[Boatanchors] National Rx.

[Carl]

----- Original Message ----- 
From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
To: "Al Klase" <al at ar88.net>; <boatanchors at mailman.qth.net>
Sent: Wednesday, June 29, 2011 7:19 PM
Subject: Re: [Boatanchors] National Rx.


>
> ----- Original Message ----- 
> From: "Al Klase" <al at ar88.net>
> To: <boatanchors at mailman.qth.net>
> Sent: Wednesday, June 29, 2011 3:22 PM
> Subject: Re: [Boatanchors] National Rx.
>
>
>> Larry,
>>
>> That's clearly an National HRO (Senior).  Note the sockets
>> for "big-pin"
>> tubes and the presence of the crystal filter on the right
>> side.  The
>> real cognoscenti could tell you more from the style of the
>> IF cans, etc.
>>
>> Al
>
>    I replied to the original sender and meant to copy the
> list. National changed from glass to metal tubes around 1936
> or 37. The advertising in the 1936 ARRL handbook shows glass
> tubes but remember that the handbook is set up the year
> before. I would have to look through a bunch of old QSTs to
> find the date of the change to metal tubes. I also don't
> know the date of the change of the IF transformers from air
> to ferrite core. National made a lot of changes, some of
> them small, over the production life of the "original" HRO
> from the first to the 5Ta1. All shared essentially the same
> circuit although there were some changes and National
> offered to modify existing receivers at the factory.
>    Its hard to tell just how much of this receiver is
> missing, its possible it could be restored but it would
> require replacing the meter, finding plug in coils, etc. I
> agree with Gary Pewitt that it looks like a restoral job
> that got inerrupted. Perhaps the seller has the missing
> parts sitting around somewhere (wishful thinking but you
> never know).
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com


National did not change to metal tubes until the middle of WW2.
They did change from 2.5V to 6.3V large pin tubes for AC operated sets 
around 36-37 when Millen was satisfied the hum problem from RCA was fixed.

Carl
KM1H