MVS MV-1FZ watchdog

Hi everyone,

I have a strange problem with an MVS MV-1FZ I recently purchased. I read extensively here looking for a solution to my problem but I can't figure it out.

I cleaned and did the 5v only mod to the board. I have already done this to another MV-1FZ that's working fine, so I'm certain that I've done this right.

I am also using a Unibios 3.3 that I've burned myself, which is also working.

To the issue now, the MVS boots up just fine without a cartridge to the crosshatch. I have no trouble with anything, calendar works, did a memory test for 10 minutes.

I also tried the DiagROM. All tests pass, individual tests pass, too. Memory test passes there as well for 10 minutes.

As soon as I put in a cartridge, either an original, or a 161 in 1, I get the watchdog with a quick reset and clicking. (Cartridges also working on the other MVS).

Anything I can try, or focus on?

Thanks!

Did the issue happen before the 5v only mod?

Some random things I would try/check

- check for corrosion on the interconnect between the main board and the slot board
- check that your 5V rail is actually 5V
- sounds like you have another MV-1FZ? try swapping the slot board to narrow down if the issue is on the slot or main board.
- boot with the diag bios and a game inserted. If it watchdogs it maybe an indication the program rom(s) on the cart are enabled when they shouldnt be causing a data bus conflict and crash/watchdog.

Hey, thanks for the reply!

- I have checked for corrosion, there isn't any. I have already cleaned all pins on both the riser card and inside the slot.
- 5V rail is 5.01v on the controller port. Using a 3a 5v adapter (the same one from the other 1FZ)
- I have not tried this yet, will give it a go.
- Booting with the diag bios rom and a cart triggers the watchdog issue. No cart = no watchdog issue.

Swap the working cartridge slot from your other MV1Z onto the faulty one and see what happens that way we can rule out it being a problem with the cartridge slot. reads like connections touching that shouldn't be.
BB