Remember back in the beginning of January when I traced the failure of the Lacewood amplifier to a failed JJ power tube? Well, here we go again.
Another JJ power tube went south on me today. This one was a 6L6 in the Spalted Alder Amplifier. Luckily this time the failed tube just died and didn’t try and fry my amp at the same time. But it is yet another JJ power tube to suffer premature failure in the last six months or so. This one just quietly had the heater open up.
Shorts, opens, buzzing, crackling, flashover,… Just what in the world is going on with JJ power tubes? I checked, and the failed JJs I’ve received in the last year have come from three different suppliers. This isn’t a reseller issue, or a bad lot, this is something specifically wrong in the JJ factory making 6V6S and 6L6S tubes.
I’m done buying JJ power tubes for a while. It’s not that I’m really angry or anything. It’s just frustrating when a product which has worked well for you for years suddenly goes south in such a spectacular fashion.
As always, questions and comments are welcome.
Follow Up - 14 February 2025
I heard back from the folks at JJ in the Slovak Republic. Evidently there is not any systemic production or quality problem of which they are aware. They also responded with:
But, in any case, we are surprised by your email, because recently there are minimal complaints about quality of JJ vacuum tubes …
So it looks like it’s either something I am doing or I got a batch of counterfeit tubes from one of my suppliers. Unfortunately I no longer have most of the failed tubes in my possession. I will investigate further as much as I can. However at this point I am refraining from making any specific recommendations except for people to keep track of where they purchased individual tubes so that systemic problems can be tracked.
Right now, the only JJ power tubes I have in regular use (daily) is a couple of 6L6GCs in the Spalted Alder amp. I’ll keep an eye on them. And I remind everyone that I have had no issues with any other JJ tubes. The signal tubes and rectifiers are great performers with seemingly long life.
Regards.
Follow Up - 12 March 2025
So I had another JJ 6L6GC fail today. They are failing in a way that results in excessive current draw. The only thing I can think now it that this whole batch of power tubes came from a supplier that “matches” tube pairs. I am wondering if maybe they stressed the tubes in some way during this procedure. I can’t be sure so I won’t name the supplier. But it pays to be careful. And remember that none of my designs require matched tubes.
Regards.