Early tube mortality

[Little Pigbacon]

How common is it for a new tube, burned in twenty-four hours by the tube vendor, to head south after just a couple hours' use, redplate, and take out the tube next to it as well? Tech reports nothing else wrong.

I'm asking for a friend.

 

[Boogie Bill]

Re: Early tube mortality

When I bought my blonde Mark III 112 EVM combo, I re-tubed it with a set from www.thetubestore.com. It really sounded great.

A couple days later, I take it down to a local bar for a weeknight blues-rock jam session, hosted by some of the area's top musicians. First song, no problems. Second song, I launch into "Black Magic Woman" and about half-way thru the opening solo, the amp starts making funny noises. I'm trying to sing, and the amp is going, 'woo-AH-EEEEEeee-ooo-OOOWWWWeee". Making Yoko Ono noises, even with my guitar off. I finally reach down and shut it off. Half the audience is going, "WTF?!", and giving me rude looks, and the coked out musicians are going, "Man! What a cool effect pedal!"

I was just SO embarrassed! And being new in town, it did NOT help establish my reputation as a great singer/guitarist/songwriter!

After slinking home with my tail between my legs, discovered that the Brand new E-H 12AX7 in V1 had shorted. Tubestore was great and sent me a replacement ASAP, no problem, with apologies.

It does happen. I carry spare tubes to a gig, and have for years. But at a jam where you only get to do two or three songs...S-C-R-E-W-E-D!

It does happen. I feel your buddy's pain, believe me. All you can do is buy good tubes from a reputable vendor who will back them with a solid warranty.

Oh...and I never went back to that jam, LOL! When I did decide to go back, they'd gone out of business!

IT'S NOT MY FAULT!!!! (LOL!)

Bill

 

[Edgecrusher]

Re: Early tube mortality

With modern production tubes its not so rare. particularly with El84's. In my experience around probably 1 in 24 (From a GOOD vendor) will have a premature death of this sort. Tube quality is real hit and miss.

 

[Joey Voltage]

Re: Early tube mortality

I would agree. It's not particularly uncommon, and the traumas that can occur during the shipping process also are not exactly the friendliest either.

 

[IM4Tone]

Re: Early tube mortality

I've been having problems w/ EL84's in my newest amp (Delta Blues 115). Shortly after receipt of the amp (3 to 4 months) one of the EL84's lost it's vacuum and failed (the glass detached). Replaced it and the one next to it. Several months later one of the El84's redplated, so I installed a new matched quad. Now, six months later another redplated, so I took it to a highly reliable tech to be checked. Is it faulty tubes, the bias too hot, or something else in the circuitry?????????????? I'll find out this week or next at the latest. Never had any issues with any of my other tube amps.

For sure, the first incident was a defective EL84 tube, but the rest....to be determined.

 

[Jacew]

Re: Early tube mortality

Many (most?) EL84 amps are designed after Vox AC circuitry, that does drive tubes very hot for their specs.

 

[Joey Voltage]

Re: Early tube mortality

I've been having problems w/ EL84's in my newest amp (Delta Blues 115). Shortly after receipt of the amp (3 to 4 months) one of the EL84's lost it's vacuum and failed (the glass detached). Replaced it and the one next to it. Several months later one of the El84's redplated, so I installed a new matched quad. Now, six months later another redplated, so I took it to a highly reliable tech to be checked. Is it faulty tubes, the bias too hot, or something else in the circuitry?????????????? I'll find out this week or next at the latest. Never had any issues with any of my other tube amps.

For sure, the first incident was a defective EL84 tube, but the rest....to be determined.

If it's a Peavey (I'm assuming), You may be able to rule out a "hotter" bias. Peavey typically uses a non adjustable fixed bias in most of those models factory set at -14v which is fairly cool for el84's unless of course somebody tried to make adjustments which is entirely possible. Is it the same valve position that starts to red plate every time, or different? Does it follow the tube, or socket?

 

[IM4Tone]

Re: Early tube mortality

If it's a Peavey (I'm assuming), You may be able to rule out a "hotter" bias. Peavey typically uses a non adjustable fixed bias in most of those models factory set at -14v which is fairly cool for el84's unless of course somebody tried to make adjustments which is entirely possible. Is it the same valve position that starts to red plate every time, or different? Does it follow the tube, or socket?

Yes, a Peavey Delta Blues 115.
Got the amp new, so it's bias was set by the mfg.
The first redplate was V5, the second V7. Doesn't follow the tube, since it was replaced.
I'm hoping to find out this week???
Puzzling so far.

 

[Joey Voltage]

Re: Early tube mortality

Yes, a Peavey Delta Blues 115.
Got the amp new, so it's bias was set by the mfg.
The first redplate was V5, the second V7. Doesn't follow the tube, since it was replaced.
I'm hoping to find out this week???
Puzzling so far.

Typically when the red plating stays with the socket, for example if you rotate the tubes around, but the one that's always placed in the second socket always redplates, is when you may have something in the peripheral causing it. If the red plating moves with the tube - if the same tube redplates in each socket, it's usually just a defective tube. Sounds like its most likely just the latter.

 

[IM4Tone]

Re: Early tube mortality

Typically when the red plating stays with the socket, for example if you rotate the tubes around, but the one that's always placed in the second socket always redplates, is when you may have something in the peripheral causing it. If the red plating moves with the tube - if the same tube redplates in each socket, it's usually just a defective tube. Sounds like its most likely just the latter.

My suspicion as well.

 

[IM4Tone]

Re: Early tube mortality

Yes, a Peavey Delta Blues 115.
Got the amp new, so it's bias was set by the mfg.
The first redplate was V5, the second V7. Doesn't follow the tube, since it was replaced.
I'm hoping to find out this week???
Puzzling so far.

Picked up the amp today. The tech said there was an issue in the circuitry AND 'bad' tubes. So I asked which caused which and he said it started with the bad tubes. I had nine EL84's from the original plus the replaced defective one plus the 6 month old quad that I bought. He tested them and said only two would meet his standard and so two new ones added, circuitry repaired and bias checked and adjusted.

So to address the OP's original question (at least in part) there appears to be a lot of sub-standard new tubes, although the ones I bought were not claimed to have been 'burned in twenty-four hours by the tube vendor'. The originals in the new amp had failures; the new ones I bought also had failures. I purchased them off ebay and price shopped, but now I will pay a bit more from a supplier that tests 100% and was recommended by the tech I use. It is his source for his stock. I really don't care to provide names of the good nor the bad from this experience.

He happened to show me a very old Supro that was on his bench. I think he was replacing the speaker. The tubes were originals so that's 50's 60's era. They're not making tubes like they used to.

 

[Darg1911]

Re: Early tube mortality

6P14p-eb/ev

 

[IM4Tone]

Re: Early tube mortality

6P14p-eb/ev

 

[beaubrummels]

Re: Early tube mortality

He's talking about the Russian version of the EL-84. Supposed to be strong, reliable, long lasting.

http://www.jacmusic.com/nos/6P14P-EB/

https://tubes-store.com/product_info.php?products_id=20

https://www.thegearpage.net/board/index.php?threads/reflektor-6p14p-tubes.1294430/

 

[Darg1911]

Re: Early tube mortality

He's talking about the Russian version of the EL-84. Supposed to be strong, reliable, long lasting.

http://www.jacmusic.com/nos/6P14P-EB/

https://tubes-store.com/product_info.php?products_id=20

https://www.thegearpage.net/board/index.php?threads/reflektor-6p14p-tubes.1294430/

Yes sir. I bought a couple of matched quads from an Eastern European seller (from Bulgaria I think), probably 15 years ago now. They were for a Scott integrated amp that took 7189's and the tech that worked on it warned not to expect much longevity from new production EL84's. The old tubes were shot and the tech replaced with current production tubes that his experience told him had the best shot of surviving the longest ... with the warning to make sure I have spares on hand. I cant recall what they were. I don't think Sovtek was making the EL84M yet. At any rate, I installed a quad of the 6p14-eb, biased and those same tubes are still going strong. That old amp ran the plates at 420 volts, plus. Higher with the higher, modern day line voltages.

There are still plenty of sellers overseas selling those tubes. I cant speak for the quality of what is left now, 15 years later, or any particular seller. But, the ones I bought back then were closely matched and durable as hell. At least the quad that's still in that amp. I still have the spare quad but haven't had to use them yet.

Point being, if longevity of EL84's is a problem/concern, those 6P14-eb/ev's are still cheap enough to be worth trying.

 

[IM4Tone]

Re: Early tube mortality

Yes sir. I bought a couple of matched quads from an Eastern European seller (from Bulgaria I think), probably 15 years ago now....................Point being, if longevity of EL84's is a problem/concern, those 6P14-eb/ev's are still cheap enough to be worth trying.

During my latest incident, we discussed the best EL84's currently available. The tech commented on how good the Russian ones used to be, but added 'not so with current production from Russia'.

 

[6p5p]

Re: Early tube mortality

How common is it for a new tube, burned in twenty-four hours by the tube vendor, to head south after just a couple hours' use, redplate, and take out the tube next to it as well? Tech reports nothing else wrong.

I'm asking for a friend.

It sounds like way too hot biasing. It can burn the best new tube within few hours.

Sent from my GT-N7100 using Tapatalk

 

[Little Pigbacon]

Re: Early tube mortality

It sounds like way too hot biasing. It can burn the best new tube within few hours.

Sent from my GT-N7100 using Tapatalk

I don't know. I had it at 34mA per tube. I got that from the actual plate voltage plugged into the Weber bias calculator. The tech scolded me for using socket savers for tube rolling, but he didn't say anything about bias levels.

 

[6p5p]

Re: Early tube mortality

I don't know. I had it at 34mA per tube. I got that from the actual plate voltage plugged into the Weber bias calculator. The tech scolded me for using socket savers for tube rolling, but he didn't say anything about bias levels.

How much is the plate voltage there? Proper biasing is dependent on that detail...

Sent from my GT-N7100 using Tapatalk

 

[Little Pigbacon]

Re: Early tube mortality

How much is the plate voltage there? Proper biasing is dependent on that detail...

Sent from my GT-N7100 using Tapatalk

I don't remember, but I might have it written down somewhere. I remember it took a little while to stabilize after I took the amp out of standby, so I let it do that before I tried to do anything with it. I remember the Eurotubes meter got the same result as their probe used with my DVM.