[Milsurplus] Re: BC375 805s for 211 modulators

[Kenneth G. Gordon]

Marty wrote:

> Was: More on BC375 Tube Subbing* 
> 
> 211 a lo amp-factor (10) critter per '57 hdbk. 

Yup. My 1938 edition of the RCA Transmitting Tube Manual says the 
same, but has more data than the hdbk.

> 
> 805 is same.  But has plate cap which is no impediment in modulators.  
> Just paint caps black & run poly wire to 'em behind the tubes.   EXACT
> electrical swap.

Yup.

> 
> 838 amp factor not given there but fine grid-pitch makes them
> look like hi-mu 811s or 572Bs.  And someone here proposed they might
> be sub'd for 211s running at zero rather than neg. bias (as pot 1113
> sets in BC-191).  So conditionally a good modulator 211 exchanger.

Yes. Excellent modulator tube.

> 
> There were a blue mil 805s in surplus & outside of scarce T350XM, don't
> know where they went.  838s were finals in giant shipboard 'Battle Announcer'
> Stromberg built for Navy & fewer in circulation than 805s.

I have a quad of them here, which came out of an old broadcast 
transmitter. Apparently the broadcast industry used them like peanuts 
for a number of years.

> 
> Anyway - Tempe place advertises these prices
> 
>     211/VT4C   $195
>     805        $105
>     838         $61

At least 1/3 too high, IMHO.

> 
> & DaveS sez Chinese 211 clones $30.  If ya gotta buy 'em, nolo contendere.

I bought a pair of these to use in my homebrew 1929 replica push-pull 
211s TPTG rig. They operate identically to the pair of VT-4C/211s I 
bought off Ebay, and look identical too. They are pretty well made. 
Even the audio-phools use them on occasion.

There was a fellow who wrote an article for ER magazine a few years 
ago who uses the Chink tubes in his BC-375 and says that there is no 
difference in the way it operates, or in their reliability either. He swears 
by them in that service.

If I had a BC-375, I wouldn't hesitate to use them in it.

> 
> Note all are 10V 3.25A filaments.   Much needed with all series
> resistors to get 'em going off 14 or 28VDC in a '191 or '375.

Yup. I have a bunch of 10V 10 A filament transformers out of junked 
Phillips research x-ray machines I use for mine.

Ken W7EKB