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6C33C-B Failure Mode?
6C33C-B Failure Mode?
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Old 30th June 2005, 06:58 PM   #1
Alastair E is offline Alastair E  Wales
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Default 6C33C-B Failure Mode?

Providing the heater connections on sockets are well made and checked periodically, are there any particular failure modes of the Russian beast?--Any advice on maybe slight heater starvation, to lengthen life?

Currently running 3xSE, with plate diss at around 47W, Well within ratings.

Planning on an OTL, when I get round to it........
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Old 30th June 2005, 07:37 PM   #2
Colt45 is offline Colt45  Serbia
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I remember, from a long time ago,

data sheet mentions using half the heater (the heater is center tapped) and 75% of the dissipation..

but I cant imagine it working very well for OTL.. you need as much perverance {or whatever you call it} as you can get.
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Old 1st July 2005, 10:14 AM   #3
Alastair E is offline Alastair E  Wales
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Default Interesting!

Colt 45-
I thought the 6c33c-b, was the valve of choice for the home OTL builder..........

From my (limited) research into the valve, It would appear to have a high 'pervayence'-(Current Capacity??) as its designed for series reg work in silly things like Mig 29 fighter aircraft

Ive been out of tube experimenting for a few years, and have recently (around a year or so) become interested in it again--Yes, the bug bit again--Guess when you get infected, its re-occuring!

Could you tell me why you think the 6c33 aint no good for OTL, and what would you use instead?--Ive got around 10 nos PL 509's and 8 new 6c33's

The 6c33 looks to be built like a first world war battleship in comparison to the '509, and has a greater peak current capability, all be it with a hugely hungry heater
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Old 1st July 2005, 11:11 AM   #4
barretter is offline barretter  United Kingdom
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It's "perveance" chaps. Regards, your local pedant.
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Old 2nd July 2005, 08:03 AM   #5
tubetvr is offline tubetvr
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Colt 45- I thought the 6c33c-b, was the valve of choice for the home OTL builder..........
I think that Colt 4 was only refering to the practice at running the 6C33C at half heater and with limited dissipation which I agre it is not a good idea, it is much better to use it flat out.

I have quite long experience of using 6C33C in both OTL and SE amps, I have used the same 4 tubes in my OTL amp for now almost 5 years and although I dont use the amp daily but maybe every 2nd day I usually keep it switched on for a whole day or at least for several hours every time. I have also made copies of the same amplifiers for some friends of mine and they neither had any tube failures.

What is then the secret of long life? I think the most important is to use a sensible power dissipation, not more than 40W, (Viktor at BAT also reports that this is very important for long life).

2nd most important is burn in, it should be done like this:

Run tube on heater only for at least one hour.
Then run the tube for at least one hour with fixed bias and reasonable anode dissipation, not more than 40W.

3rd important, run tube on heater at least 30 seconds before applying anode voltage.

4th important, use good quality sockets, preferably real russian ones, I never had a problem with bad connection in the sockets.

5th most important, use a good tube supplier, buy directly from Russia, from GS tubes or tubes.ru, then you know that you get the real stuff and not some rejects.

I had only one tube failure in spite of using ~40 tubes and that was one tube that had a cathode grid short when taking it out of the box.

BR Hans

PS, dont starve the heater, it is not the heater that goes first, it is very unusual that heaters burn out, instead starving the heater will only shorthen the life of the cathode and will reduce the emission and Gm of the tube, this is valid for any power tube. DS
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