We went down this path because you said right channel was fine until you swapped the drivers from R to L channel and then the symptom moved with the drivers, left became good and right became bad.
Measure the right channel collector to emitter voltage at the pads on the control board.
We went down this path because you said right channel was fine until you swapped the drivers from R to L channel and then the symptom moved with the drivers, left became good and right became bad.
Measure the right channel collector to emitter voltage at the pads on the control board.
yes, it did....then when i thought we were making progress....the right bias dropped to 10...and has been there ever since....as if a part just went bad as we were working on it...and did not move back to the left side when the transistors made their way back to the original positions....
We went down this path because you said right channel was fine until you swapped the drivers from R to L channel and then the symptom moved with the drivers, left became good and right became bad.
Measure the right channel collector to emitter voltage at the pads on the control board.
85.7 volts at r19
q7 test good and equal to left q7
q8 test good...with a slight needle movement in reverse ...q8 left reacted the same...slight needle movement in reverse...
r39 measured 199 ohms
all tests done in circuit...
85.7 volts at r19
q7 test good and equal to left q7
q8 test good...with a slight needle movement in reverse ...q8 left reacted the same...slight needle movement in reverse...
r39 measured 199 ohms
all tests done in circuit...
i did change q5 and q8....but on the left channel when i had dc on the ouputs....
you advised me a bad q8 had no other route except to rail voltage...
and q5 was designed to protect q8, which it failed miserably at...
i memory serves me...
yes sir..
r8 is the pot for offset....x 2
r14 is the pot for bias....x 2
service manual says r20...but that is an error since r20 does not exist on the 400c
yes sir..
r8 is the pot for offset....x 2
r14 is the pot for bias....x 2
service manual says r20...but that is an error since r20 does not exist on the 400c
sorry....i guess i did not understand...my apologies
e to c on left channel plus or minus 2.3v depending on polarity of leads to dvm
e to c on right channel plus or minus 1.3v depending on polarity of leads to dvm
sorry....i guess i did not understand...my apologies
e to c on left channel plus or minus 2.3v depending on polarity of leads to dvm
e to c on right channel plus or minus 1.3v depending on polarity of leads to dvm
i did change q5 and q8....but on the left channel when i had dc on the ouputs....
you advised me a bad q8 had no other route except to rail voltage...
and q5 was designed to protect q8, which it failed miserably at...
i memory serves me...
