Macintosh Colour Classic - no sound

[AlpineRaven]

Hey All, 

A mate of mine bought an Macintosh Colour Classic, when he obtained it obviously the board has leaked the caps out of it, when you switch it on it doesn't have sound at all, which is caps of course.

Last night I/we recapped the board with him, teaching him how to re-cap it. All caps have been replaced 47uf, 100uf and 10uf ones - all correct value as per spec. (I've done other 5 CC boards same as this one and have bene successful)

Plugged the board back in CC, waited for startup chime, nothing, once the finder loads, went to Sound control panel - no sound output. We decided to plug the speakers in - it does have sound via speakers.

What else should I check? Doesn't sound jack have pass thru for internal sound?

Cheers

AP

 

[rickrob]

I'm pretty sure that the sound out for the internal speaker goes to the internal edge connector.

Check for open traces around the caps --  You'll have to follow the traces from the DFAC 2 chip to the Sound amp chip to the  connector. Check the block diagram in this developer note.

https://powercc.org/downloads/files/Mac Color Classic.pdf

https://cdn.preterhuman.net/texts/computing/apple_hardware_devnotes/Mac LC 575.pdf

 

[TjLaZer]

I have the same issue and found out I have a burned transistor at DD1.  Take out the Analog board and inspect it.

https://68kmla.org/forums/index.php?/topic/54678-burned-transistor-on-cc-analog-board/