Thanks! Thanks! Thanks! Solved!!
LM4562 finally worked ok in the "bad" channel bypassing both R100 and R101. Haven´t time today to try resoldering the caps. I´ll try at night.
This happens just in one channel probably because once there is large current flowing into one opamp (there's always one opamp first due to very minor differences in wiring resistances, parts tolerances etc.) the positive supply sags a bit and thus protecting the other channel. Now we've fixed one channel, so the other ain't protected any more.
One point here, the main swtich goes to the good channel (directly) and to the bad channel switch. So to start the "bad" channel, by force had to switch the good channel before, but not viceversa, when switched the good channel, it was alone working. So seems that istead of helping one to the other, maybe the result was an increased time to supply pin 8, I think.
Likely this will also make the NSC opamps work--probably their linear common-mode voltage is exceeded because of the voltage drop across R100.
Didn´t understand that, but they work now. Will have to study. It´s nice knowing.
there's not much point typing here for days
Your efforts gived result, and saved me hours of frustration and money of opamps dead. I would like to compensate your typing time if I can.
I have just two doubts, last two doubts I promise:
1- Regarding the not centered PGN, have any influence in the DC Bias adjustment made by RV1, RV2? Any influence regarding sound performance, or is it ok like it is?
2- The extra big caps I put on the supply rails, are 4700u (like C114-C115 position) but they are "before" the power switch. I put them because measuring with a scope the supply rails, found some AC present just when singing very hard in the mic, maybe regarding the batteries internal impedance. I thought about the batteries couldn´t be fast enough to supply the current demanded by the preamp in short times. After put the caps, the AC disappeared, and so they seem absorve that current flaws.
Question is, should they be better after the main switch? If so, should they make the supply rise slow enough as you told about mains powered supplies? (now are always charged, conected directly to the batts)
In general, if my supply could be improved, I should like to know what could be done, without using regulators, what they have a lot of consumption for my batteries.
Best regards,