We repair a lot of Fender Blues Juniors.
One common problem is the pin 7 of the left hand EL84 valve shorting to the cathode via a PCB trace which has erroneously been run too close to pin 7.
We have thus designed a replacement PCB that avoids these faults. This is a high quality PCB: 1.6 mm FR4, 2 oz copper, plated through holes.
I've written a more detailed blog post
about this with some pictures.
If any FB members want PCBs get in touch and I'll do you a better price than via eBay.