davbucci, 5 months ago

There was no audio output from the #turntable. It seemed that the culprit was the IC amplifier, an unobtanium SBF3B. From the schematic it looked like a dual opamp with a voltage divider and some compensation inputs. I tried to adapt a TL082 and it seems to work! #electronics

My wirewrapped modern op amp to substitute the original one.
The wiring exposed.
The blob of wires in the circuit.

davbucci, 5 months ago

I still had to redo a solder joint on one of the loudspeaker that failed. Now everything works, but one of the channels has a volume that is much less than the other one. I suspect the capacitors, now.

davbucci, 5 months ago

It seems that the second channel that was working worse is slowly coming back to life. Some capacitors are slowly reforming themselves?

davbucci, 5 months ago

This is the schematic of the replacement of the #SBF3B chip with a TL082. I did not care about the additional feedback path provided for the compensation as the TL082 should have a sufficient phase margin by itself.

davbucci, 5 months ago

I will listen to some music with the Philips #turntable to test it but now everything seems ok. My mother-in-law will be happy!

davbucci, 5 months ago

@janbeta given our recent discussion about turntables you may like this repair.

janbeta, 5 months ago

@davbucci Wow, nice job replacing that broken amplifier ic! Also, the world should return to including schematics with devices. I know Philips did it for most stuff up until the late 80s at least. More civilized times (at least regarding the right to repair). 👍

davbucci, 5 months ago

@janbeta thank you! Indeed, giving appropriate repair information (including software) should be made mandatory.

janbeta, 5 months ago

@davbucci Hope the right to repair is going to get much better in the future. Would be great for the planet and for repair shops and hobbyists alike. :)