Fender Blues Jr Bias Kit

Fender Blues Junior amps have one major design weakness. They use non adjustable grid bias in the power stage, and it’s usually set far too high. We have  seen as high as 130% idle bias on units straight out of the factory. It’s no wonder so many of them can ruin the pcb.  

The issue is made worse because Fender set the mains voltage on these ampds to 230 volts and in relaity the mains voltage in the UK is usually around 240 volts or more ! This will strain the EL84’s even more. Your local tech can set these amps to run on 240 volts. 

Some examples run the EL84 output valves at 130% of full power. The valve pcb is slowly cooked and the EL84’s life is greatly shortened. This kit ensures maximum EL84 output valve life AND ensures that the valve pcb does not get cooked.  There is a solution with the Fender Blues Jr Bias Kit.

This is an easy to fit kit which adds fully adjustable bias to your Fender Blues Jr. You will need soldering experience to fit this board and to be able to set the bias,.

This Blues Junior Bias mod kit is designed so that in the unlikely event of the pot wiper going open circuit, the power valves grids swing negative, saving the valves. Much of the advice on the internet about doing this mod misses this critical point  – other  mods will leave the grid floating up towards GND in the event of pot oxidation, which will destroy the power valves.

We have partnered with Keld Ampworks and we will be offering this nice little kit in April. 

Check out this YouTube Video  and see how to fit this board.