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Golddustpeak

Tue May 24 2016, 10:07PM

Registered Member #54266 Joined: Thu Jan 15 2015, 02:03PM
Location:
Posts: 4

Hi all,
I'm looking for some tube suggestions for a 1KW (or so) VTTC.
I currently do not have any desires other than a inexpensive triode that I can purchase several of in case I destroy one or two.
I have a source of 1kv or 2kv at about 600Ma.
My thoughts are on the order of 811, GI-7B, 572 (getting pricey), 810, 833.

TNX

nzoomed

Wed May 25 2016, 09:52PM

Registered Member #54503 Joined: Sun Feb 22 2015, 10:35PM
Location: New Zealand
Posts: 288

Try some 807 tubes, they handle quite alot higher voltages that what the datasheet claims.
even if you do blow them, they are such a plentiful and cheap tube it does not really matter.
You can have the plates glow red on those without any issues.

Other than that, you could try the eimac 35T which is a real good transmitter triode capable of high voltages.
All the tubes you mention should also be suitable, but you can run most power tubes in triode mode, you just connect the screen grid to the anode.

You could try some 807 and see how long they last just for interest.

How many tubes are you after?
Are you running them in pairs?

I have 3 spare Eimac 35T available, i think these would be the most reliable out of the lot mentioned here.

Golddustpeak

Fri May 27 2016, 02:22AM

Registered Member #54266 Joined: Thu Jan 15 2015, 02:03PM
Location:
Posts: 4

"How many tubes are you after?
Are you running them in pairs?"

I would like to approach a power level of 1 Kw so the number of tubes would be dependent on the plate voltage and dissipation.

nzoomed

Fri May 27 2016, 02:59AM

Registered Member #54503 Joined: Sun Feb 22 2015, 10:35PM
Location: New Zealand
Posts: 288

Golddustpeak wrote ...

"How many tubes are you after?
Are you running them in pairs?"

I would like to approach a power level of 1 Kw so the number of tubes would be dependent on the plate voltage and dissipation.

Dont know on price but GI-7B, but those would be your best bet.
A push pull pair would give you close to your 1KW.
807 tubes would give you around 60W max each, maybe more.

811 wont give you much more than 60W either and that is at its maximum ratings, for an expensive tube.

Golddustpeak

Fri May 27 2016, 12:21PM

Registered Member #54266 Joined: Thu Jan 15 2015, 02:03PM
Location:
Posts: 4

I'm tending to lean towards the GI-7B as I'm seeing them sell for $25.00 or less here in the USA.
The only problem that I have with them is that they do not have the visual appeal that a glass bottled tube has to me

nzoomed

Fri May 27 2016, 09:56PM

Registered Member #54503 Joined: Sun Feb 22 2015, 10:35PM
Location: New Zealand
Posts: 288

Golddustpeak wrote ...

I'm tending to lean towards the GI-7B as I'm seeing them sell for $25.00 or less here in the USA.
The only problem that I have with them is that they do not have the visual appeal that a glass bottled tube has to me

Yes i agree, especially considering that 807 tubes make a nice bright blue glow when lots of current is passing through them!

GrantX

Sun May 29 2016, 06:31AM

Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335

I have a GS-9B sitting on my desk now, which has identical dimensions to the GI-7B. Originally I was going to use it in a small HF VTTC, or a generic RF amp. It was very cheap, but I've noticed that the sockets are more expensive than the tubes!

My current plan is to improvise a socket using a bunch of hose clamps. I salvaged a bracket that was holding an electrolytic capacitor, which luckily is the perfect diameter to fit the grid connection and has several mounting points for attaching the tube to a chassis.

This site has some sockets for sale, including a very nice 5mm thick copper bracket for holding a pair of tubes, and a gigantic heatsink for running a GI-7B without a cooling fan. That site has certainly given me some ideas for my GS-9B... :)

Golddustpeak

Sun May 29 2016, 12:17PM

Registered Member #54266 Joined: Thu Jan 15 2015, 02:03PM
Location:
Posts: 4

Here is a link to a GI-7B site you may already have seen.
If not there are some self made socket photos at the bottom of the page.

GI-7B info

sparky99

Fri Jun 24 2016, 09:13PM

Registered Member #1159 Joined: Fri Dec 07 2007, 02:10AM
Location: Hudson Valley of NY State
Posts: 84

811's & 572B's are expensive. They are used in lots of lower power linear amplifiers, such as the COLLINS 30L1 & several Ameritron amps. 811's are not very robust.....I've seen lots of them with holes burned in the plates. I'd go with 833's.....and they look great with the filament powered up!

Bob
N2OAM

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