Sex C4S problem ....Found

[Mordicai]

It looks like the MJE5731A on the B side of the board is the culprit. It had been checked many times but this time I gave t a good shove and the Left channel started clicking on and off. Resoldered again which helps but if you still give it a good shove it will click on and off. Dont know if thats something I can get at BH, or if I need to try on line, but I think it needs to be replaced. I would like to thank Paul and everyone at BH , for their help. I wonder if this could cause the 150K resistors to overheat??

[Mordicai]

Channel off again. Resoldered the MJE57A31 again, but its not a soldering problem. Some thing seems wrong with the unit, so I will replace it. Could it be a a fine crack in the PC board wiring that open and closes when there is any flex in the board? That might account for the changes in playing the board upside down That's seems like its going to be a bear getting that out and a new one back in

[Paul Birkeland]

The center leg of the MJE5731A is tied to the heatsink of the chip, and consequently it often needs a lot of heat to solder properly.  If pushing on it restores operation, then you should look at all the connections to the board also, as one may be broken or not well soldered.

-PB

[Mordicai]

Ive soldered on it three times, but Ill give it another go Paul. Any idea where I can find a replacement? The chip is discontinued and sold out everywhere I tried.

[bob lennon]

I think MJE5731A was replaced by MJE5731AG which is the lead free version.

[Mordicai]

Thanks Bob, Josh is going to sell some from BH