[AMRadio] Re: WRL Globe King 500C rebuild


W5OMR/Geoff w5omr at satx.rr.com
Fri Jul 7 00:37:39 EDT 2006


DLe9480907 at aol.com wrote:

>Hello to all . well have gotten around to trying to restore my king that  was 
>salvaged from a basement flood. the PS and Modulator are gone but the RF  
>Deck is rehabbed and working great on caw with an out board globe vfo or xtal.  
>The question now is will my new 2000vdc @600ma power supply be ok to power the  
>modulator also? and was wondering about the modulator. I have a Stancor A3898 
> 300 watt vari match mod xformer and was wondering about Tubes I have a good  
>supply of 813 (Triode connected) or 572b. what do youall think 
>
How much current is the GK500C drawing in the final, on CW?

If I understand the nomenclature correctly, the '500' would/should be 
around 500w DC input to the final.  With 2000v, that would put the 
current around 250mA.

I'd say you'll have plenty of current handling capacity at 600mA to 
handle the modulator.

I'm not that familiar with the "C" version... what are the modulators, 
811's?

I found this old 'ad' on somewhere out there on the 'net...

-----
Globe King 500C:  transmitter; Ad:  JAN 58 QST; price $795.00
wired; 540 watts AM, 540 watts CW, 540 watts SSB (with external
exciter); 160 thru 10 meters; bandswitching.  RF Section: 6AG7
crystal oscillator, 6146 buffer, 4-400A final, 12AU7 keyer, 6X5
and 5Y3 low voltage rectifiers.  Modulator:  6SJ7 speech
amplifier, 6AL5 compression rectifier, 6C5 amplifier, 6L6G
driver, push-pull 811A modulators, 5Y3 low voltage rectifier,
pair 816 high voltage rectifiers; Power Supply:  5U4G low
voltage rectifier, pair 866A high voltage rectifiers, 0A2
voltage regulator, 6AU6 VFO, 6CB6 VFO buffer; shipping weight
300 lbs.
-----

So, it's got a pair of 811A's.  I read also, somewhere, that the 
modulator deck had it's own power supply, that utilized a pair of 816 
mercury vapor rectifiers.

Unless you've got a seperate Bias supply for the 811A's at 2kVDC, I'd 
say it's probably a bit much B+ to run on 811's.  1500v in Class B is 
about good, for zero bias.

Yes, you'll have enough power supply with the 2kV @ 600mA, and the 811's 
will take the B+, as long as you put some bias voltage on the cathodes.  
An adjustable, well regulated bias supply between the 811A filament 
transformer center tap and ground would be a good place for that.

-- 
Driving your AM Rig without a scope, 
is like driving your car at night, without headlights. (K4KYV)

--
73 = Best Regards,
-Geoff/W5OMR





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