GZ34 to a 5U4

[greenfields]

I find my mid 70's Fender Princeton amp with a GZ34 rectifier is a little stiff.

I want to try a 5U4 rectifier tube. Will I experience any problems by doing so or will the amp be fine?


Thanks

[tmarra]

If I remember right the 5U4 draws double the heater current of a 5AR4(GZ34). This will put some strain on your Power Transfomer.

There is another NOS rectifier with the same "sag" of a 5U4 but less heater current but I can't remember the number off hand. I know I have a couple I bought from a NOS tube vendor at my shop.

-Tony

[DeeringAmps]

Put a 5Y3 in it.
Tony is right, the 5U draws 3 amps opposed to 2 amps.
Generally the Fender iron is pretty stout; your amp, your choice.
I prefer the Sovtec 5Y3 because it is a "slow" turn on like the GZ-34.
Some feel it is just a 5AR4 in a different package; not true in my experience.
I run the Sovtec 5Y3 in all my low power amps.
Just my nickel .98

Tom

[Ron Vogel]

I ran a 5u4g in my Princeton when I first got it...too much sag, and output voltage to the tube was all over the map depending on which brand I put in. I found the GZ34 to be perfect all around.

You may need to get a proper bias/set-up for modern voltages with that GZ34, and that's why it's so stiff. I had to increase the value of almost all the dropping resistors to the rail on my Champ for the very same reason.

Putting in a 5Y3 would probably work, but you may "brown" out the circuit to the point where you have no headroom past 3-4 on the volume knob.

If you are comfortable around tube amps, it would be wise to see what kind of voltage you are seeing at the 6V6's and preamp tubes before you go swapping.