6290 amplifier mods on Pcb

[Jorre Pulle]

Hello to all,
I have 6290 amplifiers and some of them have extra components soldered on the Pcb.
It looks like a later mod,some have a small pcb soldered containing a transistor and some resistors and others just a electroytic cap and some resistors.
Some amps do not have any mod installed.
Placement of the extra stuff seems to be at location of R13&R14 and R7&R6.
Does anybody know if this is a official Jbl mod and does someone have some info on that?
Many thanks in advance.

E-mail : [email protected]

[stephane RAME]

The schematic

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/JBL-6290%20manual.pdf

Stéphane

[Jorre Pulle]

I am not looking for the schematic,i know it by heart.
It's the different mods on the Pcb i am interested in,like my thread stated...

[Eaulive]

That doesn't look too original to me... looks like somebody used replacement transistors that were not the same and tried to compensate with some kind of circuit.

Kind of trying to replace older power fets with newer MOSfets