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Re: [TCML] First VTTC - Some help needed choosing tubes


There are (or were) outfits that would rebuild big industrial power tubes for a price.  They could dismantle and reassemble them, but there were special skills and tools required.  It's probably becoming a lost art.

Pumping down a tube will require a bake-out oven, and roughing and diffusion pumps.  IIRC, most vacuum tubes require a very clean vacuum around 10^-6 Torr, which is not easy to achieve, and then you have to seal off the exhaust port in a way that will not leak.

I am not aware of any gas filled tubes being used in the standard VTTC model.  Gas tubes are generally thyratrons or rectifiers, not amplifiers.

Starting from scratch will be even more daunting.  Effective envelopes, filaments, getters, and plate structures often involve some exotic alloys and compounds,

Given the relative abundance of suitable vacuum tubes out there on the 'bay, you are definitely better off buying one ready made than trying to repair or build one from scratch, unless you want to invest lots of time and $$$ in tube production.

There are many ceramic power tubes like the 3CX.... or 4CX.... series out there, in any kind of wattage you could hope to drive. Just finding (and powering) a filament transformer for some of the big tubes is an adventure in itself.

You can make a very nice VTTC with 1-4 833A tubes, and the 833C variants with the graphite anodes can handle even more power.


On 12/27/2018 11:06 AM, Tedd Dillard wrote:
Has anyone ever heard about either repairing a damaged tube or even
building one from scratch?
Seems like it may not be that difficult given that for coil use you have
specific capabilities needed compared to the broad use that these tubes
were intended for. How good of a vacuum is needed? Are they, can they be
gas filled?

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