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SA8500 only works on DBT

No just c32 reconnected at that time. And then to ohm out the coloured arrows everything was reconnected hence pad to pad measurements included a component occupying the space, given that I had reconnected everything. I am sorry for the confusion.
 
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OK, so with C16, C24 and C26 disconnected does the resistance still rise slowly to 70k between red and dark blue points?
 
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Ok Tone control switch is on, all pots at TDC, C16 (edited due to typo), C24 and C26 removed from the board, measured at +c16 and -C26 resistance is at 70.3 kohm and gets the very quickly like just a second.
 
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paultlaw said:
View attachment 1729054


Ok Tone control switch is on, all pots at TDC, C16 (edited due to typo), C24 and C26 removed from the board, measured at +c16 and -C26 resistance is at 70.3 kohm and gets the very quickly like just a second.
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That is good, 1 second or so is probably just meter settling time. Leave things uninstalled just the way they are. Next step is to measure those same points, one at a time, but put the black meter lead to chassis ground and measure resistance. It should read way high or even open.
 
merlynski said:
That is good, 1 second or so is probably just meter settling time. Leave things uninstalled just the way they are. Next step is to measure those same points, one at a time, but put the black meter lead to chassis ground and measure resistance. It should read way high or even open.
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Reads open on both points
 
Good, no leakage to ground.
Without reconnecting anything, power up and check for buzz at the + side of C32.
 
paultlaw said:
Ok will do that when i get back from work, what points do i test with C26 reinstalled?
Am i still testing +C32?
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Yes, as the origin of the buzz seem to be right in that area, if we can determine the feedback path for the oscillation we can isolate it..
 
merlynski said:
Yes, as the origin of the buzz seem to be right in that area, if we can determine the feedback path for the oscillation we can isolate it..
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Ok reinstalled C26 and there is no buzz at +C32.

Are we putting C16 in again and repeating the procedure?
 
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Not yet for C16, but please do put C24 back in and check for buzz at C32. If it has buzz lift one end of R28 and recheck.
 
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