Pioneer SX-850 Power Amp Board; Remove & Recap or No?

Juanbanzai

Juanbanzai

Active Member
Hi Guys,

I had an earlier post where there was a low output problem being caused by two transistors being installed incorrectly and I also had a cap installed backward on the tone amp due to the silk screening not labeled correctly. All the issues were rectified and the unit sounds incredible. I've got more power coming out of this thing and I could ever want.

However... I haven't touched the power amp board yet and I have the components necessary to recap it and replace the trimmers.

The first problem I have it actually getting the board out of the chassis. I'm not a big fan of pulling the sockets off the final output transistors in order to free the wires up, and I don't see how loosening up the heat sink and folding it back is going to help me get to the back of the board. As I'm sure you're aware, there are wires along the top and bottom of the board, and for the life of me, I can't find a way to get it out without major surgery. The wires are very tight.

So... should I leave well enough alone... perform a bias adjustment if needed, and enjoy? Or should I recap the board? And if I go that route, how the heck do you get it out to work on it? Any potential danger with leaving it alone now that everything else has been recapped including the power supply board?

Thanks.

Aaron
 
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i did one about 4 yrs ago. i dont recall exactly how, but i DIDNT have to remove the amp board.you do want to minimize the flopping back and forth to get at different components. this keeps you from breaking the wire wraps. if you do its not the end of the world as we know it,remove the broken wrap from the pin and solder it.
 
Yup, just unscrew the heatsink, fold it out, and remove the metal plate behind the amp board. Voila. Easy.

Replace the uni-watts!!!!! I've had several 850's fail because of them. KSC3503 and KSA1381.
I'm assuming you're replacing the input pairs with KSA992 as well.
 
Super Noob said:
You can do it without removing the wires and outputs.... not easy but not hard.


13:00
Click to expand...
Hey Super Noob,

Thanks for posting the video. I was searching all night for just the instructions you provided but couldn't find anything. It's brilliant and just what I needed. Going to attempt the recap of the board now.
 
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