are the missing SMD capacitors. I didn't know how big they should be so I put 100nF on all the missing ones.

Other than that, I'm suspecting this might be a bad CPU.

Please shed some light. Thank you guys!

 

[ballzdeepx]

What is your voltage at?

 

[a4ndr3c]

Does it resets with a legit cart? I have a MV1ach that fried some time ago and had that exact same problem with the 161-in-1 but with an original Metal Slug cart runs with no problem. I beat it even. Ironic that a MV1a China version had this problems with a chinese multi cart.

 

[TheJeffChen]

What is your voltage at?

Around 5.12V, same as my good MV1A.

 

[TheJeffChen]

Does it resets with a legit cart? I have a MV1ach that fried some time ago and had that exact same problem with the 161-in-1 but with an original Metal Slug cart runs with no problem. I beat it even. Ironic that a MV1a China version had this problems with a chinese multi cart.

I don't have a legit cart atm so can't test that. This one has huge letters carved into the black shroud saying "CHINA SALE ONLY" so is it possible that SNK put something special on the board to make sure it doesn't work with bootleg? Just wondering...

 

[TheJeffChen]

Here's some new info.

I checked the memory viewer and noticed some memory areas are repeating:

110000 - 1F003C: Repeat
C08000 - CE803C: Repeat
CEFFC0 - CEFFFC: Repeat
D00000 - DF003C: Repeat

Maybe one of the address line is stuck?

Edit:
110000
120000... All repeat the same content. Anything in between do not repeat. Same thing applies to other repeating range. There is definitely a stuck pin.

 

[BIG BEAR]

A legit cart will give you a better chance at repairing this unit. Those 161's have plenty of problems in their own right so it's going too be hard to tell where the problem truly lies.....
BB

 

[TheJeffChen]

A legit cart will give you a better chance at repairing this unit. Those 161's have plenty of problems in their own right so it's going too be hard to tell where the problem truly lies.....
BB

This 161 cart works fine on my good board. I'm just trying to fix a broken one. The problem can't be the cart.

 

[Macab0ne]

A while back I bought one of those MV1ACH as a back up and had the exact same issue with the 161in1. The 161in1 cart works perfect in my other board with no issues, but it just doesn't like the MV1ACH. It plays legit carts without any issues though.

 

[TheJeffChen]

A while back I bought one of those MV1ACH as a back up and had the exact same issue with the 161in1. The 161in1 cart works perfect in my other board with no issues, but it just doesn't like the MV1ACH. It plays legit carts without any issues though.

Comparing this one (MV1ACH) with my working board (MV1ACHX), I could see that one of the NEO-BUF chip was replaced with this orange passthrough on the MV1ACH. On the MV1ACHX there is actually a chip in place. I'm wondering if that's the cause. Ordering a PCB to build a DIY NEO-BUF... Let's see if the gotcha comes from there.