Old music centre to audio amplifier

[Edgars]

Hy there!
I inserted this article some time ago in electronics repair section, but nobody answered. So I hope you will help me here....

I have some old parts of the music center (Panasonic SA-AK45) laying around, and I thought if it's possible from these components to create an audio amplifier, so that I can input some audio signal from computer direct to amplifier, and then output to speakers.

I connected transformer with power circuit. It seemed that transformer is working properly, but when measuring voltage on the main chip, there was nothing. Then I shorted out transistor Q505, which drove the relay. And then on the main chip appeared some voltages. After that I tried to input audio signal from computer to the Left and Right channel. Adding some little test speakers I could hear same signals, but the signal was about as strong as the computer gives, there was no amplification. So I don't know what to do next, perhaps there's still some control signals, or maybe there ir some kind of stand by mode. I would like to ask for your help. I added schematics of power circuit, and I have full user guide, so if you need more information - just ask. Thank you!

 

[Fish4Fun]

Edgars.....wow....this is going to be a lot of work to achieve music from a PC......fairly nice, brand new, "plug-n-play" powered speakers from a store can be purchased for << $20.....are you sure you really want to go down this path? If you want to learn about audio amplifiers there are tons of "chips", "kits" and "reference designs" that would be much better supported, potentially more educational, far less time consuming, cheaper and easier.....Re-Purposing highly integrated electronics components and sub-systems is typically best left to "high value" projects....for instance 15 years ago a "military surplus" 3-axis accelerometer might have warranted this kind of effort, but today even it would have near zero value as there are "solutions on a chip" that are virtually "free". Audio amplifiers, no matter how "good they were in their day" are rarely worth attempting to salvage...there are likely some notable exceptions that various audiophiles might point out, but in general audio amplifiers are very mature in design and can be purchased as virtually "stand alone" modules that are easy to implement....especially if your goal is just to "play some music from a PC"....I would suggest you carefully consider the time this project might require and weigh that against the potential reward of making it work.....I am CERTAINLY not suggesting the project can't be successfully completed...i am saying I can't see it being worth the effort....And I can't really see anyone taking this project on to "help" you through it.

Good Luck in whatever you decide!

Fish

 

[Edgars]

Hy! Thanks for the reply.
I realized that I would not be able to use this amplifier, so ordered from ebay a ready-made amplifier board, and will use a transformer from this music center as a power supply. I have pair of these speakers (in picture), so I ordered powerful amp.
However, thanks for advice!