It has 520mv (side towards power supply) and 110mv on other side (closer to the op amp). I also notice the output voltage was slowly very slowly increasing when no load was present/attached. Went from 1.5vAC to 2.5vAC.
Post the AC voltage on the following points.
High voltage side of R115 (to confirm that nothing has changed)?
U14 pins 1, 7, 8 14?
High voltage side of R115 (to confirm that nothing has changed)?
U14 pins 1, 7, 8 14?
AC on speaker output is at 1.77 (slowly rising)
R115 high side is 460mv
U14
1) 50mv
7) 48.7mv
8) 147mv
14) 163mv
R115 high side is 460mv
U14
1) 50mv
7) 48.7mv
8) 147mv
14) 163mv
Signal is 125hz sine wave 1.0vAC RMS. Got higher output on the speakers (3.8vAC)
R115 480mv
1) 111mv
7) 110mv
8) 285mv
14) 284mv
R115 480mv
1) 111mv
7) 110mv
8) 285mv
14) 284mv
R101
reads 22k (probes/leads dont effect read out)
R102
reads 10k with leads switch it read 20k, guessing something to do with a capacitor polarity that is parallel with resistor? This is only after if I read the resistor upon turning amplifier off, after a minute it read 20k with leads/probes either way.
Will grab something to eat, will be back in an hour or two, thanks Perry for all your help.
reads 22k (probes/leads dont effect read out)
R102
reads 10k with leads switch it read 20k, guessing something to do with a capacitor polarity that is parallel with resistor? This is only after if I read the resistor upon turning amplifier off, after a minute it read 20k with leads/probes either way.
Will grab something to eat, will be back in an hour or two, thanks Perry for all your help.
Don’t know but both pin 1 and 3 of U11 are 0.9m. I am removing the board from sink and will replace the smd caps and check the large capacitors. Seems like the issue is in the preamp section, hopefully I can track it down. I really appreciate you pointing me in the right direction Perry.
Is the gain control fully clockwise? If the voltage on pin 14 is nearly 900mv, the same should be on R115.
Yes the gain is fully clockwise; it does seem to be effectively operational (as it lowers the very little output it has on speaker terminal accordingly to the gain).
Pin 14 of U11 goes to R100 (which read correctly) then goes to gain pot and comes back (Appears to) to a SMD capacitor C109 then goes to R115.
Checking C109 it doesn’t read any capacitance. C109 read 460nf and has esr of 600ohm, safe to assume this may be part of the issue (hopefully the whole problem, fingers crossed)🙄
Pin 14 of U11 goes to R100 (which read correctly) then goes to gain pot and comes back (Appears to) to a SMD capacitor C109 then goes to R115.
Checking C109 it doesn’t read any capacitance. C109 read 460nf and has esr of 600ohm, safe to assume this may be part of the issue (hopefully the whole problem, fingers crossed)🙄
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Well I pulled 5 SMD caps that were in the preamp/crossover/Remote section that read bad on my LCR meter, I also pulled a couple of the leaded large filter caps and the non-polar to test (which tested good). I used leaded for just testing purposes and powered up. YIKES I forgot the gain was set fully CW and was getting a weird buzzing noise in the output filter section, lol, measured the output and had around 170vAC (Yes severely clipping). Adjusted the gain to get around 110vAC prior to clipping without load.
I would like to thank Perry and goviboo (helped me as well and pointed out the bad caps on these amps).
I would like to thank Perry and goviboo (helped me as well and pointed out the bad caps on these amps).