Below are some e-mails I have collected over the past few months that talk about the VT52 tube.

>> has the same size as a 45 ST bulb. I have 6 VT52s here, and can see three
>> different plate sizes. Considering that heater voltages also differ between
>> the different brands, it seems that noone agreed on a standard for these
>> tubes :( I get conflicting specs for heater voltages from specs on the
>> same tubes...

> I agree completely. Someone told me once that the 7 volt VT52s were genuine
> while the 6.3 volt types (e.g., Sylvania) were actually 6A3 monoplates that
> were relabled during the war! Interesting and, somehow, it has the ring
> of truth about it,

>> I recently bought some VT52s. After unpacking I noticed that I had 3
>> differing plates amongst these tubes. Also the heater of one tube was made
>> up of a W section while the other were VVV fillaments. Considering the fact
>> that heater voltages differ between the different brands, is it possible
>> that these are single section 6A3's instead of VT52s? Looking at the specs
>> of a VT52, they come close to matching those of a 2A3... Does anyone have
>> any suggestions...???

> I'm not convinced that the filament voltages differ with different brands
> of VT-52s. The only source for this, that I know of, is "75 years of WE
> tubes" or whatever it is by Bernard Mangers. His statement that it is a
> seven volt tube is a little vague. This has been repeated over and over
> that WE VT-52's are seven volt while the other brands are 6.3. I think that
> it may be a mistake about the WE version. This tube was only used in
> military gear for a very short period of time. It's hard to believe that a
> spec as important as fil voltage was changed in a few pieces of equipment.

> Oh it's possible of course but I don't think the evidence is very strong
> for the WE being a 7 volt tube. Has anyone ever actually seen a data sheet
> for _any_ brand of this tube? I run my WE at 6.3 and will do so until more
> reliable information is available. From what I can gather from a article in
> MJ (not much) the author thought that WE VT-52's are 6.3 volt tubes.

>> Oh it's possible of course but I don't think the evidence is very strong
>> for the WE being a 7 volt tube. Has anyone ever actually seen a data sheet
>> for _any_ brand of this tube? I run my WE at 6.3 and will do so until more
>> reliable information is available. From what I can gather from a article in
>> MJ (not much) the author thought that WE VT-52's are 6.3 volt tubes.

> In a book about tube amplifiers by Naoki Watanabe published in 1988 by MJ.
> The table page 346 gives:
> VT 52: Ef (V) If (A)
> Western Electric 7 1.18
> Sylvania 6.3 1
> Hytron 6.3 1

> How about this-- I have a VT-52 (Hytron, I believe) that has VT-52 on the
> base and 6A3 stencilled on the glass.

>>> I agree completely. Someone told me once that the 7 volt VT52s were
>>> genuine while the 6.3 volt types (e.g., Sylvania) were actually 6A3 monoplates
>>> that were relabled during the war! Interesting and, somehow, it has the ring
>>> of truth about it,

>> Sounds right, but if you look at the given gm for these two tubes you see
>> that the gm of a 6A3 is about 5500, while a VT52 should have about 2200...

> Are you sure that the 6A3 MONOPLATE doesn't measure more like a VT-52
> than a dual plate 6A3?

>> BTW, Do you know of a way to see what voltage the heaters should have. I
>> don't have a tester so I can't test for emmision etc... How do you know if
>> it should be a 6.3V or 7V heater???

> It's easy. Just run the tube at 7 volts. If it blows up, it should have been
> run at 6.3 8*) More seriously, buy or borrow a decent tester. It really is
> a useful tool. That being said, however...
> As far as I know only the Western Electric/National Union VT-52s have seven
> volt filaments. All the others require 6.3 volts. To confuse things even
> further, many Hytrons (but not all) were constructed more ruggedly than other
> VT-52s and could safely dissipate 18 watts. Lots of fun.

>> Hmm, any other data on this tube, perhaps even a complete datasheet of
>> sorts? If so I'd be very greatfull for a copy/scan...

> Sorry, no complete data sheet, but I give you the datas from the table about
> 6A3 and VT52:

> Ef If Ep Eg Ip Rp Gm mu RL Po max Plos
> (V) (A) (V) (V) (mA) (ohms) (ohms) (W) (W)
> 6A3 6.3 1 250 -45 60 800 5250 4.2 2500 3.5 15
> VT52 220 -43.5 29 1650 2300 3.8 3800 1 15
> 300 -60 40 1600 2370 3.8 3580 2.4 15
> WE 7.0 1.18
> SYLVANIA 6.3 1
> HYTRON 6.3 1

>>> And the editors of Stereo Sound list the following for the Sylvania VT-52:
>>> rp = 1.377K ohm
>>> mu = 3.8

>>Ah, the Rp was one of the things I didn't have yet... Thanks... Any other
>>data in here about this tube???

> Not data, but I can give you the recommended operating point:
> Ep - 300v
> Ip - 43.5ma
> Eg - (-60.9v) (and don't even bother trying -60.8!)
> Rload - 3.3Kohm
> Power out - 2.0w

> The 45SPL is also know as the 38142, 2C45, and VT-52. It's a transmitting
> triode 45, with a 7 volt 1.18 amp filament. It was made by National Union
> under contract from Western Electric for use in BC-230/430 aircraft radios
> and also distributed by Hytron. That's about all I know about it.
> The VT designation is just that it was a Military tube type. The numbers
> don't have a whole lot of intelligence to them and were probably used just
> to make it harder to figure out the design of any radios that fell into the
> "wrong" hands

> I've just read your collection of mail concerning the mysterious VT-52 and
> found it very interesting. Here is some info and speculation I would like to
> add. I own 3 Hytron and 2 WE VT-52's and a friend of mine has 5 Raytheons
> (which I am conspiring to obtain). The Raytheons are interesting because of
> the box-shaped plate -- characteristic of their "four-pillar construction".
> The equivalents given in the U.S. military publications of "2C45" and
> "38142"(Jan no.) provide some clues though not concrete proof regarding
> filament voltage. These numbers appear in the test data booklet for the TV-7
> and the roll chart of the TV-2, respectively. Both tube testers specify a
> filament voltage of 7.5v (!). However, when tested at this voltage the
> filament is unusually bright and the results are high, except for the
> Raytheons. Furthermore, the tube complement of the BC-( )-230 radio is three
> VT-52s and five VT-25s (a dream). Of course, we all know, the VT-25 has a
> 7.5v filament. In fact, as far as I can tell, the VT-52 was only used in Army
> equipment with the VT-25 so one may reasonably assume they shared the same
> filament transformer. Anyway, it is a superb audio tube and I intend to run
> mine at 6.3v with a plate load of 7000 ohms.