System 32 Garbled Audio

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    • System 32 Garbled Audio

      I've got 2 System 32 main board and I have 1 ROM board that I converted to Golden Axe 2

      On main board #1 the game plays and sounds perfect

      if I swap that ROM board to main board #2 the audio is bad.

      The problem is it sounds like the audio data is incorrect, so I get audio output but it's a bunch of beeps and buzzes (like an old school modem). I've heard this before with other boards while doing a conversion, usually if an audio ROM was programmed incorrectly, but I know the ROMs are good because it works on my other main board. (I have also dumped and verified the ROMs are good, just for good measure).

      RAM/ROM test in test mode comes back with everything as GOOD.

      These two boards were originally two halves of an Air Rescue setup and were supposedly in good working condition (indeed they're both very clean with no visible damage or rework anywhere on the PCB).

      Any idea what to check?
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    • stj wrote:

      compare any jumpers incase the "bad" board is set to use a different eprom.
      There aren't too many jumpers on the main board, but they all match... dips too.
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    • caius wrote:

      Not to repeat always same things but if you had an audio probe, you would easily pinpoint the fault in a certain part of audio circuit
      I understand how an audio probe can help when there is NO audio, but I'm confused as to how it can help when it sounds like the audio data is corrupted? I'm also confused how the Analog audio area could create what sounds like corrupted data. Please help me understand.
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    • caius wrote:

      Begin to use it and you will understand how it's possible.
      I already have some parts on order to build one. It takes more than a few hours to aquire parts... I'm not that good :)


      caius wrote:

      Not to criticize anyonebut perhaps you need some more experience on PCB to fully figure out how they works (I mean at hardware level)
      Well, I'm trying to learn but most of the time when I ask questions people just tell me not to bother because I don't already know.

      I don't want people to just give me the answer, I want to understand, Even simply giving me a link to some information to help me teach myself would be useful, but most people seem unwilling to provide even that.
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    • twistedsymphony wrote:

      Well, I'm trying to learn but most of the time when I ask questions people just tell me not to bother because I don't already know.

      I don't want people to just give me the answer, I want to understand, Even simply giving me a link to some information to help me teach myself would be useful, but most people seem unwilling to provide even that.
      Experience will give you answer.The more time you will spent on arcade hardware, the more knowledge you will acquire.There is no secrets in what we do.
    • caius wrote:

      Experience will give you answer.The more time you will spent on arcade hardware, the more knowledge you will acquire.
      There is an old saying: No amount of travel down the wrong road will lead you to the right destination.

      I know how valuable Experience can be, but I would like to be pointed in the right direction, so that the time I do spend on this is worthwhile rather than aimlessly wandering.

      ----

      So, for instance I know that I should build an audio probe, that's already underway. and I know I can look in the MAME source and identify which components on the PCB are used for audio and I can probably look up pinouts and data sheets for most of them... That's a start but what then?

      Should I just just start poking every pin on every audio chip... I'm expecting to just hear a lot of buzzing but that doesn't really help me because that's already what I'm hearing and I have no idea if that's what I should be hearing or not.


      caius wrote:

      There is no secrets in what we do.
      Then maybe you could tell me..

      When you trouble shoot an audio circuit which chips do you start with and why? Which pins on those chips do you listen to and why? What kind of sounds are normal, and what kinds of sounds lead you to believe you're on the path to determining the problem?
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    • twistedsymphony wrote:

      Should I just just start poking every pin on every audio chip... I'm expecting to just hear a lot of buzzing but that doesn't really help me because that's already what I'm hearing and I have no idea if that's what I should be hearing or not.When you trouble shoot an audio circuit which chips do you start with and why? Which pins on those chips do you listen to and why? What kind of sounds are normal, and what kinds of sounds lead you to believe you're on the path to determining the problem?
      With an audio probe you can "listen" to analog parts like OP-AMPs and amplifiers but also digital part with analog output like DAC and other IC with an embedded DAC (for example the OKI MSM6295).But I can say I use my audio probe also to "listen" to digital signal (for example serial data from the YM2151), you will obvioulsy hear scratchy audio (it's purely digital data) but at least you can get an idea if the system is running or not.

      The post was edited 1 time, last by caius ().

    • I'll check my boards when I'm back for specific suggestions... in general audio sections have data (roms), a processor (e.g z80), something with prebuilt midi instruments (Yamaha makes a lot of those), maybe another with prebuilt sfx, some chips for d/a conversion, a crystal for timing, and maybe a few other components like caps, resistors for attenuation, etc. You also have something that will mix the audio down to stereo from all those sources, and something that will amplify it (usually preamp and actual amp).

      I am still learning admittedly but I usually try to narrow down what's wrong in a sound test menu (is it MIDI music? Samples? Sfx?) and find where those come from, then trace around from there. I will look up the data sheet on the chip I'm poking at and just try to listen to the ins and outs.

      So when you have a probe and two boards, you will at least be able to a/b whatever you hear. Are all sounds corrupt? Could be the d/a, worth staring there since you are at least getting audio of some kind, just bad.
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    • @twistedsymphony

      I've learnt the best way to learn how to fix things is trial and error, reading loads of repair logs and datasheets.

      I'm trying to repair a system 32 board at the moment and there's zero information on these things apart from half a dozen repair logs. Even the CPU doesn't have available datasheets (and those that have them won't share)

      My understanding of your fault would point me in the direction of the Z80 - why? Because they regularly fail in the same manner on CPS1 and Neo boards. Quite often they used underrated Z80s to save money and they're now dying as a result.

      If your Z80 is socketed (I can't remember if the System 32 has it socketed or not) it's easy to replace it and see if that helps.

      The post was edited 1 time, last by xodaraP ().

    • xodaraP wrote:

      If your Z80 is socketed
      yeah I've seen a few repair logs where people had no sound and fixed it by replacing the Z80. unfortunately the Z80 on these is not socketed, so I'd like to confirm the problem is there before I go removing it.
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    • Mitsurugi-w wrote:

      Should be able to piggyback it I think.
      I'll have to try that once I get some more Z80s in. apparently I'm all out.
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    • My company just tossed a bunch of logic boards from a ElectoGlass wafer prober... They all had Z80s on them, but they weren't socket and I didn't have time to remove them... RIP. :(
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