mv1b no sound help please

[mr aize]

Hi everyone. Got my mv1b out of storage and there's no sound anymore. Definitely worked before being stored. Have recapped it but it hasn't helped. Only time I got any sound out of it was flicking the dip switch off when it was powered up, then it just made a bleep sound. Any help much appreciated.

 

[ack]

Try cleaning your cart and cart slot.

 

[BIG BEAR]

On the lighter side of diagnosing, a faulty volume pot will cause you to get no sound .
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[mr aize]

Thanks. Will try cleaning it. Tbf looks pretty clean but worth a go. Am I right in thinking there's no sound test function on a 1b? Also, how would I test the volume pot?

 

[BIG BEAR]

You are correct,no sound test with the MV1B. Adjust the volume on the pot and make sure there is no physical damage like a detached leg,replace it if you have a spare lying around
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[mr aize]

Hi again, any idea what the pot is? Size etc? Haven't got any spare lying around so need to order one.

 

[mr aize]

Never mind, figured it out, it's a 1k

 

[BIG BEAR]

Before you determine it's the pot that's bad, you can usually tell the pot is working by turning your tuner up then adjust the pot where you should here like a slight buzz as you increase the volume. Then you know it's not the pot.
I use parts boards to salvage alot of stuff.
If it's not the pot,it could be the z80. I've had to replace quite a few in my time dealing with that particular pcb.
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[mr aize]

ok so unfortunately it's not the pot. Changed it and no luck. Any way I can test the z80 before I go trying to change it? Also, where would I get a new one? Finally, because I haven't mentioned it already, the board has previously had a unibios kit installed by the last owner. It worked perfectly up until I put it in storage though, so didn't think that would be it.
Btw, thanks for the help

 

[BIG BEAR]

I sent you a link.looks like a good resource for other chips as well.
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[mr aize]

Thanks bud. As for testing it, do you use the neo diagnostic roms? Are they any good or is there another way to test? Don't want to get into surface mount soldering if it's not strictly necessary, but then again would have to find a sac game to use them to test the z80 right?

 

[BIG BEAR]

Thanks bud. As for testing it, do you use the neo diagnostic roms? Are they any good or is there another way to test? Don't want to get into surface mount soldering if it's not strictly necessary, but then again would have to find a sac game to use them to test the z80 right?

I -DO- use the diagnostic roms from time to time (they're great) but in this case,I personally would just remove and replace because I'm pretty sure the z80 is the culprit. If you want to use the diagnostic roms,you will need a PRG & a CHA pcb. you may also want to use sockets with those pcb's for easy swapping.
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[mr aize]

Fair play. Ordered one but it's coming from China so will probably take a looong time to arrive. Will update when I get it swapped.

 

[mr aize]

Right. So, changed the z80, no dice.. Any other ideas?

 

[BIG BEAR]

Right. So, changed the z80, no dice.. Any other ideas?

That arrived pretty quick.This is not a bad thing as that z80 will come in handy in the future for sure.
Anyway, you changed out the caps,right?
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[mr aize]

Yeah, caps was the first thing I changed, then pot, now z80. If nothing else I'm getting plenty of soldering practice .

 

[mr aize]

z80 ram?

 

[BIG BEAR]

z80 ram?

Yes.
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[mr aize]

Right. Finally got around to changing the z80 ram (took ages to come from china, then got busy doing other stuff). Anyways, unfortunately it's not that either. Are there any other possible culprits, or is it most likely one of the custom chips, which you can only source from another board?

 

[Neo Alec]

I assume you've been checking traces all along?

 

[mr aize]

I can't see any damage to any traces, but haven't tried belling them out. Honestly wouldn't know where to start...

 

[BIG BEAR]

I can't see any damage to any traces, but haven't tried belling them out. Honestly wouldn't know where to start...

I don't have a functioning MV1B but
I'm going to see if I can find a scrap motherboard in my pile to take a look at and I will return to this thread.
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[Atro]

I'm interested in this thread. I have two mv-1b's both without audio and no visible traces cut.

 

[Misos]

In my experience: Most of the times it's the Z80. A bad z80 mutes the sound.
I know it's counter-intuitive, but it really helps if you have a spare board with working sound, that way you can swap components.
For example, swap the z80 or the ram from a working board and see if that's the problem.
Of course the right thing to do is track down the problem, but it works.
Things in the MV1b that can die and cause no sound are: z80, z80 ram, the little Nec chip, Yamaha 3016, Yamaha 2610, capacitors and the 12v regulator.
You can bypass the 12v and do the 5v mod, feeding 5v into the yamaha chip.

 

[Neo Alec]

What does the Diagnostic bios say?