Is this describing a blown tube, or two blow tubes?
I installed a new set of JJ e34’s a few days ago. Last night there was a very loud POP and one of the tube went bright so I moved quickly and turned of the midmonos.
After they cooled I inspected the tubes and they seemed fine so I reinstalled them thinking maybe it was some kind of impurity within the tube. I’ve never experienced a blown tube before.
The amps ran great this evening until just now, and another POP and bright tube, but it seemed like it was the other tube, but I can’t be sure. This was followed by a low whistle or hum and I turned the amps off again.
Is this simply a run of the mill faulty tube? Could two blow in one day, or could the first one POP like that and then continue to work for another day?
Since Ive never experienced a tube fail before, could this have anything to do with the Amp, or is it just a bad tube or tubes?
accurate 151 (I have 157, gave my friend 257, gave another friend my bigger heavier, thus less portable Hickcok (it always/still does agree with my little 157).
2. One blown, DO NOT use the equipment until blown tube replaced. More than likely 2nd tube was ok till you blew it.
3. IF only 1 blown, get a new matched pair, keep the good one as a spare untill your new matched pair arrived.
If/when a tube eventually weakens or blows (most last thousands of hours, but I check all mine, with my little tube tester, preamp and amp, bi-annually).
4. IF, again, a tube blows too soon, there is something wrong with the amp.
5. Test matched tubes you buy, test tubes when a system problem occurs, to avoid guessing.
Last night there was a very loud POP and one of the tube went bright so I moved quickly and turned of the midmonos.
The amps ran great this evening until just now, and another POP and bright tube, but it seemed like it was the other tube, but I can’t be sure. This was followed by a low whistle or hum and I turned the amps off again.
"Bright tube"... RED PLATING?
Does the amp auto bias the power tubes or does the user have to manually adjust the power tube(s) bias?
I wouldn’t take a chance with the JJ e34 power tubes now. If they did Red Plate they more than likely are done for. It is possible circuitry may be damaged in the amp as well. You may need to have a Tech check out the amp.
OUTPUT TUBE BIAS SETTING
Output tube bias should be set immediately when new tubes are put in; then again in 15 minutes;
and periodically the first few times of using the amplifiers. After that the bias should be checked
monthly.
The bias controls are located between the output tubes near the power and output transformers
To adjust the bias you will need a slot-head screwdriver. Adjust by turning clockwise to increase
bias; counterclockwise to decrease bias.
could also be small particles left over from manufacture that get into the plates tapping the tubes with a screwdriver handle, quite hard too, obviously not too hard to break them. may dislodge the particles. roll the tube around a bit in your hand to see if you can see hear anything moving around inside the tube. its not uncommon to find small bits left over inside the tube these can get into the plates when in shipping for example.
That is what I thought at first since the tube still worked. The second time there was a whistle, so certainly different.
I emailed mike sanders last night and he said it sounded like a normal tube failure and that a failed tube can work for another day until the failure is complete.
Before installing new power power the bias pot(s) should be turned back (turn the bias pot(s) counterclockwise), so as to not over bias the new tubes. Not doing so can damage perfectly good new tubes.
"Output tube bias should be set immediately when new tubes are put in; then again in 15 minutes;"
Did you do this before and after installing the new tubes?
You said you reinstalled the old tubes and the amp works fine. Just a guess the bias setting was still set for the old used tubes. Is that correct?
"Output tube bias should be set immediately when new tubes are put in; then again in 15 minutes; Did you do this before and after installing the new tubes?"
I did both of those things, yes, and Ive checked the old tubes' bias I just put back a few times and they have settled.
Well, Tube depot offered a refund so the quad is heading back today.
I am going to order a quad of GL 77's, but I have to go on vacation which totally sucks when there's music to listen to :-). I will be bringing my portable DSD player, but...
Honestly i virtually always buy a set of tubes and then I dont think about them for many years. I just dont see myself buying a tester, but I do apprecite the time you took for me. Im sure it will help another reader that can findb use for it.
Absolutely, no tester. I have about 30+ tubes in four components. I have an extra set of tubes for each. If something happens, I just swap one for one to find any possible problem. I have had few problems, but this is simple and direct. No reason to buy some ancient device which may or may not work properly, learn how to use it, unless this is fun to you.
The JJ E34L is a variation of the EL34 which is different tube than the "88" (that I assume is a KT88) that you replaced. Specifically, the pentode EL34 has a suppressor grid 3 on pin 1 which a beam tetrode like KT88 does not have. An amp can be made to support both types, but if not, the EL34 suppressor grid could be unattached, or worse used as a tie point for another voltage. I would confirm that your amp is designed for true pentodes like the EL34 family with a suppressor grid 3.
From what you describe I would say it's a typical tube failure if you did not have any problems with the old tubes. Unfortunately, tube infant mortality is quite common as tube factories do not have the greatest quality control, which is why the better tube sellers burn in tubes when they're delivered. But sometimes one just slips through the cracks.
Plug in the old tubes and if all is normal, then get another from Tube Depot. Those guys are one of the best and they'll stand by what they sell.
Also, with push-pull amplifiers a tube tester doesn't offer much practical use. If a power tube can't hold its bias then that is all you need to know to replace the tube.
yes, I always post things that other's as well as OP might find interesting, and finding out about stuff is fun.
I have hundreds of tubes, two of the GE Orange and Gray Porrtable Cases repair men brought to the home, and a few drawers full, a mix of used and new.
I test all my active tubes bi-annually as a matter of course, test any from my drawers of tubes when needed for me or my friends, test my friends tubes, test tubes I order.
Like an inexpensive sound pressure meter, they do not need to be 'calibrated' to give you 'relative' answers. If two tubes show the same strength on the meter, they are in fact equally strong, a bit more or less irrelevant unless close to bad.
My Hickock was calibrated by the tech who sold it to me. My little Accurate 157 always closely matched the Hickock. When I got the Accurate 257, both 157 and 257 matched, I preferred the smaller one because my first wife got it for my birthday way back when. 257 is quite portable as well.
I also have a set of quicksilver mid mono and have lost a tube before. You described my experience to a t. For what it's worth I was running mine with kt120 for a long time until I decided to try the el34 which as I understand the amps were voiced for. My humble opinion is that JJ stands for junk junk. JJ tubes are the only brand that I have bought that were bad out of the box and I have an audio buddy who's experience has been the same. I run my mid mono with Tung Sol and could not be more pleased. I am not sure what they are getting for those tubes now after the embargo but I seem to remember not paying a lot of money for them. I hope this was helpful.
120's ? wow, I didn't think that was possible with MidMonos, I assume you have a more modern version than mine. I have a simpler bias mechanism than I assume you have.
Mutual Conductance Test. (A must for me matching Mutual Conductance of the dual triode sections of a 6922/7308 signal tube.)
Life Test. When a tube tests low good on the meter, or marginal, the life test tells the user how much life is left in the tube or if it should be replaced.
Yeah.. I checked with Mike Sanders when retubing although now you're making me wonder if it was kt150. The tubes I was using went with a pair of prima Luna prologue 6 monos that I sold a few months back. Had them biased at 42 and they were glorious sounding with a fuller lower end but at the cost of some of that mid-range sweetness. I decided I could do with a little less bass for that wonderful liquid mid-range sound. I have used the genelex 12au7 and 12ax7 and found them to be very detailed. I am running a CJ premier 11a now (winged c 6550 and nos Raytheon 6fq7 and 5751s) but work the quicksilvers into the rotation occasionally. Now that I think of it the exception of Kenrad preamp tube the only time I've ever had a tube blow it was a JJ. Have a great night
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