I decided to do the basic and output transformer mods from the billm website in the hope that I can get a tighter low end and more headroom before it started breaking up.
- Tone Stack
- Power Supply Stiffener
- Bias Trimmer
- TO20 Compact Output Transformer
- Swamp Thang Speaker
I mentioned in the last blog that my Blues Jr is a legacy model. That means they aged it to look like it has been kicking around for a long time. They put a rip in the speaker cloth and even put a beer bottle stain on the top. They also aged the screws. The whole screw even the threads. They must have dipped the screw in acid then put them in wet or at least still oxidizing. This makes it difficult to remove the screw. I was able to remove all but two of the screws. I tried WD40 before I started cranking away. I eventually stripped the head as the next photo shows in glorious detail. Ok, so now what? There is only one way out of this mess that I know. DRILL IT! I've had to drill screws out like this before so I knew what I was getting into. I needed to find a drill bit that was wide enough to take the head off the shaft without damaging the cabinet. The bit also had to be tough enough to get through what ever material the screw was made out of.
Most of these types of screws are made out of zinc plated steel. I know it can't be stainless steel because it is rusted. Right? The folks at Fender probably roughed the screw up with a wire brush to remove the zinc, then dipped the screw in acid to give it that "Legacy" look. I picked a 7/16" titanium drill bit. The 7/16" is just a bit wider than the screw head and titanium is harder than most steel.
I admit the choice of titanium might be overkill but I only get one change to get this right. And, I don't want to do damage to the cabinet or the tweed. The titanium will allow me to apply the least amount of down pressure with the most cutting force.
The drilling went well. You can see the large piece that came off of the screw head and minimal damage to the cabinet. The new screw will cover what damage has occurred. Notice all the small pieces of metal. Be sure to vacuum all these up. A small piece inside the chassis can cause major damage.
The screws are out and we can remove the cover to get at the heart of the project!
The next photo shows the removal of the remaining screw shaft left behind. I hit it with some WD40 (the red tube) and grabbed the shaft with a pair of channel locks. Wiggle the shaft right to left to get it to loosen up. Then start twisting it to remove it all the way.
Finally, we are inside the amplifier and everything is cleaned up. Make sure you clean up the WD40. It can attract and hold metal chips and dirt. Not good inside the chassis with high voltages around.
Next time, we look at the "Basic Mod Kit" from billm audio and plan our attack!