CPC 6128 sound problems

[llopis]

I just bought an Amstrad CPC 6128 to have fun with some hardware projects and relive days of my childhood. Everything seems to be fine (including the disk drive!), except for the sound.


The best I can describe it is that only the noise waves are generated. Pressing the delete key makes a tiny "bzzz" noise instead of the usual beep. When I play a game, I can hear the noise/drum tracks, but none of the usual square wave melody.


Could someone help me diagnose or narrow down the problem? I would suspect it's the AY chip that's acting up and needs replacing, but that's just a guess. Has anyone seen this before?


Thanks.

[llopis]

Oh, one more piece of data: When I plug in a headset in the headphone jack, I hear the same noise as the speaker (very faint since it's not amplified). So it's not the internal speaker.

[llopis]

Replying to myself since I'm getting some new information. Hopefully it'll give someone some idea of what might be wrong.


It looks like my initial assessment of only playing noise-wave sounds was incorrect. When I execute the command SOUND 1,100,100,10,1,1,30, it should make about a second of noise, but it doesn't. It just makes a very brief "chsk" noise-like sound. The exact same sound as if I press the delete key with nothing to delete (instead of getting the friendly "beep").


In most games the music doesn't play, or it makes an occasional "chsk" sound. The one that generates most sound is the music for Army Moves.
This is what it's supposed to sound (on an emulator): Dropbox - am_good.m4a
And this is what it sounds like: Dropbox - am_bad.m4a (which is just a bunch of "chsk" sounds with the correct beat).


So it seems that the sound system makes a "chsk" sound whenever any (?) sound commands are sent.


Does that mean the AY chip is likely to be bad? I also read the 8255 PIO could be the cause. I think we can also rule out bad capacitors since this is 100% consistent.

[Bryce]

Hi and welcome llopis,
          thanks for a well described problem. Unfortunately you are correct. If the sound problems are also coming out of the audio socket, then it's 99.9% an AY problem. It's very unlikely to be the 8255, because when that fails you just get no sound at all. The good news is that the AY is still readily available, so you just need to replace the AY or find someone who can do it for you. If you can't do it yourself or don't know someone local that can do it, you can send me the PCB and I'll repair it for you.

Bryce.

[AMSDOS]

Love the idea of a CPC buzzing at you when you press the DEL key   


It's a shame it doesn't play much else though