There is certainly more than one way to proceed but all of these require methodical actions and discipline 🙂
I will keep going even if I never figure it out. It is already a write off for me, either I get it working or it explodes
.Bit of an update. I had written off the amplifier and instead decided to use it for parts if I ever found a defective device. Well that day was today (yesterday). I got a ta-n80es that was 'working', however the left channel was slightly lower volume than the right, the right channel didn't measure any bias. The condition of the front panel was rough and it was also missing the original wooden side panels, a prime candidate for my needs basically.
The amplifier has had several repairs already and quite a few traces are gone. One of the voltage regulation parts on the mainboard (b IIRC?) was repaired using a weird integrated circuit that was basically two transistors in one. My parts amp still had this segment in original condition so I restored the traces and put back the original transistors and bridge connectors. I also replaced all the emitor resistors as I still had them left over from my previous repair attempts and they had already been replaced with two different types of resistors. The right transistor that is on the heatsink that goes to the mainboard a (the one that has the adjustments) had cracks in the legs and ended up breaking off. I replaced it with the one that was in my parts device. The speaker connector board had a loose coil, and was missing one set of the speaker connectors, the remaining pair being not original. I replaced this with my parts one as well. I also replaced the volume knobs as the one in the amp had been bypassed to act as a full range one rather than the normal -20db to 0 db. This can easily be repaired by removing the wire modifications but replacing them was even easier.
my trace repair on the voltage regulation part (before solder mask).
After all that, as well as some general solder joint repair (the previous repair person wasn't very meticulous with their soldering job to say the least), the bias on the right channel was still not working. I had already checked the potentiometer and that seemed to measure fine but after another hour or so of trouble shooting I decided to just redo the joints anyhow and luckily that ended up fixing the issue. I calibrated it and both the bias and the offset stayed steady at their calibrated values. I have listened to it in my setup for about 30 minutes and it sounded fantastic.
Thank you to everyone that helped me on this thread. While the initial device wasn't repaired, I definitely would not have been able to repair this one without the experience (and parts) I gained from the many hours I spent on the first one.
The amplifier has had several repairs already and quite a few traces are gone. One of the voltage regulation parts on the mainboard (b IIRC?) was repaired using a weird integrated circuit that was basically two transistors in one. My parts amp still had this segment in original condition so I restored the traces and put back the original transistors and bridge connectors. I also replaced all the emitor resistors as I still had them left over from my previous repair attempts and they had already been replaced with two different types of resistors. The right transistor that is on the heatsink that goes to the mainboard a (the one that has the adjustments) had cracks in the legs and ended up breaking off. I replaced it with the one that was in my parts device. The speaker connector board had a loose coil, and was missing one set of the speaker connectors, the remaining pair being not original. I replaced this with my parts one as well. I also replaced the volume knobs as the one in the amp had been bypassed to act as a full range one rather than the normal -20db to 0 db. This can easily be repaired by removing the wire modifications but replacing them was even easier.
my trace repair on the voltage regulation part (before solder mask).
After all that, as well as some general solder joint repair (the previous repair person wasn't very meticulous with their soldering job to say the least), the bias on the right channel was still not working. I had already checked the potentiometer and that seemed to measure fine but after another hour or so of trouble shooting I decided to just redo the joints anyhow and luckily that ended up fixing the issue. I calibrated it and both the bias and the offset stayed steady at their calibrated values. I have listened to it in my setup for about 30 minutes and it sounded fantastic.
Thank you to everyone that helped me on this thread. While the initial device wasn't repaired, I definitely would not have been able to repair this one without the experience (and parts) I gained from the many hours I spent on the first one.
