JJ GZ34 failures

[Randall]

For the second time in about a year I have had a new out of the box JJ GZ34 fail, and with the same symptoms. I just re-habbed a 66 Fender Pro Reverb that was inoperable and included a scary looking SS rectifier with the tube and socket removed. After rebuilding the tube rectifier and moving on to other issues I experienced the GZ34 to throw a big spark on power up every once in a while and blow the 2 amp breaker I had clipped in for testing. (cheaper than fuses). Since the rectifier tube doesn't produce any DC until it has the opportunity to heat up, I attribute this to the tube sparking internally. After replacing it with an old RCA , this problem has not since occurred.

Has anyone else experienced this type of hard failure with JJ GZ34's?

[Jazz P Bass]

Yup.

They are junk.

Sovtek had some problems years ago but they got them sorted out.

Or try the Shuguang.

I buy old RCA's occasionally on EBay.

[pdf64]

Do you mean that it arcs / shorts when mains is applied to the PT, or when standby is flipped to operate mode?

[Zouto]

YES, they are junk, waste of money, time & nerves. Shuguangs and TADs also tend to blow occasionally, I found newer Sovteks to be reliable & stable.
Zouto

[Leo_Gnardo]

Has anyone else experienced this type of hard failure with JJ GZ34's?

Yes, they had a bad period about 5 - 10 years ago, and I gave up on JJ GZ34 then. Possibly they've improved since, in seems all of the JJ line has, but without doubt some of the JJ GZ34 baddies are still in circulation. I'd hate to think they've upped the quality average on the rest of the line but still sending out dodgy GZ34s but who knows. I don't feel like shelling out the money to experiment.

Our resident expert Stan claimed Ruby's GZ34/5AR4 to be the best in production. Chinese made but not by Shuguang. As a repair shop you can start an account & order direct, or possibly buy a couple at a time from a good vendor like Doug's Tubes or Valve Queen. I've been using these regularly in recent years and rarely have a problem. Note Ruby is a job shop supplier, please don't pester them with dinky size orders. $200 and up per order, you're good to go.

[Mick Bailey]

I've replaced quite a few shorted JJ GZ34 in the past, but no recent failures in the past couple of years. Having said that, I got a Matchless Independence in for a regular service and after only 12 months the JJ rectifier was discoloured internally with a brown stain inside the envelope, like you get with old Mullard EL84s. So that got replaced as a precaution. Doug's currently lists JJ GZ34 under the Ruby brand.

[mozz]

Is there a date code on the tube that is sparking?

[Randall]

I find no date code.

[andywragg]

Had the same happen to me with my JTM 45 home build. Talk about lightning in a bottle!! Replaced with a TAD been fine ever since.

[diydidi]

I have been using the JJ's with great success. I add two diodes as backup diodes to protect the PT should the rect be fail short.