RCA 5762/7C24 Tubes

From:  Robert W. Stephens [SMTP:rwstephens-at-headwaters-dot-com]
Sent:  Monday, June 01, 1998 5:57 AM
To:  Tesla List
Subject:  Re: RCA 5762/7C24 Tubes

> ----------
> From:  Pete [SMTP:casius-at-cyberserv.co.za]
> Sent:  Monday, June 01, 1998 11:55 AM
> To:  tesla-at-pupman-dot-com
> Subject:  RCA 5762/7C24 Tubes
> Hi to all,
> Has anyone out there had any experience with the RCA 5762 / 7C24
> transmitting tube. I believe it to be a triode capable of 5kW. By the
> size of the tube I guess that the household wiring would not be able to
> support the power supply.
> Regards
> Pete

Pete, All,

The RCA 5762 triode is a terrific tube for a largish vac toob TC if 
you can get your hands on one or more!

Fil.  12.6 V -at- 29 A
Amplification Factor 29
Plate Volts Max 6200
Plate Dissipation Max 3000 Watts

Used as a self rectifying oscillator (as in Tesla coil with mains AC 
on the plate supply, or an industrial heating oscillator) the RCA data sheet
has the following advice:

Maximum Ratings
AC Plate Volts (RMS)... 7,000 max. volts
DC Grid Voltage...-300 max.volts
DC Plate Current...0.625 max. amps
DC Grid Current...0.135 max. amps
Plate Input...4,900 max. watts

Typical Operation
AC Plate Voltage (RMS)...6,600 volts
DC Grid Voltage...-127 volts
DC Plate Current...0.625 amps
DC Grid Current...0.105 amps
Driving Power (approx.)...60 watts
Power Output (approx.)...3,350 watts

The thoriated tungsten filament has a center tap which should not be used 
for heater current but is offered as an extra place to add a bypass 
cap to ground when the tube (good for up to ~220 MHz) is used at 
higher frequencies.

I have canibalized two RCA BTA-10K AM broadcast transmitters which 
originally came outfitted with 5 of these RCA 5762 tubes each.  A pair in 
push-pull as the modulator and three tubes paralleled for the RF final.  My 
transmitters came with an English Electric Valve higher performance 
direct replacement of this old RCA tube which are rated at a 
considerably higher 5 kW of plate dissipation.  I am using three of 
these newer EEV BR1160 triodes in parallel in my Coronatron (hi-power 
vac toob TC).

The RCA or EEV tubes have an external copper finned jacket anode about 5 
inches in diameter which sit (fil. end up) in a special spring 
fingered socket cup which is pressurized by a high CFM blower.  A 
second cooling air nozzle must be directed sideways and downwards 
directed at the filament terminals coming out of the top (fil. end) 
of the tube to keep the seals cool.  To insure long service life 
ALWAYS allow 5 minutes of filament warmup time before applying plate 
current!  Once they are up to temperature the filaments should be 
left on if the unit is to stand idle with plate supply off for up to 
several hours and then be re-used.  These tubes require serious 
airflow at max ratings.  I'd recommend about 1/3rd to 1/2 horsepower of 
turbine blower per tube.

Normal wimpy house wiring (except 230 volt stove or dryer circuits) won't 
fully excercise this tube but if you wire your project directly to the main 
panel you should be able to have some *serious* fun! : )

Good luck.

Robert W. Stephens
Lindsay Scientific Co.
RR1 Shelburne, ON Canada L0N-1S5
Tel: 1-519-925-1771   Fax: 
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