JJ GZ34 Issues ??

[Blind Lemon]

Just wanted to see is anyone else has had issues with the JJ GZ34, I have bought them a at a time dozens and it seems like one or 2 out of the batch will have a short. Bad thing is I have to eat them as my supplier won't make good on them after a short return time. I stock quite a few tubes for repair work and new builds, I really don't want to set up a test fixture just to burn in rectifiers.

I've switched to the TADs and they are quite a bit more expensive but have not had any issues so far. What are you using?

Not wanting to bury JJ or my supplier but was wondering if anyone else is having the same troubles?

[TUBEDUDE]

Chinese, they apparently redesigned them so they're no longer pyrotechnics. Buy from a dealer that burns them in. Upscale Audio does well.

[didit]

Hello -

My consumption is personal use only, and occasionally support for friends. Had a brief run of bad luck or simply bad JJ GZ34s--three out of three over a short while. After a tear down examination came to believe it really was design weakness--that was a while back so please don't expect any recounting of the details. Since then had good results from Russian (Tung Sol 5AR4) and even better results with TubeStore "Preferred Series" 5AR4 (believe Chinese-built to their specs and then tested).

For what it's worth ----

Best .. Ian

[Stevem]

You had best forget about China made tubes very soon since there one factory burnt down last year!

[didit]

You had best forget about China made tubes very soon since there one factory burnt down last year!

No worries here, given the dozen or so per decade I consume. TheTubeStore still lists their variant available. Had read about that fire, and understood it was in a building adjacent to the manufacturing equipment. And that a new factory location was already in the works. The reports anticipated production to restart sometime this coming year but COVID so who knows.

And a New Sensor 5AR4 (labeled Tung Sol) seems to be robust (so far after about a year in-service).

Best .. Ian

[wpaulvogel]

I have a collection of Mullard Blackburn F32’s. I generally don’t use rectifier tubes but I have these just in case.

[Leo_Gnardo]

I've been using Ruby 5AR4/GZ34 for many years now. I ran into the JJ problem years ago - about 10 - and never ordered them again. Same frustration with returning bad ones. Bad enough if they go bad in an amp under test, and worse yet if they go bad in a customer's amp on stage or in studio. Sometimes they make it just past the 60 or 90 day warranty. And the supplier wants me to send the bad ones back, so the only winner is UPS, Fedex or US Post Office. Phooey.

If I'm not mistaken Ruby has their own China facility for these rectifiers, they're not made by Shuguang. They were designed to be as near a perfect copy of the famous Bugle Boy rectifier. I'm not saying they're absolutely perfect, on occasion I've had one go bad, but it's not a regular thing like with JJ.

[M Fowler]

I changed to Sovtek per Don at Dr Z's advice.

[Travis_HY]

I had similar issues maybe 6 or 7 years ago. I had much better luck with the Sovteks and in one instance I switched over to a Weber Copper Cap rectifier and it put out almost exactly the same (5vdc higher) DC. An added plus is it doesn't require the additional 5vac heaters so the PT could run a little cooler.

[pdf64]

...I switched over to a Weber Copper Cap rectifier and it put out almost exactly the same (5vdc higher) DC.

I suspect that measurement will have been the HT voltage at idle? If the HT at full load had been checked, the voltage with the copper cap would almost certainly have been somewhat lower than with a functional GZ34. With a typical 40W amp, that hobbles the amp's power output, especially so when overdriven, producing a power compression effect, similar to swapping to a 5R4.
The reason is that a valve rectifier doesn't have a linear 'voltage drop to current draw' relationship, so one 'sag' resistor value with silicon diodes can't provide an equivalent output over a range of loading. With a GZ34, my finding is that about 80ohms provide a similar idle HT, whereas at full loading, it need to be reduced to about 20ohms. I seem to remember that my WZ34 copper cap uses a series pair of 39ohm resistor (and a pair of silicon diodes and NTC current surge suppressor.

An added plus is it doesn't require the additional 5vac heaters so the PT could run a little cooler...

That's certainly an advantage if the PT doesn't have a 5V winding; but in that scenario a suitable sag resistor seems cheaper and safer.
If there is a 5V winding, then the <10VA load presented by a GZ34 heater seems minimal, unlikely to make a ha'penny worth of difference to the operating temperature PT of a typical >15W valve amp.