Konami 573 audio 'noise' once game has booted/initialised

[tiff_lee]

Hi all,

Got a Konami 573 in a punch mania cab which has an audible hiss/noise once the game is fully booted to the intro screen, during all the initialising etc speakers are silent as if the audio output is disabled during this time. You can go into the test menu and it's silent until you enter the sound options and straight away it starts, exit sound menu and once again silence.

Exact same behaviour with two different 573's (audio is connected via the 4 pin header) and when using external speaker via RCA. I disconnected the CRT etc but as expected no change as the behaviour is consistent upon the game starting (or entering sound test menu).

Not sure if this is normal behaviour for 573 boards or perhaps a function of the game itself causing the issue. Once I have a lot more ambient noise I don't think it's going to be noticeable at all but I figured I would at least investigate it.

 

[awbacon1]

sounds like you are getting ground hum on the audio lines. All my Konami M2's do this as well...interference on the lines.

If you have a multimeter I'd check to see if there is any bleed between ground and the audio line

 

[tiff_lee]

If you have a multimeter I'd check to see if there is any bleed between ground and the audio line

Yeah I've got a multimeter but can you elaborate on what you mean by any bleed?

I'm no expert when it comes to audio analysis and the like so apologies if any of this additional data is useless.
I powered up the 573 on my bench and then fed the audio out of the board into my pc microphone input so I could capture and illustrate the issue better here.

What I found is that on the RCA output the 'noise' is always present and nothing changes when going from the main test menu into the sound menu.

Test menu RCA

Sound menu RCA

When using audio from the 4 pin header there is no noise when in the main menu, it only appears once you enter the sound menu (same as when the game finally boots up) although it is much more noticeable (i'm guessing because the audio is amplified)

Test menu 4 pin

Sound menu 4 pin

I did two quick videos capturing that sound graph and audio, i'm controlling the 573 via another screen and have no external screen capture stuff.
With each video the process is:

1. Start in main test menu
2. Enter sound menu
3. Play sound track sample (and turn up volume within the menu)
4. Stop audio sample
5. Return to main menu.

RCA Audio sample

View: https://www.youtube.com/watch?v=QugVVsEMAa8&ab_channel=lee3r24


4 pin header audio sample (note there is a big spike when going in and out of the sound menu)

View: https://www.youtube.com/watch?v=wPGfso_4krY&ab_channel=lee3r24


Oh yeah and I also had a quick look at the audio using my oscilloscope (was fumbling around somewhat) but when entering the test menu using the 4pin header output you actually have to re-adjust the scope as there is a 1.8V DC offset on the audio signal, whereas with the RCA output no change.

 

[awbacon1]

Yeah I've got a multimeter but can you elaborate on what you mean by any bleed?

I'm no expert when it comes to audio analysis and the like so apologies if any of this additional data is useless.
I powered up the 573 on my bench and then fed the audio out of the board into my pc microphone input so I could capture and illustrate the issue better here.

What I found is that on the RCA output the 'noise' is always present and nothing changes when going from the main test menu into the sound menu.

Test menu RCA

Sound menu RCA

When using audio from the 4 pin header there is no noise when in the main menu, it only appears once you enter the sound menu (same as when the game finally boots up) although it is much more noticeable (i'm guessing because the audio is amplified)

Test menu 4 pin

Sound menu 4 pin

I did two quick videos capturing that sound graph and audio, i'm controlling the 573 via another screen and have no external screen capture stuff.
With each video the process is:

1. Start in main test menu
2. Enter sound menu
3. Play sound track sample (and turn up volume within the menu)
4. Stop audio sample
5. Return to main menu.

RCA Audio sample

View: https://www.youtube.com/watch?v=QugVVsEMAa8&ab_channel=lee3r24


4 pin header audio sample (note there is a big spike when going in and out of the sound menu)

View: https://www.youtube.com/watch?v=wPGfso_4krY&ab_channel=lee3r24


Oh yeah and I also had a quick look at the audio using my oscilloscope (was fumbling around somewhat) but when entering the test menu using the 4pin header output you actually have to re-adjust the scope as there is a 1.8V DC offset on the audio signal, whereas with the RCA output no change.

That’s a hell of a lot of impressive information

https://www.techhive.com/article/58...es-from-your-audio-and-video-systems.html/amp

That’s a very cursory explanation and of course it could be caused by numerous reasons

 

[Starcade]

Hammy told me to put a ground wire to the external casing on mine (when it was generating humming sounds) and that did cure the issue with mine.