2023 Mojotone BF Deluxe Reverb

This is a Mojotone made clone of the AB763 circuit. It’s pretty much an exact copy in almost all ways. This came in making no sound whatsoever and had lots of issues. This was so problematic that it required a complete teardown and rebuild.

Amp was completely dis-assembled and rebuilt from the ground up. Multiple faults were noted including: shorted wiring, poor wiring placement, cold solder joints, and misplaced parts. All parts on the eyelet board were checked against the schematic and mistakes (especially around the Tremolo circuit) were fixed. All the electrolytic capacitors were replaced with higher quality MOD brand parts (increased temperature ratings) due to poor technique used in the placement and soldering of the originals. This included the filter, bypass, and bias circuits. The input circuits, screen resistors, and all socket/chassis mounted parts were replaced and re-wired for same reasoning.

All of the wiring was replaced with much higher quality Weico 600v/1000v Teflon Mil-Spec pre-tinned 22ga/18ga as the original non-insulated cloth wire was shorted/damaged and also is a fire hazard in this tech's opinion. The cloth wiring didn't allow the tight twisted pairs necessary to reduce noise and have an orderly layout. The wiring layout used replicated the original Fender Blackface AB763 wiring scheme exactly. The AC cord and all Transformer wiring was re-done for the same reasons as above.

The original tubes were damaged and prematurely worn so they were replaced with an entirely new set. V1/V2 = JJ 12AX7MG, V3/V6 = EHX 12AT7, V4 = JJ 5751 (Reverb Tank signal was a little too hot for a 12AX7), V5 = JJ 12AX7S, V7/V8 = JJ 6V6GT, V9 = JJ GZ34. The Fixed Bias on the 6V6GT's was set to 63% Class AB Plate Dissipation with a B+ of 456VDC. The pots were sprayed out due to scratchiness. Lastly the Reverb tank and all associated wiring/hardware was installed, the speaker wiring replaced (cloth wire here also a hazard), and the amp was re-assembled and tested. Amp now functions normally.