[Milsurplus] ARC-5 Receiver and other tube questions

[WA5CAB at cs.com]

6V6 and 6L6 were the first produced, followed by the G and then the GT for 
less critical applications.  

AFAIK, 6K6 or 6K6G were never produced.  Only 6K6GT.  For use where cost 
was the primary concern, as in BC-348-JNQ.  

In a message dated 2/17/2010 9:25:35 PM Central Standard Time, 
olegerityincj at austin.rr.com writes: 
> Ray -
> 
> I have a 6V6 in metal Its for sale for a price ;-}
> Hutch
> 
> On 2/17/2010 11:37 AM, Ray Fantini wrote:
> >I always thought the metal case tubes were newer and better design then 
> the glass tubes, the metal blocks inter electrode coupling, with a metal 
> tube you don't need a separate tube shield. The old primitive BC-348 receivers 
> used glass and shields where the newer series like the BC-348 Q used 
> modern metal tubes not requiring exposed grid caps and tube shields. The ARC-5 
> stuff never evolved into anything requiring a redesign like the BC-348 did , 
> the only thing I can think of is the late forties ARC radio equipment and 
> think that all used metal tubes with the exception of the seven pin stuff.
> >Question, why did some tubes stay in glass envelopes like the 5Y3 and the 
> 6V6 for so long? Was glass a better heat transferring medium for hotter 
> tubes? Cooler tubes like 6SK7 are hard to find in glass after the early 
> forties but 6V6 stayed in production in glass almost forever. I have never seen 
> a metal 6V6, where 6L6 was first a big glass tube then a smaller metal one, 
> are all 6V6 glass only? What about the 6K6?
> 

Robert & Susan Downs - Houston
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