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Thread: MVH4 No sound with weird mod

  1. #1
    Member juanchomvs's Avatar
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    icon29.gif MVH4 No sound with weird mod

    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

  2. #2
    Member juanchomvs's Avatar
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    Sorry this might help
    Do you think this has something to do with the sound issue?
    Last edited by juanchomvs; 10-09-2020 at 09:48 PM.

  3. #3
    Edo Express Delivery Guy
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    Those are both common/factory mods. I have many MV4 boards with them.

  4. #4
    Member juanchomvs's Avatar
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    Quote Originally Posted by ack View Post
    Those are both common/factory mods. I have many MV4 boards with them.
    That is good news! Thank you for your response
    Iíll replace the z80 chip and see if that fixes the audio

  5. #5
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    Quote Originally Posted by juanchomvs View Post
    That is good news! Thank you for your response
    Iíll 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.

  6. #6
    Member juanchomvs's Avatar
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    No jet do you advice to do a recap before I change the z80?

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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.

  8. #8
    Member juanchomvs's Avatar
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    I get no sound at all. Its completely dead

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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 ?

  10. #10
    Member juanchomvs's Avatar
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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

  11. #11
    Member juanchomvs's Avatar
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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
    https://streamable.com/2pcsh7

    So there is some improvement
    Last edited by juanchomvs; 10-30-2020 at 10:31 AM.

  12. #12

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    Quote Originally Posted by juanchomvs View Post
    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
    https://streamable.com/2pcsh7

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

  13. #13
    Member juanchomvs's Avatar
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    Quote Originally Posted by Neo Alec View Post
    What does it do with a real cart? That sounds like a problem with the game to me.
    Is not a cart prob all games sound like that. I have working 1 slot and they sound fine

  14. #14
    Member juanchomvs's Avatar
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    *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...
    Last edited by juanchomvs; 11-04-2020 at 01:35 AM.

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