Well apparently I had looked at the pinout diagram of the 6X4 wrong. I thought this mod would only require two wire jumpers, but one of the two pins that needs to be swapped has to actually be moved to a new spot in the socket itself. Thankfully this extra step is very easy due to the design of the socket.
6X4 Rectifier Modification
Rectifier Pinouts
The difference between the 6Z4 and the 6X4 is that one of anodes and the cathode are connected to different pins. The 6X4 draws 600mA for it's heater and I assume the 6Z4 draws 300mA, but I have no idea since I can't find a data sheet for it.
Stock Layout
Here is the stock layout using the 6Z4 for reference.
Step 1
The first thing you'll have to do is de-solder pin 5 from the PCB. Try to clean the majority of the solder off it too.
Step 2
Bend the pin straight up and remove if through the other side of the socket.
Step 3
Next de-solder pin 7 from the PCB and bend it a bit to the left like shown in the pic.
Step 4
This step is just a safety precaution against possible shorts. Scrape away the corner of the trace near pin 7 as shown in the pic using a heavy Xacto knife or a small file.
Step 5
Craft a little wire jumper similar to the one in the pic. This will be used in step 6.
Step 6
The jumper will be connecting pin 7 to the trace that pin 5 did originally.
Step 7
This is where we reinsert the pin that we took out in step 2. Put it in the hole for pin 6 and bend the tab towards the center of the socket as shown in the pic. To avoid excess play make sure it is fully seated before you bend the tab.
Step 8
Craft a little wire jumper similar to the one in the pic. This will be used in step 9.
Step 9
For the final step, run the little jumper from pin six over to the trace that pin 7 originally connected to as shown.
Comments
This mod is fairly easy to do if you've worked with jumpers before. It's a little tedious to get them to fit right, but just take your time crafting them. If you plan on doing this mod keep in mind that you'll
have to disconnect the heater in the 6N1 up front or you will burn up the transformer. The heater winding feeding the 6Z4 and the 6N1 is only rated for 600mA and since the 6X4 draws 600mA by itself, there's no way you can have the 6N1 connected too. You could probably leave the orange LEDs in the front window connected since they draw so little power.
Please be careful about keeping your work clean since these pins carry HV. Needless to say,
I assume no responsibility or liability for damage to you, your amp, or your other equipment by doing this modification. If you are not confident in your soldering ability PLEASE don't attempt this mod.
Results
So far everything is running smoothly. I've been listening to the amp for about two hours and the transformer isn't overly warm, but I'll keep a close eye on its temp.
At this early stage, I would say that the amp does indeed sound better with the 6X4. The sound seems a bit more crisp and overall the sound seems a bit more detailed, but I want to give it some more time before I judge it.
Stock 6Z4 vs. Tung-Sol JTL-6X4
PS with 6X4
