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

[Richard Knoppow]

    I can't find any other place where a Type 77 is shown like this. I 
think its an error that was repeated in the schematics. The 77 was 
recommended by RCA for use as a plate detector, which is the application 
in the BC-221. I wonder if there are schematics from other sources.

On 12/16/2016 8:41 PM, J Mcvey via ARC5 wrote:
> If you look closely, the first and third grids are tied together
> INTERNALLY, so it's basically three gris. I guess they wanted to be more
> specific about the internals?
> This site has 4 pdfs for that tube, One shows it as 4 grids also, but
> describes it as "triple grid".
> .https://frank.pocnet.net/sheets/127/7/77.pdf
>
>
> On Friday, December 16, 2016 10:47 PM, Leslie Smith
> <vk2bcu at operamail.com> wrote:
>
>
> 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 <mailto: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/ <http://www.tubedata.org/>
>               or    http://www.duncanamps.com/
>
>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL