68kMLA Classic Interface

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LC II sound chip needed

Posted by: theretroprojects on 2020-03-17 13:51:35 Hi mac'rs I recently aquired an LC II with bad cap, the machine wouldn't boot and made stage sounds from the speaker, I cleaned up the juice and then the system booted with start-up sound, great. So I recapped and it went well, very please it still booted, however, I get no sound now. From reading on here the general consensus is that the sound chip has failed, I believe its the UB10 DFAC. So I'm looking for a replacement chip, does anyone know where I might get one please, I've taken great care and time restoring this machine and now totally gutted this has happened. I would love to get it full working again if anyone can help. Thanks All

Posted by: theretroprojects on 2020-03-19 10:38:46 Does anyone know if a psu can cause sound issue? I haven't recapped that yet.

Posted by: Bolle on 2020-03-19 10:48:54 It’s possible you damaged a trace around the sound chip when recapping it. Have seen that happen very often. Start with checking the connections between all your new caps and wherever the other end goes according to the schematics. Especially those caps in the audio section. I really only had a dead soundchip in the countless boards I had on my desk now. If the soundchip was completely dead your machine would most probably not boot because the soundchip also controls the main reset line.

Posted by: theretroprojects on 2020-03-28 17:01:25 So i checked everything I could, all the caps + and - sides can be traced to another point with continuity, but still no sound. I decided to remove all the caps around the sound ic and power it on (not knowing what might happen), it still powers on and boots, but still no sound, however, I do hear a quick click sound from the speaker when I power on now, didn't notice that before removing the caps. Does anyone know which caps are required for the sound to work? Looking at the schematics, pin10 from UB10 is audio-out, following this path i can only see, C10, C11 and C12, connected to the output circuit, most of the other caps are connected to the UB10 IC so could this be audio-in?

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