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Thread: Mvh mv4 no sound from carts

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    Mvh mv4 no sound from carts

    I got ahold of this board that would only boot to the cross hatch screen and of course the battery leaked on traces. I checked continuity using a guide I found and wired points b5 and b6 on the cn10 connector. Now the board is booting games which I'm super excited about, but there is no sound not even the start up chime. If I go into test mode I can hear the beeps clearly. Where should I go from here? Did I miss a trace? I checked back through and I believe the rest were fine. Does anyone know what point sound comes through on? It's the 4 slot with the 3 white connectors. Any help would be greatly appreciated. Thank you.

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    Quote Originally Posted by Xian Xi View Post
    Clean the slots.
    Just cleaned all 4 slots used precision electronics cleaner and a toothbrush. Same result, no speaker sound no sound from headphones, test sound works from the test screen but beyond that absolutely no sound. When I slide the vol slider I do hear the speakers get louder with normal speaker hum. Can a bad trace near the battery impact sound? I'm getting continuity of .001 on all connections but a couple look bad, is it any harm to bypass those with wire if ye original trace is intact?

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    Quote Originally Posted by Xian Xi View Post
    Recap the sound section. You can buy cap kits from arcadecomponents.com, it's about 30 caps or so.
    Will do. I bought a set for my mv1 from there this week I'd say between the 50 caps I'll be putting in that my skills will go up another level at least

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    I agree with what Xian Xi said. If you didn't have a Z80 error and the sound is just too low then it's a problem on the analog side. Bad caps or (less probable) bad volume pot/amp chip.

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    Quote Originally Posted by furrtek View Post
    I agree with what Xian Xi said. If you didn't have a Z80 error and the sound is just too low then it's a problem on the analog side. Bad caps or (less probable) bad volume pot/amp chip.
    Yeah it's weird, because the test sounds work flawless just in game there is dead silence. I tried hooking a speaker up to the headphone connectors and they worked in test mode too, but still not in game. There was damage to the traces from the battery leakage I was curious if game sound would be impacted by this. I ordered the cap kit so I'll just wait and see If that fixes it when it gets here unless there is something else you know of that I could test/fix in the meantime. Thanks for the responses.

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    Sorry I misunderstood, I tought you were only getting very low volume with the test sound and in game. Recapping will only do some good but I doubt it'll fix the problem.
    If you don't have any sound in game then I guess it's on the digital side. That means it's between the cart and your board.
    The sound cpu is obviousy working fine with the onboard sound rom since you hear the test sounds right and you don't have a z80 error message, so it's certainly in between the slot and cartridge.
    I can't really guide you with pin numbers & shit where I am now, but if you can poke around with a scope or a logic probe, see if the M1 and V roms in the cart get enabled when the game's running (/ce and /oe pins going low).

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    I agree with furrtek. It's not the analog section/caps if the sound test menu is working fine. That same analog circuit is used for both that sound test and 99%+ of game audio so it wouldn't make sense. It's the board <-> cart M1 ROM connection like suggested. Z80 is crashing when trying to switch from the SM1 ROM on your board (does sound test, is OK) to the M1 on your carts (does game audio, will be mute if it can't be read properly).

    Extra things to check: Is there anything visibily wrong with the traces of Z80 + surrounding chips (AS244s,AS245) and also the traces that lead from that area to the white connectors? I see a set of long traces leading from there across the board to CN8.

    The cap kit won't fix this issue but the board must be 20+ years old and will probably need it in the near future anyway.

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    I misread that initially.

    But either way recap the board since it's gonna need it. Depending on how dirty your slots are it might be best to use a friction technique. Get a cloth and wrap it around a credit card and use the electronics cleaner solution and insert and remove a couple times, you'll be shocked at how little a toothbrush does in an MVS/AES slot.

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    Quote Originally Posted by furrtek View Post
    Sorry I misunderstood, I tought you were only getting very low volume with the test sound and in game. Recapping will only do some good but I doubt it'll fix the problem.
    If you don't have any sound in game then I guess it's on the digital side. That means it's between the cart and your board.
    The sound cpu is obviousy working fine with the onboard sound rom since you hear the test sounds right and you don't have a z80 error message, so it's certainly in between the slot and cartridge.
    I can't really guide you with pin numbers & shit where I am now, but if you can poke around with a scope or a logic probe, see if the M1 and V roms in the cart get enabled when the game's running (/ce and /oe pins going low).
    I ordered a logic probe (new toy to play with!) I never had/used one before but it said it reads high or low so it should work. So is there a guide for using a probe for this situation? Not real sure what I'm doing but I got till Wednesday to read up on it before it gets here thanks again for all the help and I'll try that credit card trick Xian!

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    I had an MV-4 with a problem like this - sound worked on the hardware test but not from any games. I replaced a bad bus tranceiver IC and now the sound is partly working. I suspect that replacing another tranceiver IC will complete the repair but I have not gotten around to it yet. I can send you a picture pointing out the IC I replaced and my prime suspect for the next one to replace if you want. I never would have found it without the help of a logic probe.
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    Quote Originally Posted by mjs256 View Post
    I had an MV-4 with a problem like this - sound worked on the hardware test but not from any games. I replaced a bad bus tranceiver IC and now the sound is partly working. I suspect that replacing another tranceiver IC will complete the repair but I have not gotten around to it yet. I can send you a picture pointing out the IC I replaced and my prime suspect for the next one to replace if you want. I never would have found it without the help of a logic probe.
    Sure thing any help will be appreciated. I got my battery holders and my cap kit for my mv1 that has screeching audio in so I'll try those two out on the mv1 while I wait for the logic probe to ship in.

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    Quote Originally Posted by Westcb View Post
    Sure thing any help will be appreciated. I got my battery holders and my cap kit for my mv1 that has screeching audio in so I'll try those two out on the mv1 while I wait for the logic probe to ship in.
    In may case one of the LS245 ICs below the YM2610 was bad (I don't remember if it was the one at F1 or the one at G1). I suspect that the neighboring LS244 is also bad but I have not gotten around to replacing it yet. Before going through the trouble of replacing any of them I would recommend confirming that it the IC in question is faulty with a logic probe and/or test circuit.
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    Quote Originally Posted by mjs256 View Post
    In may case one of the LS245 ICs below the YM2610 was bad (I don't remember if it was the one at F1 or the one at G1). I suspect that the neighboring LS244 is also bad but I have not gotten around to replacing it yet. Before going through the trouble of replacing any of them I would recommend confirming that it the IC in question is faulty with a logic probe and/or test circuit.
    Just recieved my logic probe today. Can you direct me to a guide on what and how to diagnose with it?

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    Quote Originally Posted by Westcb View Post
    Just recieved my logic probe today. Can you direct me to a guide on what and how to diagnose with it?
    There are two ways: The hard but best way and the easier but less conclusive way.

    The best way to do it for one-way logic is to get another of the same IC (LS244 for example) and hook it up to the same inputs as the IC you are testing and see if the outputs look the same. The only problem with this is when the IC you are testing is not always enabled and other parts of the circuit control the output lines when the IC you are testing is not enabled. So you will want to check the status of the enable lines to see if this might be the case. For bi-directional components it is more complicated because you will need to build a circuit to check outputs only when the IC is enabled and going in a particular direction.

    The easy way is to just power the thing up and write down the logic level of each pin when it is running, then compare it to a known working board. If you don't have a working one to compare it to then just write down what you get and I will try to read the same pins on my MV-4 for comparison. My recommendation is take the top board off completely and start it up - you will get the crosshatch screen. Use your probe to check the state of each pin of the left-most white plastic connector (near the YM2610). These pins are numbered A1-32 and B1-32. Classify each pin as one of these:

    N: no signal
    L: continuous low
    H: continuous high
    B: switching between high and low with about equal time in each state
    LB: switching between high and low but mostly in the low state
    HB: switching between high and low but mostly in the high state
    Last edited by mjs256; 06-20-2012 at 04:07 PM.
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    Quote Originally Posted by Xian Xi View Post
    Did you clean the slots yet?
    Yes sir. Credit card with a white teeshirt and lots of contact cleaner, it really didn't show much dirt, but I had cleaned it a couple times doing the toothbrush method. Also once it started up and had a blank screen and it said z80. I turned it off and on and it didn't show that again.

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    Hello! I activate this thread to know if anyone knows how to solve this problem, the same thing happens to me as Westcb. Making the sound test the speakers sound very good, but when I put a cartridge there is NO sound ...
    Replace the Z80 and LS245 but there are no improvements, including remove the pcb where the cartridges are placed and I did the sound test and it works: - /
    I already cleaned the 4 slots with super fine sandpaper and isopropyl alcohol, but there are no improvements ...
    Installing the unibios when selecting the JUKEBOX option, a message "error starting sound" appears

    Edit: I forgot to say that my system is mvs "neo mvh mv4"
    Last edited by redmec; 12-20-2017 at 08:40 PM.

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