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Burned out power tube

fauxpas

Member
2007-11-15 3:09 pm
I have replaced the chinese 6P3P tubes with 6L6GC tubes of various designs. I recently picked up some 6P3S-E reflektor tubes and they sounded great for all of an hour before one burned out. Interestingly, it was the one of four that was from a different batch as it had slightly different markings. The reflektor logo was bigger etc.

Is it likely just a dodgy tube? Or are there enough differences between the 6P3P and 6P3S-E to not use the 6P3S-E again?

They were these common ebay tubes.

[IMGDEAD]http://www.rutubes.com/description_foto_ebay/tubes/6P3S-E1-4.jpg[/IMGDEAD]
 
Funny that. Same thing happened me last night with an EL84. I was the far side of the room. Amp was on, bias was stable and voltage to the screen was spot on. Heard a crackle through the speakers and it had burnt before I could get back to the power switch. When I took the tube out there was a crack in the base of the tube. Whether that caused the problem, or was caused by the problem I couldn't guarantee but they had been working OK up to that. These tubes have been physically roughed a good bit, in and out loads of times etc.

Tube glowed bright, almost white (amp upside down and could see the glow through the centre of the socket) Burnt a screen stopper as well.


Never had it happen to me before, so it was a bit of a shock!


Fran
 

kevinkr

Administrator
Paid Member
woodturner-fran said:
Funny that. Same thing happened me last night with an EL84. I was the far side of the room. Amp was on, bias was stable and voltage to the screen was spot on. Heard a crackle through the speakers and it had burnt before I could get back to the power switch. When I took the tube out there was a crack in the base of the tube. Whether that caused the problem, or was caused by the problem I couldn't guarantee but they had been working OK up to that. These tubes have been physically roughed a good bit, in and out loads of times etc.

Tube glowed bright, almost white (amp upside down and could see the glow through the centre of the socket) Burnt a screen stopper as well.


Never had it happen to me before, so it was a bit of a shock!


Fran

I've had that experience a few times with EI KT90's and JJ KT88, at 500V and above the experience is quite spectacular - and quite unwanted..

In the case of KT90 which developed internal shorts internal components vaporized instantly resulting in a fractured envelope - and in one case the envelope actually exploded, both the screen and cathode feedback resistors simultaneously burst into flame. A cap bank equivalent to 1000uF charged to 525V packs quite a wallop, hehe.. :hot:
 

tubewade

Member
2007-06-03 8:54 pm
I would say that it was not due to the fact that the valve was an "E" version, but rather that it was simply bad from the beginning. If it worked fine with chinese valves to start with it should work fine with these, providing, of course, that they aren't defective.

Wade
 
They look like like the same tubes that Sovtek uses for their 5881/6L6WGC. They're mediocre quality, even though many guitar amp manufacturers use them. I have used Sovtek 5881 tubes in one of my hi fi amps, but was never quite happy with the sound. If you received these tubes at a super low price, I'm sure they weren't completely tested and "weeded out" before they left the plant. Your best bet would be to run everything through a tester before putting them in your amp. (But that won't cover everything, like catastrophic failures).
 
Perhaps with so much rebranding going on with the Russian tube market, this is the right time for someone knowledgable to give us an update where which tube version is made by whom ? It is confusing.

Personally, I've always avoided the Sovtek brand (the logo with the pigeon) as I find them notoriously inconsistent. That is both signal and power types.



richj
 

fauxpas

Member
2007-11-15 3:09 pm
I have been obsessed with sourcing generic russian tubes lately.

Primarily reflektor and voskhod tubes.

Net sources indicate to me that the reflektor plant in Saratov manufactures svetlana tubes, or did.

Before the tube popped, I must say I was impressed and am sourcing more from a different person. I found the reflektor and voskhod pre amp tubes very nice too in 6N1P and 6N23P guise...

So far, I have auditioned 1 x chinese, 2 x USA and 1 x russian 6L6 variants in my amp, and the 6P3S-E russian tubes easily sounded the best. They sounded the fullest, while others had incredible clarity at the top, the 6P3S-E felt great through the entire frequency range.

REFLEKTOR-SARATOV
reflectr.gif


VOSKHOD-KALUGA
voskhod.gif
 

tubewade

Member
2007-06-03 8:54 pm
I wouldn't define myself as highly knowledgeable, but I have used a few Russian valves so I can relate my experiences in case they are helpful.

My first set were sold as Sovtek 6L6GC, but they are actually 6p3s. They are still in service. They sound OK but are not able to handle high voltage or great dissipation. Treat them as a 6L6GA and they will last. I'm using them in in an old amp that called for 6L6G.

I've also used several set of Sovtek 6L6WXT+ and not had any problems. I've had them in my Heath W5s for a long time and they function perfectly. They will replace 6L6GCs, 7581s, 7027As and KT66s in everything I've tried them in.

I've purchased several lots of OTK 6n14n and 6n14n-eb to match some quad sets for my own use and have found these to be excellent quality. They are heavier than their NOS counterparts. Out of probably 60 or so that I have purchased only two have tested less than perfect on the tester and even these work perfectly in an amplifier. No failures. No problems.

My experiences may be atypical from what I've read but I have been satisfied with the Russian valves I've used. I believe all of these were manufactured by Reflektor.
 
Regarding brands and tube longevity, this 1950's KenRad version of 5U4G is by far my longest service tube in current use and has outstripped 45,000 hrs service mark and still with good emission.

Where did the Ken Rad brand originate from ? Did it have
it's origins in Canada ??

richj
 

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Shoog

Member
2002-08-15 10:16 pm
Eire
I have had some 6H13C from Russian, there is no brand written on them but there is a circular logo with a C on it and wings to the circle.
I have also had some 6O3n (russian ECL82's) from the same manufacturer.
Quality has been good and consistent. I have found them to be softer sounding than the NOS equivlants I have come across. Good but not exciting.
Who is the manufacturer??

Shoog
 
Shoog said:
I have had some 6H13C from Russian, there is no brand written on them but there is a circular logo with a C on it and wings to the circle.
I have also had some 6O3n (russian ECL82's) from the same manufacturer.
Quality has been good and consistent. I have found them to be softer sounding than the NOS equivlants I have come across. Good but not exciting.
Who is the manufacturer??

Shoog

Hi Shooq,
From the description of the logo those are likely to be Winged C, AKA Svetlana anywhere except in the United States where New Sensor currently owns the rights to the brand name. They're made in St. Petersburg by Svetlana SPb..

Because the joint venture company SED - Svetlana Electron Devices based in Huntsville, Alabama went bankrupt some years ago New Sensor was able to acquire the rights to this name for use in the USA in the ensuing liquidation sale. This makes buying Svetlana SPb tubes here a bit more difficult as you have to be very careful to make sure you are actually getting =C= branded tubes.
 
Colt45 said:
"Kentucky Radio"

Kenrad started making tubes in 1925, and apparently was acquired in 1945 by GE. The company was divested in 1987 when GE and RCA merged. They still make specialized microwave tubes.

Their tubes are generally well regarded.

I have some very nice box plate 2A3 made by Kenrad, somewhat before the acquisition. Their construction style is uncommon here, and I don't know of any others that are exactly the same. They command princely sums on eBay these days..

Here is a site with some useful tube lore and a little information on Kenrad (where the information posted here came from in fact.)

http://telecomottawa.net/~cmacd/tubes.html
 

Shoog

Member
2002-08-15 10:16 pm
Eire
Because the joint venture company SED - Svetlana Electron Devices based in Huntsville, Alabama went bankrupt some years ago New Sensor was able to acquire the rights to this name for use in the USA in the ensuing liquidation sale. This makes buying Svetlana SPb tubes here a bit more difficult as you have to be very careful to make sure you are actually getting =C= branded tubes.

Mine came out of Estonia, so I would say they are the genuine Russian article. Thanks for the info.

Shoog