Pictures of Updates

Tonight was exciting because I got to verify the potentiometer and play through the two new modes of my amp: Using the JP1 circuit (off) and cutting the JP1 circuit out (on). I noticed that the sound was noticeably louder, but also sounder cleaner when the switch was on. I also got to verify that my component swap went successfully. I accidentally knocked the C1 capacitor off with the drill, woops, and so I replaced it with the only Silver mica capacitor I could find. The stock C1 was .022uF (22,000 pF), and I replaced it with a 120 pF capacitor, which is much smaller. The amp sounds nice now, and I plan to get the tone modifying components in it soon.

New potentiometer. 

I had to unscrew the main board from the chassis...

To solder in the switch to cut out the JP1 circuit. 

Got the 2-way switch soldered in.

This was a tough solder job, as one solder spot was right next to that white connector. 

I drilled holes for all three switches, since I already had the drill out. 

Far right switch hooked up, other two are blank for now.

Attached the main board back to the chassis. 

Front of the amp currently. I'll probably remove the On/Off logos. 

Setup for E-Day in the SPaRC Lab!

Added On/Off Switch for the JP1 Jumper

So I ordered more on/off switches, since the ones I ordered from Hong Kong will arrive sometime in 2014... these new ones I ordered from America. The JP1 jumper on the Valve Jr. is pretty much a wire that brings the output circuit into contact with a capacitor, which decreases the quality of the output signal. I wanted to wire this out of the circuit, but still have an option to switch back to the JP1 circuit if need be. I wired the input and output of the on/off switch into the two JP1 holes after I removed the physical wire that was present before.

There was, however, one casualty. While drilling a hole for the one/off switch, I knocked the C1 capacitor off of the board. Like completely off, ruined capacitor. I haven't tested the circuit yet, but I assume this isn't good... I'll be looking up the value of C1 and searching for a high quality replacement soon. Anyways, using the drill was awesome. I used the largest bit available in the lab, which is 1/2". I originally had it drilling clockwise, and it wasn't getting through very well. I eventually tried reversing the direction of the drill, and then it went through the chassis with ease.

E-Day is tomorrow, so I will be displaying the amp and the current mods in the SPaRC lab.

Verified New Potentiometer

I did what everyone in electronics is warned against, and testing my guitar amp with exposed components. I lived, so it's all good. I verified that the new potentiometer, which is a variable resistor, works. Not well. As I said last week, my soldering iron sucks, so I have to take this back to the lab. I was going to wait until I got my 2 way switches in, but I just noticed I ordered them from Honk Kong. Which means 6-8 week shipping.

Anyways, I tested the new pot hanging outside of the chassis. It is scratchy, which means I have a bad connection. So I'll re-solder that soon, as well as drill a hole for it to fit inside the amp.

Pot Change on the Volume Control

I got a few parts in this week, including the matched set of JJ Tubes (EL84 and 12-AX7), the new potentiometer (for the volume control) and a 120pF Silver Mica Capacitor. I'm still waiting on a few switches to modify the JP1 capacitor out of the output circuit, and to add a "Bright" and a "Fat" sound modification.

Matched set of JJ Vacuum Tubes

Old pot.

Nice shiny new pot. 

Unhook this cable first.

Old pot on board on the left.

Both are 1Mohm potentiometers.

With the new OT, amp can sit upside down nicely. 

Had to add wires for the new pot. 

I installed the new potentiometer, but it was a huge hassle. The new pot's pins didn't fit inside the pot board, so I used some short wires to hook them together. I set up a lab at my house to work on this project, and just found out my soldering iron doesn't get hot enough to melt the solder on these components. I ended up borrowing my neighbor's gun for the time being, but I'll have to move back to the lab. The new pot is too thick to fit through the previous hole in the metal chassis, so I have to drill a larger one. I'll save this until I get the switches in, because I'll have to drill three holes for them anyways. 

The installation of the tubes I will save for later, so that I don't cause unneeded strain on the new tubes while I'm testing. 

Amp Test After OT Install

I took the amp and cabinet home today, and it worked! This is really exciting for me. It seems like most times I solder something, it breaks and never works again. YouTube video of the demo:

I was searching for two Dual Pole Dual Throw switches (DPDT) in the SPaRC lab today, and found these two candidates. After some research, they failed the test.One is a Single Pole Single Throw (SPST), and the other is a Single Pole Triple Throw (SP3T), so neither will work for my purposes. I also didn't like the ease of movement of these switches--they would be difficult to flip quickly and accurately. I am installing a "Fat" switch and a "Bright" switch to modify the tone at the flip of a switch, and have ordered my desired switches on Amazon.