One of the dumbest things Fender did when they designed the Blues Junior and Pro Junior was to substitute a dinky little plastic lens for the traditional faceted jewel and #47 bulb. People have been asking me for years to install the jewel light assembly, and for years I’ve tried to talk them out of it, for several reasons.
First, you have to drill a humongous hole in the front panel. The extension that holds bulb socket barely fits over the circuit board. Next, it’s nearly impossible to tighten the nut that holds the threaded assembly unless you more or less gut the chassis so you can get in there.
The existing wiring won’t run the #47 bulb. It is designed to run an LED at reduced current and voltage. This is actually a good idea: less load on the power transformer, less heat. So you have to modify the bracket by cutting away the socket, shortening the arm, bending and drilling it, and installing support for a white LED. This assumes that you want a jewel other than red. If you want red, you can use the existing red LED, but you still have to modify the plastic “flower” that clips to the stock red lens.
I finally came up with a solution that is aesthetically and mechanically acceptable to me. I took my cue from the Series III Blues Junior, which has a non-removable red jewel and a red LED. Instead of the bulky ring around the non-removable lens with a thin nut on the back, I figured, why not thread the chassis and attach the lens directly? The resulting look is clean, minimalist, and doesn’t require a huge hole:
But that doesn’t mean it’s easy.
All of the lenses and holders I’d gotten from online vendors were metric, 14mm, super-fine thread. My first goal was to find a nut to fit them. Impossible.
I finally found a vendor, Antique Electronics, that sells jewels with an inch thread, 9/16″-24. I still couldn’t find a nut in that size, but I could at least buy an (expensive) tap in that size. To install it, though, is still tricky. I drilled the chassis with a 33/64″ bit, the right size to get proper thread engagement, and drilled the face plate to 9/16″, so the threads would not bind on the face plate, but the lens would seat against it. Then I tapped the chassis with with a 9/16″-24 tap. Don’t attempt any of this unless you have a drill press and a way to firmly clamp the chassis vertically. You also need to hold the tap solidly square to the faceplate as you cut the threads or you stand a good chance of ruining the cut with an off-angle thread or a cross-threaded mess. Again, a drill press is ideal for this.
I removed the red LED from the “flower” and soldered a white LED to the leads. I trimmed the “petals” so the plastic would fit inside the lens. I secured it with a dab of hot melt glue.
Since this mod requires equipment that most folks don’t have, I’m offering it as a service for amps that come in for the Billm mods. There’s a waiting list for that, of course.