[Boatanchors] Pullen Mixer (nee: Anyone Noticed)

[Carl]

The 2nd oscillator received enough drift complaints that changing it to 
crystal control was a no charge mod for every 300 that came into the Service 
Dept at National. A kit was also available at low cost. Theses days its 
mostly an AM radio but in the 60's it was SSB and CW.

Carl


>
> Carl wrote:
>
> "The thought has crossed my mind as the 6BA7 is as bad in the NC-300 as in
> the 75A4 and I changed both of those to 7360's in 65 and still use that
> radio.
>
> First step is to go thru it, recap and resistors plus xtal control the 2nd
> mixer/osc. Get it back to spec and then play.
>
> Ive never owned a 300, worked on many including recently, and did have a 
> 303 for a few years in the 90's."
>
>
> I've wondered why so many manufacturers of communication equipment stayed 
> with pentagrid mixers rather than use a triode mixer such as the Pullen. 
> Orthodoxy? Perhaps most of the designers had previous experience in the 
> consumer electronics market where, for the AM broadcast band at least, 
> pentagrid converters were the norm?
>
> I have an NC-300 and have noted that it is a less than stellar performer 
> on 10, even after replacing out-of-spec parts and after careful alignment.
> But, yes, an in-spec unit has to be the starting point for modifications.
>
> Is the stock LC oscillator for the second mixer in the NC-300 a source of 
> trouble?  I have not noted excessive drift in mine.
>
> Drew
>
>
>
>
>
>
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