Need some help to repair a bad channel on Crown 400CSL power amp. Need a little help where to look. I seem to have a good signal up to C100 but signal after R101 seems bad. I made a couple videos:
Output off speaker terminals.
Signals at C100 input and R201 output.
Here is schematic: https://schematicsforfree.com/files/Audio/Products/Consumer/C/Crown CSL 460.pdf
Any suggestions appreciated.
Output off speaker terminals.
Signals at C100 input and R201 output.
Here is schematic: https://schematicsforfree.com/files/Audio/Products/Consumer/C/Crown CSL 460.pdf
Any suggestions appreciated.
IOC is a loss-of-feedback detector. It just detects excessive input differential voltage, which would result from clipping or overload.
I can see that it is not able to hold a bias point. Now you have to discover what has failed. I would take a DC voltmeter and measure the output voltage. It should be at near zero volts. If it is not then you have a bias problem that you have to trace. You do have your good channel to use as a reference which should make your repair much easier. Most failures happen in the high temperature parts of the output stage or the parts driving the output stage. Don't look at the input circuit until you have verified the output circuit.
Ok, on the bad power amp. I found that diodes D309-D312 have a short across them. I wonder if they are really shorted or something else imposing a short.
Last edited: