Anyone Else Have Trouble With JJ Tubes?

[goldear]

How do their KT77's hold up?

I've had one fail on me. But that amp had a loose ground on the cathode. So I'm not sure that it is fair to blame that failure on the tube.

Other than that one bad experience, I think that the JJ KT77s tubes sound amazing. No other current production EL34 type tube I have tried touches these tubes sonically IMO.

But, FWIW: I will only buy JJs which have been burned-in for at least 24 hours by the dealer first. I figure that this should increase the chances of the dealer catching a bad tube before it gets sent to me.

 

[Funky54]

Buy the amp you want, even if it has new JJ tubes in it. Pull them and sell them, and put what you want in it.

Regards
Mister Pig

Wait..what? Stop. That is just too much logic and sensibility. This is Audiokarma, we need to debate if we should cryogenically freeze them or draw a green marker line around the base for at least 12 more pages before a post like this appears.

 

[getter365]

My experience with JJ tubes is limited but here goes. I purchased a matched quad of 7591S tubes a few years ago. I have usd this quad in various HiFi (not guitar) amps and receivers. I do recall one of the tubes lit up (or flashed) near the top momentarily when new. But I tested them on my tester and they all still were good. Since that incident, I have used this quad for years with no issues. I like the way they sound too. But I do think the EH 7591A tubes are more solidly constructed from a physical point of view. I havent use my quad of new Tung Sol 7591A tubes so I cannot comment on them.

I also recently bought a new JJ GZ34(5AR4) and am using it with no issues. It tested strong and balanced. I may replace it though because its diameter is larger than the orignal one and that places it closer to a transformer.

Also, maybe the guitar amps u experienced have had their share of shock and vibration. Maybe the JJ ones are not as physically sound as others, but this statement is just conjecture.

 

[GordonW]

This sort of thing makes me want to just find a couple of killer solid state amps and live with them.

Find an amp that uses 6L6s.

Actually, that's not really a joke. Given HOW MANY 6L6-based guitar amps there are, and probably always will be- and HOW MANY DIFFERENT manufacturers make them- it's unlikely that we will ever have a time, where there isn't at least one or two companies making good, high-quality 6L6s.

Regards,
Gordon.

 

[GordonW]

I must also respectfully disagree here, regarding multi-section caps. There is no inherent reason why they must be inferior. But back to topic, as said in a previous post: I have used dozens of JJ 50+50µF-500V and 100+100µF-500V caps over more than 20 years and never had a single problem (also always measured each one for capacitance, leakage etc.). Construction is necessarily more expensive; depends on what mounting flavour you want.

(Not that I have not also successfully used other makes like Hitano, Panasonic, Nichicon and Philips. But the question was regarding JJ - and those JJs come in 500V; most others are rated 450V.)

This is very similar to my experiences, too. Though, I've only really been doing tube restoration for about 15 years...

I also have used all the brands mentioned, and the JJs are no more or less problematic than the others, on average.

There's a real dearth of caps rated at higher than 450v- the JJs, some Illinois (500v), and even a few 600v caps here and there. When you're working with high-power KT88 or EL34 amps, or some of the 6L6 amps with "the wick really turned up", you oftentimes wind up dealing with B+ voltages (at least at startup) of 475v or more. The JJs seem to work fine, here, IME.

Regards,
Gordon.

 

[Pio1980]

Find an amp that uses 6L6s.

Actually, that's not really a joke. Given HOW MANY 6L6-based guitar amps there are, and probably always will be- and HOW MANY DIFFERENT manufacturers make them- it's unlikely that we will ever have a time, where there isn't at least one or two companies making good, high-quality 6L6s.

Regards,
Gordon.

I have a project amp that I specified for "cockroach" tubes, 6L6 and 12AX7, using Fisher/ Todd OPTs. Also a Silvertone console amp with 6BQ5/ EL84 and 12AX7. I've done pretty much what you suggest for the reasons you mention, both nice amps.
Also have an upgraded Iverson Eagle 2, OCM Soloist 200 FET by Dave Belles, an Adcom GFA-545-II, and somehow, 3 GFA-535s. Curious as to how your Cit-12 compares to those.

 

[NoTransistors]

The print on the Baldwins is green. They cannot hold a candle to the Telefunkens that I am using now.

 

[gadget73]

I believe those are Sylvania. I have a couple myself. They may not be Teles, but they're not utter trash either.

 

[BillWojo]

Gordon, a few months ago I picked up a set of Mac MC40 monoblocks and a tube friend of mine electrically restored it using a kit supplied by Jim Mcshane. All the smaller signal tubes are good vintage Telefunkens except for the 12Bh7's, I believe they are RCA. The main power tubes are 6L6GC's and I'm using a set of vintage GE's that tested very good. Have a spare set of RCA blackplates that tested very good as backups. And I'm always on the look out for more spare tubes. I think your correct that 6L6GC's will be around for a long time. I'll be long gone before they run out of them. Was talking to my brother the other day, an accomplished guitar player and he was telling me about a really sweet custom tube amp that he picked up. Main tubes? 6L6GC's. I know he would love to try out my RCA's. Anyway, I think that was good advise.

BillWojo

 

[arts]

Some of the JJ's have been pretty good for me. I've had excellent results with the E34L in all applications. The EL84 is good in home audio,but not so great hanging behind a pair of 12's in an AC30 on 10! All of the 12AX7-type models have all been fairly quiet and non-microphonic. On the other hand,the 6550,KT88 and 5AR4 have all been problematic for me,and I will never use or recommend them again. The 6L6 and 7027 models are a real head scratcher: Some crap out really quickly in undemanding applications,others have lasted for a very long time in what I'll refer to as ''torture-amps'',such as the Ampeg VT-22 & VT-40,played at high volumes on an ongoing basis.
Go figure!

In the end,it seems that certain JJ models are better designed,manufactured,or scrutinized for quality than others. Kinda makes for an expensive crapshoot....

Art

 

[whoaru99]

Never had an issue with a JJ can cap (dual section). I use them interchangeably with F&Ts, no sweat.

Regards,
Gordon.

Had some JJ dual section can caps in a previous amp. No trouble with them.

However, when I rebuilt the Victor MST-30 I used F&T dual section can caps. Best as I can tell, the F&Ts are rated 5000 hours @ 85C whereas the JJ cans seem to be rated 1000 hours @ 70C.

 

[GordonW]

It all depends on how hot the caps get.

In many solid-state-rectified amps, there's no tube near the supply caps- so they last a LOT longer, than if they were near 70C all the time.

If I were parking them near a big rectifier tube, I'd probably use the F&Ts, or even something with a 105C rating (if possible).

Regards,
Gordon.

 

[gadget73]

Placement of old filter caps was definitely shaky at times. The ones away from heat also do usually hold up better. I just brought up an all-original Sherwood integrated from 1963 last night, and all the caps seem to be OK in it. SS rectifiers, and the caps are all away from any major source of heat. The ones in the Sherwood receiver were toast when I got it, and they live jammed between the hot power transformer and the back side of the very hot tube shield.

 

[Hi-Q]

All Russian and Chinese tubes have a long time traveling through the post so all kinds of internal damage can get realised. I chose JJ KT88's as their glass envelopes are stronger than some other makes and I never had a loss of vacuum fracture with them. Both I and two friends run them and we have had only one real failure due to an intermittent screen grid failure causing B+ fuse to blow. However we have had the odd JJ KT88 'let go' where hum has appeared on one channel of our amps with the accompanying red plating. But I consider this to be more of a problem with our amplifiers, we all run Yaqin 100b amplifiers, whose sockets leave a lot to be desired. Once retention-ed the fault goes away until next time, usually some months later. I have however noticed a Black ring appearing around the Control Grid Pin and this may be due to oxidation due to dissimilar materials between tube pin and socket. It takes a lot of cleaning to remove this Black ring, after which I coated the pin with a very fine solder covering where the Black ring was originally formed. The jury is still out as to whether this will stop what could be the problem but needless to say, a set of high quality Gold turned pin sockets are waiting in the spares drawer for trial if this problem re-occurs. But I am going to stick with the JJ's as they do sound good and while I have them the frightening Glass popping is no more.

 

[thorpej]

I must also respectfully disagree here, regarding multi-section caps. There is no inherent reason why they must be inferior. But back to topic, as said in a previous post: I have used dozens of JJ 50+50µF-500V and 100+100µF-500V caps over more than 20 years and never had a single problem (also always measured each one for capacitance, leakage etc.). Construction is necessarily more expensive; depends on what mounting flavour you want.

(Not that I have not also successfully used other makes like Hitano, Panasonic, Nichicon and Philips. But the question was regarding JJ - and those JJs come in 500V; most others are rated 450V.)

Indeed, I also love the JJ can caps, although I tend to run them quite below their rated value of 500V. I am planning to build an amp using their 350uF 385V cap soon on a power supply that will have 350V or so coming out of the (solid state) rectifier, so that will give me a taste of their reliability when run closer to their voltage rating.

 

[onwardjames]

And to think, my guitar amp tech told me specifically to replace my groove tubes in my Fender Bandmaster that he restored (one is occasionally fiddly, gets noisy) with some new 6L6 JJ tubes. Haven't done it yet, and probably now won't.

 

[Pio1980]

And to think, my guitar amp tech told me specifically to replace my groove tubes in my Fender Bandmaster that he restored (one is occasionally fiddly, gets noisy) with some new 6L6 JJ tubes. Haven't done it yet, and probably now won't.

Talk to him about that, the 6L6 line may be OK and better in his experience.

 

[guitarslam]

Update / revival to this thread.

I routinely purchase & hold tubes before using them. Several of my guitar amps use EL34 power tubes. JJs (KT-77, EL34L) are the only EL34 tubes I seen fail right out of the box. In fact, they're failed in the box too! One EL34L and another, KT-77 went gassy while in storage.
On closer inspection of the glass, I've noticed small, short cracking near the base on each of the faulty tubes.

I've have good success with their 6V6s, EL84s, and 6L6s, but I won't be using their EL34 products in the future,
It's better to spend a few more bucks than to risk damaging my amps.

 

[slimecity]

The only time I've had a fireworks display that could have resulted in a house fire was from a UK kit amp with 4 x JJ EL84 tubes - one failed, taking out a few nearby resistors.

Havent touched JJ since -mind you, this happened about 15 years ago, things may have improved since then

 

[KlipschFan61]

I had one tube from a supposedly 'matched' a pair of JJ 6SN7 input tubes flare at the base. Sent them back to TD for a replacement pair that haven't left the boxes.