No sound Classic II boards

[captjon320]

All,

I have 4 Mac Classic II that I am working on. All have been recapped and run through ultrasonic cleaner. I have 1 fully functioning logic board. I have used that logic board to check all the other analog boards/speakers. All speakers/screens function with this board so I know it is a logic board problem.

I have removed, cleaned and reinstalled U1, U2 and U4 on the first four pictures. No help, still no sound and board boots to desktop fine.

The next logic board I have not removed any chips and it shows screen(s) as pictured (remaining 6 pictures) when booted with no sound.

The third board used to have sound after recapping 3 years ago and now no sound, it is not pictured and getting an IPA bath.

I realize this is difficult to diagnose and probably a bad trace somewhere and out of my skill set. If anyone has any other suggestions, I’m open to any.

 

[bibilit]

Hi, not easy to help, but sound is generated by U4 (DFAC) if you have already swapped chips, not your issue here.
Moreover, this chip is almost never bad.

Probably a bad or broken trace in the capacitor area.

Keep in mind that the bad trace can also be located in the other side of the board.

 

[captjon320]

Thanks, I didn't sway the chip rather just took it off and cleaned and reinstalled. I agree this chip almost never "goes bad" rather it is very dirty most of the time. Traces are my nemesis and I can never seem to track them down correctly as it is not in my skill set. +1 on the back side of the board as well. Thanks for your input.

Do you know what would cause the distorted screen on the 2nd board?

 

[bibilit]

Hi, hard to say concerning the board, can be the Egret chip.

I don’t know for sure, but maybe spotted some bad traces, one seem broken.

 

[imactheknife]

I have almost always have had to pull off the sound and egret on those boards due to cap leakage. I have had broken traces, or legs turn to powder so needed to cut into the actual chip etc etc.

 

[captjon320]

Thanks all, I pulled both the sound and egret chips and found broken traces under.

I appreciate it.

 

[imactheknife]

Thanks all, I pulled both the sound and egret chips and found broken traces under.

I appreciate it.

Excellent hope it resolves the issues!

 

[smrieck511]

Thanks all, I pulled both the sound and egret chips and found broken traces under.

I appreciate it.

Hi, I have a Classic II with sound issues, so I'm curious to know if/how you resolved this? Thanks.

 

[imactheknife]

Hi, I have a Classic II with sound issues, so I'm curious to know if/how you resolved this? Thanks.

Usually recapping will help most things, but getting rid of any extra cap leakage is important. So that makes anything surrounding leaking caps a target. The egret chip and sound chips usually get it good from cap juice. So in my experience i normally have to pull sound chip off and sometimes egret chip as well. Most likey just dirty pads/ feet but sometimes broken traces / rotten vias too. Recap is only part of the fix in these ones

 

[smrieck511]

Thanks. Which one is the egret chip?

 

[imactheknife]

Thanks. Which one is the egret chip?

One is sound, other one is egret. Any blue/ green corrosion on legs?

 

[smrieck511]

thanks ..yes the egret chip is the most corroded on the board. I've been working on it but it's still not looking great.

 

[imactheknife]

thanks ..yes the egret chip is the most corroded on the board. I've been working on it but it's still not looking great.

thanks ..yes the egret chip is the most corroded on the board. I've been working on it but it's still not looking great.

Is the board working just sound issues? Or is the whole thing not working properly? If just sound i would focus on the sound chip. Has anything been recapped?

 

[smrieck511]

Fixed it! C9 had a broken trace. Thanks for your help!