Which legitimate RF amplifier tubes are going to be available 10 years from now?

[loosecannon]

If you want 1500 watts and 3000 pep skip the GI-7b unless you buy a truck load of them. The old Russian tubes are already old and will not be made again.

An 8877 will almost get you to 3kw without abusing it but you'll need at least 4kv on the plate. Best to have a pair of them if you want 3000 pep. These are nice clean tubes with a lot of gain. 100 watts into a pair of them gets me around 3200 out. They will do over 5kw with more drive but the point is to make them last. They only have 25 watts of grid dissipation so you have to treat them right. Tune up with a carrier equal to driven pep, keep the grid current below 50ma per tube and they will live a long life. To get an accurate grid current reading don't tune up by whistling or talking into the mic.

A 3cx3000a7 will make the power you want and then some. Very clean and rugged tube. It has less gain than the 8877s would so you will need more drive. I would shoot for 5 to 6 kv on the plate. Plate and filament iron is expensive unless you stumble across a good deal.

The 3-500z is a nice tube but you will need a pair for 1500 pep and again I would shoot for 4kv on the plate. Unless you're strictly a ssb guy use forced air cooling with chimneys.

The Russian GS35B is still cheap for the power it makes. You could squeeze 3kw out of one but they are not so linear and once the surplus is gone they will be gone forever. I converted my 35b amp to 8877s because I wasn't happy with the linearity and wanted more gain. Runs good with 4kv on the plate. I ran their heaters for 24 hours before turning on the HV. Most of them were good but a couple were duds. Expect this to happen.

what a great reply!
thanks for that 543.

the info you provided was exactly what i was looking for, and i knew already that whatever transformer i can dig up is going to help me determine my tube choice.

Im going to make this jump slowly as my system wouldn't handle that much power right now anyway.
my goal right now is to come across an old amateur tube amp in terrible shape that has a good transformer, and maybe a usable chassis.

right now, it looks like the 8877 is at the top of my list.
i honestly don't care if i only get 2000 watts PEP when im shooting for 3000, and will be happy with anything in that range.

it will definitely be used in AM and SSB.
LC

 

[543_Dallas]

what a great reply!
thanks for that 543.

the info you provided was exactly what i was looking for, and i knew already that whatever transformer i can dig up is going to help me determine my tube choice.

Im going to make this jump slowly as my system wouldn't handle that much power right now anyway.
my goal right now is to come across an old amateur tube amp in terrible shape that has a good transformer, and maybe a usable chassis.

right now, it looks like the 8877 is at the top of my list.
i honestly don't care if i only get 2000 watts PEP when im shooting for 3000, and will be happy with anything in that range.

it will definitely be used in AM and SSB.
LC

On the transformer try to find something 2800-2900 vac and 1 amp. CCS would be nice. With a cap input filter that will put you near 4kv at idle.

Avoid old iron that seems like a bargain unless you want to find a choke and run a choke input filter. Most old transformers have high resistance windings and will crap out if used with a cap input filter.

Ameritron sells plate transformers for the al-82, 1200 and 1500 that will do what you want.

 

[Frank_va3]

look back 15 years to get the answer. Probably Chines and Russian tubes will run. They are good and better then the "originals". You don't get anything in Monrovia any more?
This website is full of advertisements and similar crap. It is a piece of shit.

 

[Shadetree Mechanic]

look back 15 years to get the answer. Probably Chines and Russian tubes will run. They are good and better then the "originals". You don't get anything in Monrovia any more?
This website is full of advertisements and similar crap. It is a piece of shit.

Welcome Frank!

 

[Tokin]

The viable tubes in 10 years will be the tubes you collect and maintain properly in and out of your amp. Some homework on how individual tubes store and how often to maintain stored tubes may also help you decide. Some of these tubes dont store for more than several months and need to be rotated thru an amp or they get gassy and can never be brought back. I know those are some points I would consider.
Everything popular today is being stolen and copied by China and poorly at best so I dont know what the tube supply be like in 10 more years. Probably a shit load of duds and fakes. You would do best to rely upon your own tested supply.
I dont claim to know much but I do know if im going to build a big amp I want it to put out twice the watts ill ever need so I can run it at an idle. No strain, no pain, never buy an amp again...
Thats my 2¢...

 

[Tokin]

look back 15 years to get the answer. Probably Chines and Russian tubes will run. They are good and better then the "originals". You don't get anything in Monrovia any more?
This website is full of advertisements and similar crap. It is a piece of shit.

Well you know, nothing is truly free. Instead of relying solely upon member donations to keep the site going there are a few ads to keep all this wonderful stuff at your fingertips.
There are other radio forums you can join, one that I know is ad free but its not near as active or friendly as this one. Most folks dont last there a few hours or even get past Introductions lol.
We're all a bunch of grumpy old farts around here and your grumpy ass is welcome to join us too, just scroll past the ads...

 

[Shockwave]

I've found the reliability of the GS and GI Russian surplus tubes to be horrendous. Experiencing a near 50% failure rate right from the start, even with burn in done first. Some have lost enough vacuum that the filament appears as a near short and won't even light to try a burn in. If you get one to work, staying well below rated plate voltage and about half of rated dissipation has kept one of my GS-35B running well for over 7 years. The weak vacuum just loves to create internal arcs between the grid and cathode.

The 8877 is a high performance medium power tube that is very over priced for the amount of dissipation available. Two of them still fall 1000 watts short of one 3CX3000A7, are far more expensive and cannot handle nearly as much abuse. If you build an 8877 amp, use filament chokes to hold the RF voltage equal between it and the cathode. Also consider adding grid over current protection to keep that fragile 25 watt grid intact during any mistakes. The Ameritron grid protection board can be added in to do this job easily.

 

[Staybolt]

Probably European, made in the communist block.

The 1980s called and want that comment back...

 

[Captain Kilowatt]

This website is full of advertisements and similar crap. It is a piece of shit.

That's what Adblocker Plus is for. I don't get any ads or pop ups here and next to nothing on other sites.