[AMRadio] Seeking tubes


Donald Chester k4kyv at hotmail.com
Fri Jul 8 02:07:39 EDT 2005


>Is the 849 about 10-12" high with the same type of pins? Looks about
>the same but no 'necks'? If so, I have a well used one still in the
>wooden crate and another with a case of the rattles (filament ist
>kapoot, methinks). Might consider trading one for a 204....

The 849 is similar, but bigger than the 204A.  It's the predecessor to the 
833A.  The RCA book says the 849, 204-A and 851 should all be mounted upside 
down so that the filament is up and the plate down.

I have run into a couple of hams on the air running 204A's.

The old pre-WW2 kilowatt RCA broadcast transmitter ran four 204A's in 
pushpull parallel, with a pair of 849 modulators.  Later, they changed to a 
pair of 833A's modulated by another pair - and even sold a modification kit 
to convert the older transmitter to 833A's.

Those older tubes were always expensive.  Back in the mid 30's, a 204A sold 
for about $85 - the equivalent to hundreds of dollars in today's money.  The 
newer 833(A) sold for a fraction of that.  That's why BC stations were 
interested in retrofitting their transmitters.

In the mid 70's I ran into about a dozen Amperex 849A's piled in a cubby at 
Young Engineering in Salem MA.  I couldn't get the guy to reduce his price; 
he wanted about $20 each for them, as is.  No way to test them, but they 
looked good.  I turned him down, and later, they apparently all got broken 
as they shuffled stuff around in the old warehouse.

I still kick myself for not taking a chance on those tubes.

Don K4KYV





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