[NJARC] Re. inconsistent tube types

[Al Klase]

Comments below:

Paul Rutkowski wrote:
> Visit our web site - See http://www.njarc.org
> _______________________________________________
> Dave, Al,
> Thanks for your quick responses!
> Looking at the schematic from nostalgiaair.org,
> I see now that there are 2 problems:
>
> 1.
> For the Audio Output tube, a 35L6GT is being used instead of a 50L6GT.
> Am I correct in assuming that this is a dangerous substitution,
> and that I should replace it pronto with the correct 50L6GT?
>   
I don't know if dangerous is exactly the word, but all the tubes are 
going to see increased filament current, which will shorten their lives 
somewhat. Change out the tube when you get a chance.
> 2.
> The radio’s back label, which clearly states Air King model A-511,
> shows the rectifier as a 35W4, even though the schematic
> (and physical reality) shows 35Z5.
> As you said, these tubes have different footprints,
> so I can’t explain that radio label.
> (Could this be a valuable misprint, worth millions of dollars?)
>   
I can imagine a situation where 35Z5's were in short supply, or they got 
some 35W4's cheap, and built a run of sets with the alternate tube. 
Perhaps they had more backs than 35W4's. These were cheap radios, and 
the goal was to ship units.
> One other question:
> This radio also has metal 12SA7 and 12SK7 tubes where 
> the schematic specifies 12SA7-GT and 12SK7-GT tubes.
> Are GT and non-GT tubes interchangeable?
>   
At least in simple radios they usually are interchangeable.
> Are there any reasons to use one versus another?
> (besides the pleasure of seeing the glow of the GT's?)
>
>   
The metal tubes are inherently shielded. The shield is connected to pin 
1 in most cases. A lot of radios can get away without shielding. If I 
had trouble with unwanted oscillations ("birdies") or couldn't peak the 
alignment settings, then I'd revert to the tube type in the original 
schematic. Otherwise, go with what's in the set. The glow IS a plus. :-)

Al

-- 
Al Klase - N3FRQ
Flemington, NJ
http://www.skywaves.ar88.net/