1968 Pro Reverb rectifier flash

[tdlunsfo]

I took Mike Baileys advice and the 47k trick seems to be working but will definitely check out the Sovtek GZ34's for next time.

[The Dude]

The JJ GZ34 problem seems to have cropped up only recently. At least that's my experience. I never used to have problems with them, but recently have seen lots of them defective. I hope they figure it out. Just last month I had 2 new fender amps with JJ GZ34 come into the shop. Both had arcing rectifier tubes.

[tdlunsfo]

I haven't had issues with them either until now, but granted I don't replace a ton of rectifier tubes.

[Randall]

FWIW, I have had a couple of bad JJ GZ34s right out of the box in recent years. I no longer use them. I use Ruby now for rectifiers.

[Chuck H]

The JJ GZ34 problem seems to have cropped up only recently. At least that's my experience. I never used to have problems with them, but recently have seen lots of them defective. I hope they figure it out. Just last month I had 2 new fender amps with JJ GZ34 come into the shop. Both had arcing rectifier tubes.

You know... There was a time when it was one of the JJ and one of the Sovtek model 12ax7 tubes that were dropping like flies when used in the Marshall cathode follower circuit. Then there was a run of JJ 12ax7's that were obscenely noisy when put in the V1 spot for higher gain units like guitar amps. Then there was a Sovtek 5Y3 for a while that was actually a re labeled 5V4 judging by the voltage drop (or lack of). A few years ago I went through a couple of pairs of JJ EL34's trying to find a tube that would hold up to 490Vp and 470Vg2 in a build that were incinerating the screens when clipping. Now we have JJ GZ34's that arch. I think someone needs to tell these Rusky's who's buying their tubes!?!

EDIT: JJ's were Czech for a time and then I think they went to Russia? I don't even know where they're made now so forgive me please if I'm off.

[Tom Phillips]

You know... There was a time when...

I also seem to remember a time when someone was selling 5Y3s marked as 5AR4s.

[Chuck H]

I also seem to remember a time when someone was selling 5Y3s marked as 5AR4s.

I don't remember that one. But I'm not part of the real front line in repairs. Not surprising. I do know that in the above mentioned amp needing a pair of robust EL34's I ended up with Ruby selected Shuguang tubes. I bought three pair and chose the least microphonic of them This was a combo so it not only needed tubes that could take the heat, but also be somewhat mechanically sound. The Shuguangs were ALL microphonic either moderately or grossly. My understanding is that the current EH EL34's are good tonally. electronically and mechanically. So at least there's an option now. Not to derail the thread too much but in light of all this I actually wish the Shuguang folks could get their operation back up sooner. China has been through the same shizzle as the rest of us with more stringent dictums on protocol. I think Shuguang hopes to resume manufacture about a year from now? I haven't checked lately but they were in the process of moving their whole factory when the $#!t hit the fan.

[pdf64]

JJ are in Slovakia, the south eastern part of the old Czechoslovakia, which split (amicably) into the Czech Republic and Slovakia 30 years ago. Both are EU and NATO member states.

[pdf64]

I also seem to remember a time when someone was selling 5Y3s marked as 5AR4s.

I think it may have been the same Soviet rectifier that Chuck referred to as a 5V4?
Dunno what the true type designation was.
I got one about 25 years ago, used it occasionally to drop the HT and power output of my old AC30 a little.
Edit - here it is, between an RCA 5Y3 and Mullard GZ34