Mojotone 6G15 Reverb Unit

Mojotone 6G15 cabinet

A while back I was looking for a project that wasn’t going to take up a lot of room and decided on the Mojotone 6G15 Reverb kit. While mostly a straight forward kit I did run into a couple of “gotcha’s” along the way. The kit is almost an exact replica of the original Fender product. I elected to use original value components so I went with 40mF filter caps and a NOS 6K6GT in place of the 20mF and 6V6GT supplied. To be honest I played with both configurations and I can’t tell the difference but being a grumpy old coot I stayed with the original schematic with the exception on the grounded power cord.  More on that in a bit. 

Completed, but prior to changing over to a two wire polarized power cord

Assembly was straight forward except as drilled the power transformer frame was nearly touching the hot terminal of the power switch. Looking at pictures of the original units I saw the transformer was really stuffed in the far corner so I drilled new mounting holes for it. Unlike most installations the power transformer is mounted on the inside of the chassis so there is no large cut out to deal with. I also used an original style low profile Carling SPST instead of the larger DPDT supplied with the kit. That left plenty of room. Otherwise it was Mojotones usual easy assembly. I wish they had supplied a blackface front panel with it, but the tweed style chrome looks fine and I suspect they don’t sell enough of these to justify the expense. 

The chrome panel works, but I would have preferred a black face panel

The only functional problem is that with a 3 wire power cord you have a serious ground loop. The original Fender used a 2 wire power cord and unlike every other Fender amp till the ‘70’s had no “death cap” circuit avoiding ground loop issues. If you put a 3 wire plug on them you get the same problem. The Fender reissues are circuit board built and are designed with separate signal and chassis grounds. After playing with the options I elected to go with a polarized two wire power cord since a chassis ground is established through the instrument cable to the amp, but there may be code issues preventing Mojotone from doing that. Other options are using an isolated box on the cable between the reverb and the amp, using a ground lift plug, or using an isolation transformer on the power cord. All that being said, the 6G15 Reverb sounds awesome and I have no regrets.