Anyone Else Have Trouble With JJ Tubes?

Azriel

Azriel

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Hey guys,
I've been shopping for a used tube amp, and it seems like every time I find an amp I'm interested in, it's got those blasted JJ tubes in it. So far, I've passed up a beautiful Cary, Conrad-Johnson, and ARC amp, all because they have JJ tubes in them, and the price wouldn't support throwing them in the garbage (the tubes, not the amp) and re-tubing with real tubes.

Why all this animosity you ask? Maybe I'm unlucky, but so far, literally every single JJ tube I've bought has failed in very short order, some dangerously. I can remember a lovely Marshall clone guitar amp whose front end was destroyed when a preamp tube randomly shorted out. I've lost countless power amp tubes (6L6, EL84 and EL34) in hifi amps, guitar amps, and PA amps. It seems to be the same phenomenon. Preamp tubes will be fine for days (usually last under a week) and then suddenly POP! Followed by a loud buzz and it goes dark. Like a light bulb that burned out. Usually if I look close I can even see burn marks on the glass. This on several amps.

The power tubes seem to be less violent, just very short lived, won't hold bias, get noisy, etc. I had a pair fail in a completely perfect Marshall JCM 800 in under 3 days, while a set of Siemens (beautiful tubes) lasted for years. Same with a neat old Knight hi-fi amp I used to have.

So my question is this: am I unlucky, or are JJ tubes just crap? I've noticed they're extremely cheap to buy, and figure there must be a reason for that. I guess I'm just used to buying quality tubes and having them last for years, so I have no tolerance for early failure.

I'm frustrated by how many sellers seem to throw them in an amp just to sell it, and advertise "New Tubes". They don't tell you that the tubes are basically garbage. I'm really looking for a tube amp that actually shows some pride of ownership.

Anyway, rant over..LOL. Guess my gripes are two fold tonight- cheap tubes, and their proliferation among amps for sale. Guess the seller's keeping the good tubes for himself!

-Jon
 
Some amps, often guitar amps, and some vintage audio amps run the tubes really hard. Seems like old tubes could take a bit more.

Specifically though, I have a quad of JJ EL84 in an amp I just rebuilt. They're running 325V net on the plates @ 28mA. So far so good, but it's only been about a week. :)
 
If you're losing JJ PREAMP tubes that fast, then I'd recommend having the amp checked out. Sounds like heater voltage is out of spec!

I've seen LOTS of JJ power tube failures- but almost no preamp tube failures. And I'm around a lot of guitar amps- I see stuff that's just been HAMMERED, on a regular basis...

Regards,
Gordon.
 
I have no problems with JJ tubes, of a 1000 sold 4 has come back to me the last year. A few has been
returned by me during my ac ceptance test. Maybe the reason is that i buy direct from the factory and
noone has been rejecting these.
 
Az, that is too much coincidence.

Understand tubes. You know obviously that they have a cathode, heated by the filament, and a plate. They will have X amount of grids and whatnot in between depending in the tube type.

So, what can go wrong with a tube ? Well if it isn't 35 years old and tired, failures are caused by a couple of different things. One is that it has gas. Of course they strive to get a real vacuum in there, but unbeknownst to most people, everything dissolves in everything. There is gas dissolved in the metal elements of that tube. They know it and they bake it to get rid of that, and then they spray some kind of osmium based stuff in there that will absorb the gasses from the elements as the tube works and ages. Actually they bombarded cathode ray tubes with high power RF in a chamber to loose up those gases from the elements because that greatly affect the life span of the expensive CRT. This is a much smaller scale and I doubt they bombard "receiving" tubes, which is what they all are except CRTs and transmitter tubes. Yup, those 6550s and 6L6s are "receiving" tubes even though they are high power amp tubes.

There are a couple of factors to consider here. One was already mentioned - that some manufacturers pushed the tubes too hard. Some of them said to only use tubes from them. That is because they got special speced tubes from someone and THEIR 6L6 can handle 610 plate voltage but the regular one cannot.

And then, with all tube equipment we got another problem. Line voltage in the US used to be 110 volts. Now it is 125. Let's do the math. Let's just figure an arbitrary impedance, ten ohms.

For 110 volts you get 1,210 watts in ten ohms.

For 125 volts you get 1,562.

Now really, as an engineer charged with bringing out the product at the best price, and devices that can handle 1,500 watts instead of 1,200 watts cost considerably more, what do you do ?

And when it comes to old equipment they could not forsee this. Line voltage was 110 volts, that is all they knew.

In the long run, the getter should tellya.
 
I read years ago about JJ power tubes having problems and Jim's avoidance of them based on his testing of boxes of tubes he buys and having to return a higher percentage of them. For this reason, I avoid JJ tubes but then I have enough to last a while and am not actively looking for any tube gear.

I find it odd that the purchase of an amp at a price can't support the disposal of the tube set and replacement with good tubes. Maybe the OP is looking for some multiple power tubed amps where a new set would be hundreds of dollars.
 
Another reason tube gear is sold with cheap tubes is that many tube enthusiasts have their own "flavor" of tube that they prefer, so whoever buys it is just going to put the particular brand of tube they like in it anyway.
 
When I was looking at ordering JJ EL84s, I seem to recall McShane giving them a blessing of sort. From his website -

6BQ5/EL84 JJ, one of the good JJ tubes, in stock, burned in and carefully matched. $xx.xx ea., $xx.xx/pair, $xx.xx/quad.
Click to expand...

OTOH, EL84 is but one of many.
 
I won't use JJ's in my guitar amp rebuilds. They hum wildly in many Fender's and have short lives.
I use Electro Harmonix exclusively. Rarely have any problems with them and they sound great!
 
The rectifier tubes in my Heathkit UA-1s are the original tubes, almost black with age, but still working. JJ replacements arc and fail within hours or days, which is why the original tubes remain.
 
Several years ago Jim McShane issued a warning that he was having reliability issues with octal based JJs tubes. I don't know the situation today but if you ask Jim he will give you a straight answer. The EL84, 300B and 2A3-40 continue to be very reliable. I don't use any octal based JJ tubes, but my JJ 300Bs have been reliable for a decade and my favorite tube, the JJ 2A3-40, has been chugging away for years at Ep = 300V, Ip = 65 mA.
 
I run JJ 6L6GC's in 3 of my MC240s as 'everyday tubes'. They are competent and I haven't had a problem with any after hundreds of hours on two of the sets. But, mac's don't run them hard.
 
Palustris said:
Several years ago Jim McShane issued a warning that he was having reliability issues with octal based JJs tubes. I don't know the situation today but if you ask Jim he will give you a straight answer. The EL84, 300B and 2A3-40 continue to be very reliable. I don't use any octal based JJ tubes, but my JJ 300Bs have been reliable for a decade and my favorite tube, the JJ 2A3-40, has been chugging away for years at Ep = 300V, Ip = 65 mA.
Click to expand...

That's kind of my general experience, too. JJ EL34s didn't hold up, JJ 7591s are absolute junk, IMHO. JJ 6L6s aren't categorically horrible, but they weren't as reliable as Shuguangs or the Ruby MSTRs (also Chinese).

JJ EL84s work fine- they just don't last as long under hard use (like in a Vox guitar amp or the like) as the Russian-made ones.

Regards,
Gordon.
 
I remember reading, a while ago, that the JJ 7591s were actually pretty good power tubes if they make it past the first 100 hours. It seems that if they are going to die, they do it early.
 
Life's to short to mess with JJ tubes, at least that's how I see it. I can feel the OP's pain too, I hate it when people yank an amps tubes, then either sell it no tubes, or with trash tubes. I can think of lots of instances where the tubes are worth as much or more than the amp. First that comes to mind is the old Fisher boxcar amps that used Mullard EL37s as outputs. Call me goofy, but if I couldn't run the EL37s, I'd just wait until I could and listen to something else instead of listening to an AZ80 with 6L6s in it. :dunno: Heck even less expensive integrateds can fall into this category. Take a Fisher, Sherwood, Scott, whatever, that has 7 Telefunken 12AX7s, and four Westinghouse 7591s, not to mention the 12AU7s and maybe a 5AR4 rectifier. You can get to 1000 dollars in used ebay tubes pretty quick. It's like old cars or whatever, I'd rather have it in "barn find" condition even if a couple tubes are bad, than have something someone took the tubes out of so they'd make an extra couple hundred bucks or so, especially if you get into tuners or amps that have bias and balance controls. Of course people can sell their stuff however they want, it's the buyer that has the money control. The amps the OP mentioned, if maintained and set up properly, would still be on their original tubes anyhow.
 
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