Amiga 3000 audio repair

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alamone
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Joined: Wed Mar 09, 2011 10:32 pm

Amiga 3000 audio repair

Post by alamone »

Hey, if anyone out there is knowledgeable about Amiga 3000 repair,
I have an Amiga 3000 whose sound no longer works. It previously had the
corroding battery problem but the corrosion damage was repaired.
It was working fine until about a week ago when the sound suddenly cut out.
The sound does still output but it's very low volume and distorted.

I already tried replacing the op-amp and capacitors and nothing changed.
I also tried swapping in a known working power supply and that did not help.
At this point not sure how to fix it; any pointers or suggestions for repair services
would be appreciated; I'm located in the US. Thanks!
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CkRtech
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Location: Seattle, WA

Re: Amiga 3000 audio repair

Post by CkRtech »

You know who is really knowledgeable about Amiga repair? This guy: https://www.youtube.com/user/RetroGameModz
alamone
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Re: Amiga 3000 audio repair

Post by alamone »

Already skimmed through that guy's videos for the A4000, he just did the usual op-amp replacement...
Also, the A3000 has a different audio circuit layout compared to the A4000.
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CkRtech
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Re: Amiga 3000 audio repair

Post by CkRtech »

Well, I was thinking you could contact him.
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system11
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Re: Amiga 3000 audio repair

Post by system11 »

http://www.amigawiki.de/dnl/schematics/A3000.pdf

Affecting both channels? Page 9 - potentially the filter circuit, or voltage to the op-amp.
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alamone
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Re: Amiga 3000 audio repair

Post by alamone »

Affects both channels. I think the voltage to the opamp is suspect.
The -12V line is okay but the +12V line measures around -3V.
How can I fix this?
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system11
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Re: Amiga 3000 audio repair

Post by system11 »

Page 4, C169, C170, C177, D192.

I'd check if you have 12v both sides of D192 and pin 15 on the power connector.
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alamone
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Re: Amiga 3000 audio repair

Post by alamone »

I checked both sides of D192 and it reads +12V more or less.
Also pin 15 of the power connector is outputting +12V just fine, and the SCSI HDD works.

Edit: Fixed it! Jumped pin 4 of the TL084CN to the output of D192 and now it sounds great.
I guess somewhere in the circuit the +12V voltage went bad for the sound circuit.
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