JBL Graphic Controller SG-520

Description

Rare JBL preamplifier designed to be used with the SE series amplifier and paragon speakers or similar. Cosmetically the preamp is pretty clean, inside and out. There are some dirt spots on the faceplate. The knob covers (metal casing) are loose, but they fit in nicely so I suspect the original glue they used have dried out and lost the grip.
The preamp has output, sound is clean and without distortion. I tested the Aux input only (did not test the rest) and it has clean sound. The equalizer portion works, same as balance control and loudness switch. Here is the problem that I found during testing:
- The Stereo mode only has output on one side, when I put it to rev S, both channel has output. This maybe loose wiring or simply need deoxit.
- Using rev S, one channel seem to be louder than the other, and it doesn't change with input switch so definitely the preamp will need to be serviced.
Its a vintage preamp, it will need to be serviced to bring it back to 100% operation. It is sold FOR PARTS OR REPAIR, and no return accepted. I have stated all the problems I found during testing, so ask any questions you want before purchase. Audition is available in Falls Church, VA.