Crown XLS 202 Amplifier Repair – Part 5

I found out you can flip the main PC board (saving me from removing all PSU and ribbon cable wires)!  This is very convenient and just made this repair task so much easier and faster.

pcbflip

These are the locations of the Channel 2 Power Transistors.

channel2

Doing some resistance testing using a multimeter, I confirmed that one of the NPN transistor was shorted (due to it’s very low reading).  But since we’re already here, I decided to just replace ALL Power Transistors of the affected channel. The NPN/PNP power transistors were only $4.60 each at Mouser.com, so it’s better to replace them all now while I have the PCB right in front of me.

A Hakko Desoldering gun is a godsend for this job. I just use the desoldering gun to remove the Power Transistors soldered to the board, then unscrewed the heatsink from the board. powertransistors

Heatsink successfully removed from board. Now, it’s just a matter of unscrewing the TO-3 transistors, cleaning the heatsink, applying some fresh thermal compound, and installing new transistors back. mj15025

So after replacing all Power Transistors in Channel 2 (again, only (1) NPN transistor was bad, but I just decided to replaced them all and give it a “fresh start”), put everything back together, and power up the amp.

Fingers crossed…. the amplifier stayed on, and didn’t shut down! No more FAULT lights. Yay! The amplifier seems fixed.

ampfixed

In my excitement, I didn’t bother connecting it to a signal generator and oscilloscope, I just went ahead and connected it to my speakers and fed it some audio signal.

YES! It’s fixed.

The final step is replacing all the tiewraps I cut, making sure all the cables and wires are secure inside the amp, double check all screws are tight, and replaced the cover shut.  Done.

Thanks for reading!

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