Rectifier problems: Are a 5AR4 and a GZ34 really the same thing??

[metropolis_4]

I’m having weird problems with the rectifier tube on my Divided by 13 JRT 9/15.

First I tried a New Sensor Mullard GZ34 and the amp immediately blew a fuse as soon as I flipped it off standby. I figured it must be a bad tube so I returned it.

Next I tried a JJ GZ34S. The amp turned on, no blown fuses I see the tube glowing, but when I flipped the amp on there is no sound coming out and the tube stays cold.

I guess there’s a chance I got two bad tubes in a row, but is there something else going on?

This is the tube that is in there now. Is there something special about this that I don’t know that would explain why it works? The tube chart for the amp just says 5ar4/gz34

 

[Blix]

I remember I had trouble finding good rectifier tubes for the Deluxe Reverb I had some years back, frustrating.
Ended up putting in one of these instead, and I even prefer the sound!

 

[metropolis_4]

I remember I had trouble finding good rectifier tubes for the Deluxe Reverb I had some years back, frustrating.
Ended up putting in one of these instead, and I even prefer the sound!

View attachment 52709

That’s a possibility. I think I remember hearing once that they can be hard on NOS tubes, is that true?

I’ve got some old NOS RCA JAN 6V6 and 5879 tubes in the amp

 

[QQQ]

As far as I know those two models are generally interchangeable. Not positive if there is an actual technical difference between the two.

 

[metropolis_4]

As far as I know those two models are generally interchangeable. Not positive if there is an actual technical difference between the two.

That’s what I always thought too. I guess it is possible I got two bad tubes in a row, but that seems like quite a coincidence. With the price of tubes these days I don’t want to try another one until I find out more

 

[PatF]

The solid state replacements probably don't have the same voltage drop through them as a tube rectifier. The GZ34/5AR4 is only about 10 volts drop but that might be enough to run NOS tubes harder than you want to. In the cathode biased Vox type amps the plate dissipation can already be really high.

Have you previously had a power tube failure? How do the solder joints look? Stray hairs on any wires? Measure for shorts and resistor values.

For a fuse blowing tube failure, I would recommend a socket replacement.

 

[metropolis_4]

The solid state replacements probably don't have the same voltage drop through them as a tube rectifier. The GZ34/5AR4 is only about 10 volts drop but that might be enough to run NOS tubes harder than you want to. In the cathode biased Vox type amps the plate dissipation can already be really high.

Have you previously had a power tube failure? How do the solder joints look? Stray hairs on any wires? Measure for shorts and resistor values.

For a fuse blowing tube failure, I would recommend a socket replacement.

What’s weird is that the rectifier that is in there works perfectly fine with no issues every time. I’ve only had problems when I’ve tried to replace it. No issues with power tube failure.

The rectifier doesn’t need to be replaced so I’ve got some time, but I do want to make sure I’ve got a working backup on hand so I need to get this figured out

 

[AutomationBias]

How old are your filter caps?

 

[metropolis_4]

How old are your filter caps?

4 years

 

[metropolis_4]

I figured out the problem with the Mullard. Turns out I had it oriented wrong!

The keyway on that tube is so small that it’s possible to misalign the guide key when inserting it and it still fits in the socket. I’ve never seen that happen before. I didn’t even know it was possible.

 

[QQQ]

Thanks for sharing the resolution.