PB10 Loud Hum and Crackle- LED Lights mixed Red/Green

replace C42. easy fix. ordered the new capacitor from amazon (100uf 35v)

An answer I given to another post.

While walking in my neighborhood, a JBL PB10 was thrown away for garbage pickup. I can use another subwoofer so I brought the orphan JBL PB10 home. It has the same problem. I am a retired electrical engineer. If I get the schematic, I might be able to fix it. I indeed found the service manual from the following URL. It turned out you can fix the problem by just cutting off one pin of a transistor. I don't think most people are interested in theory, but just a brief and then the solution.

JBL PB10 service manual
http://akdatabase.org/AKview/albums/userpics/10004/JBL%20PB10%20Service.pdf

The manual is for the version 6.3 circuit board. I have a version 7.3. But, they are the same for my purposes. The LED lights are controlled by an integration circuit shown on page 28. When the signal at the low level line input is smaller than 5mv rms, the LED lights are set to red. In the meanwhile, the integration circuit set the Q1 junction FET transistor to on so the SIG signal is grounded to subdue any nuisance of noises (no sound produced). When there is a significant signal at the line input, the integration circuit set the LED light to green and turns off the Q1 transistor so the SIG signal can be freely amplified by the AIM power amplifier.When the integration circuit malfunctions, most probably C42 fails (could also be C40 and/or C41). I don't have any capacitors at hand to fix so I just cut off one of the three pins in the Q1 transistor to disable it from grounding the SIG signal. Q1 location could be found on page 26. The pin to cut off is one of the two outer pins. It is the one further away from C40. Once you cut the pin off, the sound will be back. But the LED lights remain red.

As long as its not blowing the fuse it can be saved - look for Edwards Electronics - Ebay - We fix them . Thanks.

You blew your woofer or shorted the output transistor in your amp.

Service manuals: http://manuals.harman.com/JBL/HOM/Service%20Manual/PB10%20sm.pdf
http://manuals.harman.com/JBL/HOM/Service%20Manual/PB12%20sm.pdf

My ClassD module shorted out (buzzing sound/blown fuse) and not availabled any more so this is what I did: http://s807.photobucket.com/albums/yy352/budm/JBL%20PB-12%20mod/
I would suggest to buy new one.

Here are the service manuals, you may what to read the service bulletin section. Most common failure in the PB10/12 is the blown ClassD amp module which you cannot get it anymore. This is how I fixed my: http://s807.photobucket.com/albums/yy352/budm/JBL%20PB-12%20mod/

i have the same problem. don't as yet have a solution

It can be bad filter caps, read the service manuals here: http://manuals.harman.com/JBL/HOM/Service%20Manual/PB10%20sm.pdf
http://manuals.harman.com/JBL/HOM/Service%20Manual/PB12%20sm.pdf

Or bad power amp module, take the voltage reading per SM, I mod my, http://s807.photobucket.com/albums/yy352/budm/JBL%20PB-12%20mod/

More likely to have bad power amp module, service manuals: http://manuals.harman.com/JBL/HOM/Service%20Manual/PB10%20sm.pdf
http://manuals.harman.com/JBL/HOM/Service%20Manual/PB12%20sm.pdf

I mod my, http://s807.photobucket.com/albums/yy352/budm/JBL%20PB-12%20mod/

More likely to be the Class D power amp module, but you should look through the service manual to make sure all the parts are installed correctly. My PB10 AMP module went out and you cannot get one anymore.
http://manuals.harman.com/JBL/HOM/Service%20Manual/PB10%20sm.pdf