Recent content by Schmidlapper

You did well and learned much along the way, the most important being that you can. Nice work.

Ok they share the same circuit. The SX-780 has a much better service manual than the SX-790, both on HiFi Engine.

This is a good point, also the balance circuit could be a factor alternatively. This is where a scope would be helpful.

I thought this was a SX-790?

Ok, if you have gotten them both to null then the variance is not likely an issue, maybe an effect of the issue. The schematic shows many nominal voltages you can check, the other channel mirrors it. Continue looking for differing values from on the schematic and the good channel and write down...

I'm looking at R237 and R238, both 36K ohms, the one side indicates a nominal value of 17.1v on the schematic, looking at the photo I am assuming that is where you are seeing the differing values you measured. When the manual has you adjust for the null, is it using VR5 and VR6? If so where do...

If I'm transferring that pic to the schematic correctly and those voltages are set with VR5 and VR6, the voltage closest to -17.1 should be the working channel. Can you verify?

Maybe you already did this, but in my ST-70 rebuild I had so many squirrely issues until I heeded the recommendation of someone on here by replacing all the old original tube sockets. The old plating was so worn, it would clean up briefly only to quickly corrode again. I had random noises...

I’ve purchased eBay electronics that have came with all sorts of dead bugs inside, never saw a fried one though. Reminds me of the story on how the computing term “bug in the system” came about. Cotton swabs would be useful as well when needing to remove that much unwanted material without...

Glad to hear your new cable has solved the input issue. It appears you have one working channel, and one degraded channel. The good news is that with one good channel you have the perfect example to compare voltage readings against.

Thanks for that. Your phones measurement of .98 Vpp provides approx .350mV RMS, which should be more than sufficient for the SX-780 based upon manufacturer stated input sensitivity of 150 mV. I have been hoping the OP doesn't have an output power issue instead. Without knowing the actual input...

Excellent! Where there separate adjustments for each individual meter on yours, or a common one?

I find two details to be interesting, The first is found in the original post of the OP, and RTally later describes it well in post #44. If the output is indeed only reading between 8 to 10 volts, then mid scale on the meters would not necessarily be inaccurate. Second there are two meters...

There is an old story about a dam that has developed a problem that no one has been able to resolve. So they call in a fellow who is considered a specialist to diagnose the dam. After a spell he presents a report showing a 75 cent part is required to correct the problem, and a bill for $2000.75...

i spoke to the load quite plainly in my prior posts, but maybe you weren't commenting to me specifically. The OP doesn't delve much into their set up or procedures.