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Old 24th March 2010, 10:59 PM   #1
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Default Plate dissipation specs for 21KQ6

Greetings!
Does anyone have any plate dissipation specs for the 21KQ6/29KQ6 tubes? Believe they also go under LL521. I can't find much data on these tubes.

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Ray
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Old 24th March 2010, 11:07 PM   #2
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They're 17W max plate dissipation. I've never found a datasheet; the only thing is a brief line entry in the RCA book.
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Old 25th March 2010, 01:27 AM   #3
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Do you think they're worth 5 NOS for $5? 17 watt dissipation is not a whole heck of alot.
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Old 25th March 2010, 01:43 AM   #4
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The one interesting thing is how much heater current it draws, 9.6 watts. A KT88 draws 10 watts and is rated for 42 watts Pd. I'm sure George could do a few "tests"
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Old 25th March 2010, 02:58 AM   #5
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RCA doesn't say much about this tube. The odd note is that it has a magnoval base. The magnoval was more comon in Europe and Japan than it was here. The magnoval is tha same as the 9 pin novar (compactron) base except the pins are fatter. You can stuff them into a novar socket, but once you do this an ordinary novar tube will no longer work. Google turned up pictures of GE and Sylvania tubes but both say "Made in Japan" on them. They look a lot like a 6GB5 / 27GB5 in height and diameter and those are also 17 watt tubes.

Quote:
I'm sure George could do a few "tests"
If I had some (it is possible but I doubt it) and they had a 12 pin base I would stick them into the red board and crank them up. Other 17 watt tubes made around 50 WPC in that design without getting upset. I had the 6GV5's up to about 70 watts before any glow was noticed.

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Do you think they're worth 5 NOS for $5?
$1 each? I don't know, do you have (or are planning to build) anything to use them in? Do you have suitable source for the odd filament voltage? Sockets? I am guessing that they would work fine in a 40 to 50 WPC amp, but some experimenting and circuit tweaking will be needed. Do you have the skills and equipment for this? Are you up for a challenge?

When ESRC had 6GV5's (a 17 watt sweep tube) on sale for $1 I bought 20, but they plugged right into the red board and run on 6.3 volts. Sadly the red board design wiped out his entire stock in about 3 weeks. For $1 each, I didn't mind "testing" a few. Nothing blew up and they ran fine at 50 WPC.

The 21KQ6 and the 29KQ6 are on his dollar list currently, and I just returned from a hamfest where I bought 70 more "dollar tubes", but this wasn't one of them. There is a 35 watt monster tube on the list, but no one has succesfully used them in audio yet. I spent $10 for my chance to tame the beast. Sound or smoke will result, I don't know which yet. Pictures forthcomming!
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Old 25th March 2010, 04:02 AM   #6
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Don' need no pictures of the sound, but pictures of the smoke are deRigeur, of course.

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Old 25th March 2010, 09:36 AM   #7
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Quote:
There is a 35 watt monster tube on the list, but no one has succesfully used them in audio yet.
can you name that tube please? is that a 6HF5?
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Old 25th March 2010, 04:36 PM   #8
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Quote:
can you name that tube please?
The 35 watt tube is the 6JD5. It is a 35 watt beam TRIODE designed for pulse regulator service. It is a relative of the 6HV5. These are triodes with a Mu of 300 and they draw almost no current with 500 volts on the plate and zero volts on the grid. A2 operation is required and the plate resistance will be high so some type of feedback is a must. OH, it really likes to oscillate too.
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Old 25th March 2010, 04:57 PM   #9
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Sounds like a cousin of 6BK4.. Always thought they would be good for direct-drive electrostat service
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Old 25th March 2010, 05:03 PM   #10
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Yeah, those beam triodes would be okay for ESLs... Really high mu and transconductance, despite the poor perveance.

Not really good for much other than high voltage and pulse regulation!

Tim
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