[ARC5] OT - the BC-221-D, tube types.

[WA5CAB at cs.com]

Les,

Yes, the 77, VT-77, 38077 has a small 6-pin base, and a grid cap.

It was used in the BC-221-A, -C and -D, the Navy RU-3 and later, and in 
three equipments I've never heard of.  I don't have any paper on those three 
but do have something on almost all of the RU's.  I don't have TM 11-300A, C 
or D and I don't have the 1942 edition of TM 11-300.  TM 11-310 only has the 
schematics for BC-221-AE and later.  I have all of the RCA Receiving Tube 
manuals from 1933 on.  I have several versions of the manual and the tube 
settings booklet on the I-177-(*).

In all of those locations, the only one where the 77's control grid is 
drawn on both sides of the screen grid is in the BC-221-A and BC-221-C & -D 
schematics and their stage by stage drawings in the 1944 edition of TM 11-300.  
In all of the other documents containing a basing diagram of the 77, it is 
drawn as a standard pentode.

So all that I can suggest is to ignore it and go on.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 12/16/2016 21:47:04 PM Central Standard Time, 
vk2bcu at operamail.com writes: 
> Hello All:
> 
> I'm looking at the circuit diagram for the BC-221-D heterodyne frequency
> meter.
> I see the tube used in the oscillator circuit has the part designation
> VT-77.
> In the drawing I see a device with four grids - I haven't unplugged the
> VT-77, but I suspect it uses the six pin UX-6 socket.
> 
> In the cross-reference list I see a VT-77 is equal to a type 77 pentode.
> In the RCA datasheet I see tube type 77 is  described as a "triple grid
> pentode".
> In my understanding - this is a standard early pentode - and I would
> guess not too much different from the more-modern (octal) 6K7 or 6SK7.
> 
> I believe the US military documents are often reliable; I cannot
> understand why the VT-77 is drawn with 4 grids.
> 
> Help!!
> 
> 
> 73 de Les Smith
>    vk2bcu at operamail.com
> 
> 
> References:  (1) Technical manual for the BC-221-x series:  TM-11-300.
> Circuit diagram for the BC-211-D is presented on pg 42 of that manual.
> The tube data for type VT-77 or 77 pentode is available from Frank
> Phillips tube data pages:
>      Link to:    http://www.tubedata.org/   
>                or     http://www.duncanamps.com/
> 
> 
> -- 
> http://www.fastmail.com - Choose from over 50 domains or use your own
> 
> 
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