JBL SRX 828SP preamp problem?

[opacheco]

Hi there, I am searching for any idea with a rare problem that I have with a pair of SRX 828SP. The SRX 828SP doesn’t increase its volume although the gain potentimeter is the maximum value +12dB showing in its screen.

To me this trouble look like preamp board problem (no amp section, the power amp is ok because I tested with a preamp board assy only from another good one SRX 828SP unit!). I have attached the pic of the preamp board that I think the problem is.

I connected this SRX 828SP to my laptop pc with HiQnet JBL software and here I can send the pink noise normally but when I send the audio signal doesn’t see in the bar level indicator in the control software!!

I have changed the two input Opamps M33078 (U1 and U3) for new ones but the problem is still there.

Do someone have the schematic of this sub bass JBL unit?

Does anyone have had this same problem before?

In the worst case I would have to buy two cards that according to JBL are part number 5044210-04 PCB,ASY,Input,Sub,AV, but I don’t find any seller of them.

Thanks
opacheco

 

[opacheco]

Any idea?
opacheco

 

[scott2000]

Maybe there's another manufacturer that has a comparable product and who supplies schematics? Mackie for example? Could be some clues? Or not....

 

[opacheco]

Maybe there's another manufacturer that has a comparable product and who supplies schematics? Mackie for example? Could be some clues? Or not....

Ok thanks for your comments but look like that is rare trouble with these JBL active subs and no common or unknow failure for here!!…i would like to know if do someone have had this problems before??

Thanks
opacheco