JJ brand 5AR4 issues

[Mars Amp Repair]

Hello folks,
Has anyone had the repeated experience with the JJ brand 5AR4 rect tubes?
I have had numerous issues where these tubes will arc/short on with the initial inrush current even where the amp is designed to use the 5AR4.
I had an amp that drew enough inrush that a few of the JJ 5AR4's would initially arc internally, and then settle down & work until the next inrush.
So, I won't use them anymore. I'm not sure who is the ultimate mfg of these.
I have found the Sovtek or Tungsol made rects do not have this issue. I compare the internals of the Sovtek & the Tungsol reissue rects, and they seem very similar, so I'm guessing the Tungsol is Sovtek made.
So, I use the Sovteks, as they're a tad cheaper.
What you think?
Thanx, Glen

[The Dude]

I can't remember which thread, but we discussed this here a bit ago. Others, including myself, have seen that problem crop up recently. I never had that problem in the past with JJ's, but it seems to be a new "thing". I hope they get it sorted.

[Mick Bailey]

I've had a few failures with these tubes, but exclusively where amps feature standby switching. The fix in every case has been to wire a resistor across the standby switch. My default value is 47k, 5W. By the time the tube is conducting, the first smoothing capacitor after the rectifier has charged to around 80v which reduces the inrush current. I place a prominent label inside the amp to alert the next person to what's been done. With some amps standby doesn't completely silence the amp but I've found that amps that came back repeatedly with shorted rectifiers never come back again once 'fixed'.

A well-documented amp that had problems is the earlier re-issue AC30s, but others have the same problems with certain tube brands.

[Tom Phillips]

... Others, including myself, have seen that problem crop up recently. I never had that problem in the past with JJ's, but it seems to be a new "thing". I hope they get it sorted.

My experience is the same as Dude's. I've been using up a large buy of JJ 5AR4's that I acquired between 6 and 10 years ago. I'm down to the last one from that batch and have had no issues with any of them.

[Mars Amp Repair]

I've had a few failures with these tubes, but exclusively where amps feature standby switching. The fix in every case has been to wire a resistor across the standby switch. My default value is 47k, 5W. By the time the tube is conducting, the first smoothing capacitor after the rectifier has charged to around 80v which reduces the inrush current. I place a prominent label inside the amp to alert the next person to what's been done. With some amps standby doesn't completely silence the amp but I've found that amps that came back repeatedly with shorted rectifiers never come back again once 'fixed'.

A well-documented amp that had problems is the earlier re-issue AC30s, but others have the same problems with certain tube brands.

Ah! I remember that now. I can recall doing that on a Sunn Concert or Colosseum that just kept eating up the 5AR4 JJ's until I realized that those tubes for some reason don't hold up like the Sovtek's.
Thanx for that reminder. glen

[Leo_Gnardo]

they seem very similar, so I'm guessing the Tungsol is Sovtek made.

True, those and other Russian brands like ElectroHarmonix EH, Mullard, Gold Lion and I'm sure a few others are all made in Saratov, all part of the New Sensor empire.

About 2006 I started using JJ 5AR4 and installed many with excellent results. Somewhere around 2011 I got a batch and most went up in sparks. Salesman informed me they just returned a batch of 200 defects back to Slovakia with some suggestions where to stuff them. QC must have taken a holiday at JJ. Took a while to regain my trust. Recent years I haven't had many failures as I recall, perhaps none. With your report, maybe there's another QC failure at JJ. Thanks for the warning!

[SoulFetish]

If my memory is correct we got a bad batch around a year and a half ago(I think). We offer a replacement guarantee on the service life of the tubes we install of around 90 days, so we act quickly when we see a trend of failures. We've had good success with the Sovtek brand 5AR4, and I personally like the small envelope they are constructed in.