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RE: Yamaha CA -810

Posted by ESDI-80 (A) on July 14, 2014 at 11:59:03

In Reply to: Yamaha CA -810 posted by broadband2002@hotmail.com on July 13, 2014 at 12:54:50:

First:

One thing to check is to trace where the speaker outputs tie from the amp boards / circuit to the relay circuit. The relay will not engage if you have DC on the speaker outputs. If the DC offset is off enough, the relay will not engage. The service manual will tell you where to set this.

Second:

Another thing to try is to remove the output transistors and power the amp up. I've done this in the past to determine if I indeed had blown output transistors. Just make sure to note on the location of each transistor. You don't want to reinstall them in reverse, NPN into a PNP and vise versa. Also, don't mix the pairs up for each channel. Output transistors are matched.

If your relay clicks in with the output transistors removed, then best bet is you have a shorted transistor. I've seen the fuse not blow when an output transistor shorted. They tend to take out resistors down stream in the circuit or blow traces off the circuit boards.

Hopefully this will help. :-)

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