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.
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.
$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!
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.
$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!
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.
You guys are thinking about the wrong tubes. The 6BK4 and its relatives were the first generation of HV regulators used in color TV sets. It operated on the secondary side of the flyback and had a typical plate voltage of 25 to 28 KV DC and a maximum plate current of about 1 mA. Running anything that puts 25KV in a vacuum will generate X-rays. For those of us that are old enough to remember, old color TV sets did generate unsafe levels of X-rays, which caused multiple itterations of HV regulator shields, and finally a new design. Except for maybe ESL's they are generally useless.
The 6HV5, 6JD5 and about a dozen others are from the second generation of HV regulators used in color TV's. They operate on the primary side of the flyback transformer and thus deal with pulses rather than HV DC. The theory is that if you limit the peak of the primary pulse you will limit the HV. These tubes operate with a DC voltage on the plate in the 500 to 1KV range and are normally non conducting. They will turn on for a brief instant during the horizontal blanking interval, seeing a peak plate voltage in the 2 to 3 KV range. There is therefore no real linearity requirement.
Physically they look like a big sweep tube with no screen grid. The 6BK4 looks like an X-ray tube!
I did get some sound out of a 6HV5 a couple of years ago. It is not possible to design a simpler amplifier, since it used a power supply, the tube, the OPT, and NOTHING ELSE! I connected my Sony Discman (headphone output) between the cathode and grid, and connected an OPT and a power supply in series between the cathode and plate. I had to dial the power supply up to max (550V) to get any current. The power output was a watt or two and it sounded pretty nasty, but it worked.
I an visualizing ways to stuff these into the red board. Its safe to assume, somethings going to go boom.........
Last edited:
I got a small batch of 6JD5's too out of curiosity and they're cheap. I'll have to figure out how to make an extra safe chassis first. Most of what I've seen so far uses voltages around the 1kv range. Hermetically sealed amplifier? 
Before I ever get around to those I've been looking to do some experiments on some 22JF6's. I've got an old bogen PA amp with novar sockets that may get abused.
Before I ever get around to those I've been looking to do some experiments on some 22JF6's. I've got an old bogen PA amp with novar sockets that may get abused.
I have 1 and 2 KV Kepco power supplies, but they are stored safely a few miles away in my warehouse in case I get the urge to do something stupid. There is currently a power supply on my bench that puts out 0 to 650 volts at up to 1.7 amps. For now I am considering that to be the limit on amplifier sanity. That is where I intend to experiment with these tubes.
High voltage pulse tubes. Class-D output stage anyone? Way over my head. http://www.diyaudio.com/forums/class-d/69538-tubes-class-d-2.html
Tube amplifiers for high-end audio by The David Berning Company
Tube amplifiers for high-end audio by The David Berning Company
I just bought 10 29KQ6's for $1.00 each for an ESL amp project. All are Westinghouse tubes in boxes and look new. The plate caps I got with them don't fit! I measured the tube and It is .250 inch. I think I got what I ordered but now I'm confused. Looking around the web for plate caps I see "small" "medium" "large" "6mm" and "9mm". And looking at tube data sheets I see "minature" "small" and "large". So what fits a 29KQ6?
Jim
Jim
I bought some of the ceramic plate caps currently available, also small size, and had to pull out the metal and slightly reform it. They were much to tight, so tight I would not force them on, but I'm pretty sure I have the correct size. I assume just loose manufacturing quality. They will work but I am going to keep my eye open for a better style.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.