I see quite a few Fender Blues Juniors in the workshop for repair; not that they are unusually unreliable, it’s just there are a lot of them out there!
However you do see many of the same faults occurring, so here’s some photos highlighting these from a recent repair.
Firstly, like many amps that use EL84s, the power valves are run very hot. This isn’t helped by Fender wiring their European export amps for 230 VACmains , rather than 240 VAC. This means that all the Fender amps sent to UK run on higher voltages than they should.
I always rewire any Fender amps I have in the workshop to UK voltage.
As you can see from the photo below (not my best effort with the camera) the filter caps in this amp had started to leak. This seems to be an unusually common problem on Fender amps from the mid nineties. Whether Fender got a bad batch of caps, I don’t know.
Regardless, Illinois Caps (IC) don’t have the best reputation, so if I need to change any of the filter caps I change all of them. I like to use German-made F&T caps for this.
The pots get easily damaged on the Blues Junior. Often the tabs work loose on the back of the pots, so I always bend these back in with some pliers.
Finally the heat from the power valves often causes damage to the solder joints on the sockets for these valves. There is also a dry joint on the ribbon cable from the main PCB. I resoldered all of these.
A pair of new valves and adjusting the lead dress to eliminate oscillation, another common problem with the Blues Junior and the amp was repaired.