SVT-II non pro schematic 07S519-01

[Lukas2025]

My SVT-II non pro is from 1991 and I have the December 1994 Ampeg update with various update information. The amp makes a loud pop when engaging the EQ on the pre-amp (in and out) and I cannot find the reason. In the 1994 update the pre-amp schematic is 07S519-02. My pc-board says 06A519 01 and the SLM drawing in the 1994 update is an 07-519-01 dated 8-23-88. The 02 schematic is quite different from the 01 pc-board which becomes obvious when checking the pcb tracks.

 

Now my questions:

Has anyone an ...-01 schematic and has anyone an idea where the pop comes from and how to fix it?

 

Thanks Jurgen

[BassmanPaul]

Can't help with the schematics but as a temporary work around drop the volume to zero before engaging the EQ.