Mac Color Classic: no sound from speaker or headphones socket

[nvdeynde]

I've recently acquired a Color Classic with a recapped logic board ( tantalum caps ) but capacitors C1 and C2 had the wrong value, 47uf instead of 100uf and C1 was mounted with the wrong polarity as well.

The logic board has no sound, not from it's internal speaker but that can be due to a faulty audio amplifier on the analog board, but neither from it's headphones socket which is concerning.

I'm wondering if the 2 wrong capacitors on the logic board have destroyed the sound chip.

I have recapped the whole logic board just to make sure with the correct caps.

Can the sound chip be damaged because of the 2 wrong capacitors on C1 and C2  or can there be another cause why the board has no sound ?

 

[flyingforstatus]

I know this reply comes several months after the original post, but in case it is helpful to you or others...

I had a board come across my desk last week where I suspect that a capacitor had been installed with incorrect polarity and all sound is missing - both from the headphone jack and the internal speaker.  During boot, you only hear a "click" from the speaker.  If this had happened after a fresh recapping I had done, I would assume the board is dirty with electrolytic capacitor gunk and I'd wash it again and again.  But, since I knew this was a previously recapped and working board where the end-user replaced new electrolytic caps with tantalums, I bet on a polarity error during their installation (which can be easy with tantalums if you aren't experienced or paying close attention).

Troubleshooting/Repair steps:

1. I recapped the board (again) in the region of the sound circuitry (didn't fix)

2. I searched the web for "bomarc color classic schematics" and obtained a compressed file with all schematics for logic boards of this era from, I believe, archive.org

2. I checked all traces to nearby capacitors and the PLCC chip itself and all tested good

3. I had a donor board and hot air station handy so I decided to transplant the components labeled in red in the attached photo from a junk logic board to the one without sound

4. Sound was restored!

I didn't have time to thoroughly troubleshoot/test each component and since I had a donor board handy, I just replaced everything.  It's possible I replaced more components than necessary.  You might start with replacing D1 between L1 and L2 before going to the trouble of replacing the PLCC chip...

I've noticed that these components are on other logic boards of the era, so my assumption is that you don't need an exact donor match.  That means you could find a similar board of the era with the same components to use as the donor.  As an example, I have successfully transplanted these components from a Color Classic donor board to an LC575 Mystic board.  Currently, I buy Color Classic donor boards on eBay but I'm sure that there are many more common and less expensive options. 

Good luck all.

 

[sammyfox]

Hi there! I'm sorry for replying to such an old thread but I wanted to tell my own story.

I did the senseline vga mod for my new color classic but it's a stock machine and apparently that doesn't work with stock CCs so I had to undo the mod.

Once that was done I only hear weird noises and then nothing when switching on the macintosh. I was at a loss as to what could be causing this (same symptoms, no sound from speaker or headphones jack) until I looked at the analog board and realized I hadn't plugged back the grounding clip (I included a photo to show what I'm talking about), and so I shut down the computer, plugged the clip back where it was supposed to be, and when I switched back the computer on that pretty chime rang and all was well.

So yeah, that's something you could check.

 

[gobabushka]

Hi there! I'm sorry for replying to such an old thread but I wanted to tell my own story.

I did the senseline vga mod for my new color classic but it's a stock machine and apparently that doesn't work with stock CCs so I had to undo the mod.

Once that was done I only hear weird noises and then nothing when switching on the macintosh. I was at a loss as to what could be causing this (same symptoms, no sound from speaker or headphones jack) until I looked at the analog board and realized I hadn't plugged back the grounding clip (I included a photo to show what I'm talking about), and so I shut down the computer, plugged the clip back where it was supposed to be, and when I switched back the computer on that pretty chime rang and all was well.

So yeah, that's something you could check.

View attachment 36486

Would the system boot at all? Or did it just make weird noises? DId the front light blink? I ask because ive been trying to diag my own cc

 

[sammyfox]

It did boot, it just didn't have sound.