First thanks for reply. I am electronic hobbiest and I have a preety good equipment (dont have a osciloscope). It means I have a digital meter a couple solder gun, vacum pump and I can change parts because I made some equipment for me. BTW I a old on thi forum but I must change username because my e-mail was corrupted and I change it. One more time thanks for reply
Hi, Dukanita.
Unfortunately I can no longer find the 222 schematic on the internet but do I recall the the schematics being similar to the 22 - only with a few extra passive components.
I suspect Q2 or I4, more likely I4 as it's quite static sensitives.
First measure the control current from pin 1 of Q2 (above I4, which is the left-most CA3280). Confirm that the current is fluctuating. Compare with pin 1 of Q4 (from the bass channel) if you'd like. If you suspect that's fine, next check the voltage of I4's first output, pin 13- this voltage goes through a unity buffer that drives the treble LED.
If I4 proves to be failing, you can replace it with the modern part AS3280.
Unfortunately I can no longer find the 222 schematic on the internet but do I recall the the schematics being similar to the 22 - only with a few extra passive components.
I suspect Q2 or I4, more likely I4 as it's quite static sensitives.
First measure the control current from pin 1 of Q2 (above I4, which is the left-most CA3280). Confirm that the current is fluctuating. Compare with pin 1 of Q4 (from the bass channel) if you'd like. If you suspect that's fine, next check the voltage of I4's first output, pin 13- this voltage goes through a unity buffer that drives the treble LED.
If I4 proves to be failing, you can replace it with the modern part AS3280.
Someone who is reading this thread, informed me, that some of you is seeking a CA3280 (Transconductance amplifier). I have 5 of them (Intersil, I believe), NOS. Never used, never taken out of the foam packaging. In case the person is interested. I didn't follow this thread, so bear with me if I'm just chiming in here.