MVS 4slot Z80 jumper nest

[erock]

Noob here, Picked up a 4slot recently knowing it had some issues. Occasional Z80 errors, garbled/no sound.

Installed Unibios 3.3, loaded 4 carts in, skipped a Z80, no real graphic errors, all slots worked, but no sound. Started poking around the Z80 and found a decent number of jumpers... Anyone here have any ideas (just from looking at pics) as to what may have been the intent???

edit: I think a cap kit was put in as well.

Thanks in advance.

 

[HeavyMachineGoob]

The intent was probably trace repair, but that's nuts. That board should be sent to a professional.

 

[Xian Xi]

It's weird seeing trace repair on the top of a board.

 

[mikejmoffitt]

It's weird seeing trace repair on the top of a board.

For corrosion repairs, I'd expect it, but this one is just looney.

 

[erock]

For corrosion repairs, I'd expect it, but this one is just looney.

The battery area looked ok, it really seems that the z80 is the epicenter... heh.

 

[erock]

The intent was probably trace repair, but that's nuts. That board should be sent to a professional.

Yeah... I'm hesitant to start digging in this one as my first real project haha.

 

[bustedstr8]

It's a good idea to snip that old battery as well.

 

[erock]

It's a good idea to snip that old battery as well.

I'm dying to start snipping all of it hahah... but Yes! I'm doing it now!

 

[erock]

There she is! (on under side of board)... Ok this makes more sense now... yuck. Looks like he was playing with a mini light saber too close the work bench.

 

[Ukyo]

There she is! (on under side of board)... Ok this makes more sense now... yuck. Looks like he was playing with a mini light saber too close the work bench.

View attachment 34917

haha, you got this dude.

 

[erock]

haha, you got this dude.

Thanks man... This looks like a real 2 day vacation...

Battery gone.

 

[HeavyMachineGoob]

If that gouge is literally the only damage on the board, you could always reverse all the repairs on the top of the board and just patch traces under the board. The correct procedure would be to check what exactly all the old jumpers are patching exactly and see if they are related to the gouge. If there are no other repairs going on besides the gouge, then that's all you'd need to focus on.

Going by those first pictures though, it almost looks like the guy cut up some of the legs on those chips. If that's the case, I'd just replace the Z80 and SM1.

Actually, you should replace the Z80 regardless. The MVS requires a Z80A, which has a faster clock speed. Running a Z80 at Z80A speeds will cause premature chip failure.

 

[erock]

...reverse all the repairs

Ah- I was thinking of doing that... You sir may have convinced me.

...just replace the Z80 and SM1.

I found several Z80As online, not sure what the SM1 is (yet).

...Running a Z80 at Z80A speeds will cause premature chip failure.

I was reading about the different versions on another thread and then I saw that there was "Z80a" actually printed on the board. Thanks for answering a future question!

 

[erock]

Whelp- Thanks everyone for the info. I regret not flipping the board over first... I was so surprised by the wire job I skipped some due diligence.

The clipped "150" resistor above the Z80 has me worried...BUT:

Z80a is on its way, I'm off to the cellar to re-trace this thing. Thanks again!

 

[HeavyMachineGoob]

If the SM1 hasn't had any of its pins cut and lifted, then just clean up the pins and leave it alone.

SM1 is a ROM chip, it contains generic Z80 code. The ROM file for it can be found in the common neo-geo.zip MAME archive.

Yes, swap out the Z80 for a Z80A, maybe add a socket while you're at it. That is if you don't need to solder any wires to it on the top side of the board.

 

[erock]

Update:
Re-worked all the existing jumpers, clean cut questionable/damaged traces and ran all new jumpers (It looks like all were related to the gouge, thank you).
SM1 "looked" good once I cleaned it up.
Ran the cab for a couple hours: no errors/glitches other than no audio & consistent z80 errors during HW test (empty current/expected values fwiw)
I'm looking for Z80 pinouts for the 4 slot ATM.
Should I be worried about the clipped "150" resistor (last pic)?
Z80a & IC burner should be on their way.

Thanks so much.

 

[erock]

For the curious:

Still ratty, but easier read. (I'll tac it down later)


Much better considering the giant gouge on the other side.

 

[RetroTechRewind]

For the curious:

Still ratty, but easier read. (I'll tac it down later)


Much better considering the giant gouge on the other side.

Looking good! No issues after the fix?

 

[VaNDAL_UK]

No too bad of a repair. I would suggest some Kaynar wire or some enamelled copper wire for a more permanent & clean job. Next I would:

1: Replace the resistor.
2: Just replace the z80 (if you have no way of testing.
3: Continuity test anything that look suspicious.

 

[erock]

No too bad of a repair. I would suggest some Kaynar wire or some enamelled copper wire for a more permanent & clean job. Next I would:

1: Replace the resistor.
2: Just replace the z80 (if you have no way of testing.
3: Continuity test anything that look suspicious.

Considering my noob-ness, I will take that as a high compliment sir! I will swap out wires when it's sorted, Kaynar it will be.

1) I believe that's a brown/green/brown/gold resistor I am looking for. (?)

2) Z80a- in the mail.

3) I'm getting really good at that part .

I can't thank everyone enough for their time on this.

 

[erock]

Looking good! No issues after the fix?

The original list was: general instability, random crashes, no/crunchy audio & occasional z80 errors.

After all this: a consistent z80 error, no audio. There were no other issues present after running for 4 hours with 4 carts loaded.

 

[RetroTechRewind]

The original list was: general instability, random crashes, no/crunchy audio & occasional z80 errors.

After all this: a consistent z80 error, no audio. There were no other issues present after running for 4 hours with 4 carts loaded.

Ahh okay, well at least nothing got worse! I'd bet it's a dead Z80. I've replaced quite a few in my time. Hopefully that will fix your audio issue!

 

[erock]

Update: Got the new z80(a) & socket in... get this from Unibios 3.3 & still no sound. Volume slider is pushing the speakers... just no audio.:



Does the lack of an address leave any clues?

 

[erock]

Should I tackle the SM1 or keep this guy for parts?

 

[HeavyMachineGoob]

Looks like the Z80 is completely inactive going by that error message. The only real means of diagnosis now is the Diagnostic BIOS + M1 ROM combo, you can get it at Jamma-Nation-X.

After that, you may want to go over your gouge repair to make sure it's fully working. The wires you recycled are way too big though, get some IDE hard drive cabling and use that, just peel each wire you need off the cable. If the gouge repair is good, then you'll be wanting to check over the rest of the bottom board for damage. Other than that, it'd just be bad parts to look out for.

The SM1 ROM shouldn't cause complete inactivity like that. Going by the MV-1B board, which doesn't have an SM1 ROM, I'd say it's an optional component. It just contains rudimentary Z80 code, something that every Neo Geo game has on the CHA board in the form of an M1 ROM chip.