MVH4 No sound with weird mod

juanchomvs

n00b
Joined
Jul 26, 2012
Posts
38
Hi forum

I recently purchased a 4 slot mvs that according to the seller had only a sound issue. I think is a z80 issue or a ym2610. the thing is once I inspected the board I found some interesting things...
I am not expert but I dont think these things should be there. Can someone tell me what kind of mod is this? I dont think this was made to repair something. Please help I am just a newbie
 

juanchomvs

n00b
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Jul 26, 2012
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Sorry this might help
Do you think this has something to do with the sound issue?
 
Last edited:

ack

Ninja Combat Warrior
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Apr 9, 2009
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Those are both common/factory mods. I have many MV4 boards with them.
 

sr20det510

Guerilla Warrior
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Oct 31, 2016
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That is good news! Thank you for your response
I’ll replace the z80 chip and see if that fixes the audio

Have you tried a recap kit to fix the audio in your board?

I think that is usually what causes the audio to eventually go out.
 

RyuX

Crossed Swords Squire
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What kind of sound issues are we talking ? Do you get distortion or parts of the sound missing - or are you missing all of the sound ?

The Mod on the Pro-B0 is bypass capacitors to ground to filter the WR1/2 and WR2/1 lines (it seems).
The other mod on the LS161 is a pulldown resistor (to ground) to bring down the signal on the QA Output of the counter.

I don't have the details of why they needed to mod this but I am pretty sure it was just to bring the signals within the tolerance range.
 

RyuX

Crossed Swords Squire
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Ah I see.. I am no expert with the MVH4 but are you sure that your power supply has the 12V Line properly connected and working ?
Do you get any sound pre-amplifier circuit ?
 

juanchomvs

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Jul 26, 2012
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Yes the 12v line is properly connected. I get no sound at all thru the head phone jack or jamma Adapter. I bought a cap kit is arriving on Monday paid $10 for it if it does not fix the audio is ok I can simply change the z80 and see
 

juanchomvs

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Jul 26, 2012
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Ok so I had a problem with the cap kit shipping is pending and I just couldn’t wait
I changed the z80 chip and now I get some sound but some tones sound awful
And the rest of the music is ok

What do you think is the prob?
A capacitor ?

This is what I hear
[video]https://streamable.com/2pcsh7[/video]

So there is some improvement
 
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Neo Alec

Ned's Ninja Academy Dropout
20 Year Member
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Dec 7, 2000
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11,927
Ok so I had a problem with the cap kit shipping is pending and I just couldn’t wait
I changed the z80 chip and now I get some sound but some tones sound awful
And the rest of the music is ok

What do you think is the prob?
A capacitor ?

This is what I hear
[video]https://streamable.com/2pcsh7[/video]

So there is some improvement
What does it do with a real cart? That sounds like a problem with the game to me.
 

juanchomvs

n00b
Joined
Jul 26, 2012
Posts
38
*Update* I finally received the cap kit!
I have now replaced all caps. I also removed the resistor on the chip since there was no noticeable difference with or without
But sound is the same...

Should I start checking for bad ym2610?

Please help almost there...
 
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juanchomvs

n00b
Joined
Jul 26, 2012
Posts
38
Ok i received the chip today “ ym2610 “from China. I installed it and now werks!!

Thanks for your responses
��
 
Last edited:

Jonap

Mega Shock!!
Joined
Oct 10, 2006
Posts
100
Nice to see the motherboard works again! always is good news saving old retro material!.
 
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