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Re: tubes
Hi Ed, all,
> Original Poster: "Ed Phillips" <evp-at-pacbell-dot-net>
snip
> There were an almost infinite number of UV203A and VT4-C triodes
> available surplus after WW2, and there are probably a lot still
>kicking around somewhere. Nominal 50 watt dissipation, filament
>3.25 amps at 10 volts. I suspect two or more in parallel would give
>quite respectable performance.
Uhm, I wouldn´t use a VT-4C or GL-211 (same tube, except that
the VT-4C has military specs and is maybe more robust) for pure
experimental work. The last time I saw one of these on the internet,
they (a company) wanted $550 for one in original packing, mint
condition and only 15 hours run time. I just happen to have one of
these in the same condition with zero hours runtime. Hehehe ;o).
However, if you can find them for cheap, they really should make
a great toob TC. I got mine back in high school for just that purpose
(for free). I had begun construction, but we moved over here around
that time, so I had to discontinue work on it. Somehow, I lost one of
the two VT-4C tubes I had ;,,,,,o( (sniff), so now I only have one
left and that ONE is never going to be lit up. It is (among other tubes)
just on display, next to my collection of old tube equipment. Now, I
wish I had taken one of those gigantic rectifiers which my dad had
used in his plasma lab (a picture of these tubes can be seen on my
website). To give you an idea of the size of these monster mercury
rectifier tubes: They are ~3.5 ft long and the lower glass tube is 10"
in diameter. The globe (containing the plate) is roughly 20" in
diameter. Did someone say huge tubes? I don´t remember the exact
weight, but they were pretty heavy (as one can imagine, esp. since
they were loaded with mercury). Would have been a cool addition to
my small collection............
More data on the VT-4C
(original GE data sheet from 9-20-39 ;o)):
Interplate capacitance (grid-plate): 14.5 µµF (µµF=pF)
Jumbo 4 large pin base
(all voltages are MAX values):
--------------------------------------
DC plate voltage: 1250V
Grid voltage: -400V
Plate current: 175 mA
Grid current: 50 mA
Plate dissipation: 100 Watts (Class C RF power amp)
Peak RF grid input voltage: 375V
Driving power: 7 Watts
Under 15 Mhz the above values may be exceed by 5%.
The resonance frequency of the grid-plate circuit is 100Mhz.
The filament is of thoriated tungsten type, so it is best to
use ac for heating, but it will need to be well watched, that
the voltage stays within 5% of the nominal 10V
BTW: If someone out there collects old German tube radios
and needs a schematic, I might be able to help out as I have
some 4000 pages of copied (puuh) schematics.
Coiler greets from Germany,
Reinhard