SE/30 - ceramic recap causing distorted audio?

[freon]

Hi all,

I recently purchased an SE/30 from a vintage computer convention - it was sold to me fully working. Looking at the logic board to upgrade RAM last night I was at first happy to discover that it has been recapped. However, whoever did so possibly didn't do the best job.

Loaded up a fresh install of 7.1, tried out some games and noticed they all sounded dreadful. Although the startup chime comes out clearly and the sounds in the Control Panel come out okay, anything more complex, including most if not all game audio, comes out as a mess of distortion and clicking. This happens on both the speaker and over the external audio jack.

Looking at the board, all of the electrolytic capacitors were replaced with ceramic ones which I don't believe is the way to go about things. Notice the cluster of 4 in the bottom right audio circuitry - I think it's safe to say the problem lies here?

Anyone know what else might be going on here? Is it common procedure to recap using ceramic components? I assume from all the information I've gathered that electrolytic SMDs should be replaced with tantalums on these boards. Unfortunately I do not have the proper equipment or experience to deal with tiny surface-mount parts like these, so any pointers to those offering (better) recapping services would be much appreciated.

 

[archer174]

The ceramics themselves should be totally fine to use. There are debatable thoughts about the long term effects, but for this use they are functionally equivalent. The solder job looks ugly though. I would also suspect that the board was not properly cleaned. 

 

[techknight]

Needs cleaned, and the Address/Data lines need checked on the ASC. the ASC itself could be bad, but I havent seen one personally being bad. 

Check to see if you have serial port issues too, try and form a localtalk network if you have another machine and a cable. 

 

[freon]

I went ahead and cleaned the board extensively with contact cleaner, checked the traces and tested the data lines on the ASC and they all looked good. Sure enough, no difference.

I really think it's the ceramic caps, probably C6 specifically, to blame here, but again, I don't have the know how or the tools to deal with such tiny parts.

 

[Von]

Although the startup chime comes out clearly and the sounds in the Control Panel come out okay, anything more complex, including most if not all game audio, comes out as a mess of distortion and clicking. This happens on both the speaker and over the external audio jack.

Are you going to stereo speaker?  Isn't the output from the SE/30 mono?

 

[Unknown_K]

Replace the capacitor(s) in the audio signal path with electrolytic (doesn't have to be SMT style).