Classic II Very Faint Sound After Recap

[mooxitani]

I've just finished up recapping both the analogue and logic board of my classic ii, but i'm only able to get very faint sound out of headphones. I've already given the board a deep cleaning in IPA with no change. I did notice a trace that looked slightly suspect under C13, could that be impacting the sound, or does the board just require more cleaning?

Thanks in advance!

 

[Johnnya101]

Probably needs some more cleaning. Usually a trace is either good or not. If you are getting some sound, then its probably fine. Maybe cap goo stuck under some chips for sound? Classics are known for bad cap goo issues.

Anything on the speaker?

 

[mooxitani]

Tried putting my ear directly up to it, and I’m not getting anything. Might try fully submerging it in IPA

 

[Johnnya101]

Definitely submerge the whole thing. That should get some more goo out. Could be a shorted speaker too, for some reason the Classics have them blown somewhat often. I think you just need to check for continuity or something on it?

 

[mooxitani]

After an overnight bath in alcohol, the sound is pretty much the same. I also measured the resistance of the internal speaker, and it is reading about 60 ohms. What should be my next course of action?

 

[joshc]

Can you please post high res photos of your logicboard?

 

[dochilli]

AFAIK speaker should be 63 Ohm, but I think 60 Ohm will be ok.

 

[mooxitani]

Here are some pictures of the board. I have a feeling I’m going to have to remove and clean under the sound chip to get this working again.

 

[LaPorta]

There's definitely crusty stuff between pins (and maybe under chips) evident at U15 for example. I would suggest at the least getting interdental brushes to scrub between the pins...and possibly even desolder chips if the issue persists.

 

[alectrona2988]

I'm having an issue with my 475 and it making a strange noise on startup. Problem lies in the fact that I used salvage capacitors so I might have to replace those with tantalums or my set of electrolytics I bought on eBay a while back.

 

[Nixontheknight]

I'm having an issue with my 475 and it making a strange noise on startup. Problem lies in the fact that I used salvage capacitors so I might have to replace those with tantalums or my set of electrolytics I bought on eBay a while back.

check the ESR of the capacitors. I replaced my caps on my LC III with tantalum and haven't had a sound issue since