i´ve a similar problem . And the problem was in R88 & R90. Are you test the R88,R90,Q12,Q13??Hi all
So after fixing one 212r I find myself with a second with a more curious symptom. The amp works but breaks up in an almost bitcrushed, digital way on the fadeout of chords, and sounds generally very unwell.
It's in the power amp section, the preamp going to another amp sounds fine, and the problem remains the same sending a preamplified signal from another 212r to the power amp input.
The board looks clean, I've cleaned all jacks and pots, the power resistors that are often faulty on these amps are securely soldered (as far as I can tell) and in spec. The board looks generally good and connections check out wherever there's any question over them. The big caps are in spec from a quick test in circuit with an ESR meter.
The 4 big transistors have only been checked in circuit, but they show 0.6v voltage drop in most directions, not open in some as expected, but I've ONLY tested these in circuit and haven't checked the schematic properly to see if this is normal yet (in truth, I'm still learning to see that part of signal flow on a schematic, haven't worked on many transistor amps) so I don't know if I'm reading that voltage drop because of other transistors in the circuit. I can take them out and test but wanted to get some advice first as they are connected in a fairly robust manner that I didn't want to mess with without input from people here!
So something is out, but this type of symptom is new to me, I'm probably more comfortable dealing with 'no sound', 'loud hum', 'intermittent sound' etc.
I can start taking out things in the power circuit and testing but I really would be shotgun-approaching it at this stage, so wanted to see if the sound it makes (recording attached) points to any rough area I should start with!
All the best, and thanks to anyone who would like to help!