Repairing JBL Amp With Isues on 2 Outputs


Postby jimmies » Thu Aug 04, 2016 12:53 pm

I have a JBL amp which is working BUT there's something wrong with 2 of the outputs.
Front left output just buzzes and front right produces no sound at all.
I opened it yesterday and just from looking at the board I see nothing wrong with it so I'm not sure where to go from there.
I'm also a noob in electronics but willing to learn a lot!
I attached pics of both sides of the board (these are only until I charge my camera and learn how to take better pictures). Marked with red are those outputs.

http://i.imgur.com/eIRBfE6.jpg
http://i.imgur.com/CdHdRoo.jpg
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Postby jimmies » Wed Aug 10, 2016 2:05 pm

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Postby ericmark » Wed Aug 10, 2016 10:08 pm

Often the best repair system is to replace. I worked on some welding machines, these had electronic boards to control the FET's or Thyristers, can't remember which, and the board had 4 Opamp (741) which cost pence. The whole board cost around £200 service exchange.

So we would remove the opamp, fit 4 IC holders, insert 4 new opamps and see if it worked, 9 times out of 10 it did work, on the 10'th we sent back for service exchange. We had no equipment to test, we just realised the opamp was the weak link.

Once one passes that stab in the dark approach, then you start to look at expensive test equipment. With 100's of welding machines it was worth our while doing the quick on site repair. But you can also have the problem where one component fails because another component has also failed so replacing components can prove expensive.

I have not opened your pictures they don't auto show and I am always worried about virus in photos, but did see what seemed to be the same post on another forum. And it seemed as if the board had surface mount components. Although you can change surface mount components it is not easy, and I would not expect you to succeed, so likely changing components in your case would be throwing good money after bad.
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