<VV> Re: Was Pertronix, Now Space Charged Tubes
JVHRoberts at aol.com
JVHRoberts at aol.com
Sat Oct 29 13:33:37 EDT 2005
Yes, the first two digits are heater voltage ONLY.
And there ARE tubes that can produce enough power in the output stage, but
NOT without a transformer!
As far as wattage goes, Ohm's law to some extent is at work here. If you
only have a few mA, you'll need LOTS of voltage to deliver the wattage. Besides,
tubes LOVE voltage. That's where they work the best.
It would be interesting to take a modern DVM through a tube Corvair radio
chassis and measure plate and grid voltages, since that's where the voltage
really is. I do recall seeing a '61 radio, and it had a tiny little vibrator,
looked like a capacitor.... Needed a stethoscope to hear the whine...
In a message dated 10/29/2005 12:34:34 P.M. Eastern Standard Time,
corvairduval at cox.net writes:
_JVHRoberts at aol.com_ (mailto:JVHRoberts at aol.com) wrote:
Keep in mind those first two digits refers ONLY to the filament heater
voltage. ALL stock tube radios for cars still had vibrators, and still needed MUCH
higher than 12 volts to the plates and cathodes to work properly.
The reason some used a transistor output was cost. It eliminated the need
for a relatively expensive output transformer, since tubes are high impedance
and transistors handily drive low impedance loads with significant power from
So, inside of that 'space age' radio, are still some pretty good voltages,
usually over 100 volts.
In a word, NO. Check the RCA Receiving Tube Manual and you will see the
following tubes were made with plate voltages of 12.6 volts. Cathodes in car
radios run near 0.0 volts. :
12AC6, 12AD6, 12AE6, 12AE7, 12AF6, 12AJ6, 12AL8, 12BL6, 12CN5, 12CX6, 12DE8,
12DL8, 12DS7, 12DU7, 12DY8, 12DZ6, 12EA8, 12EC8, 12EG6, 12EK6, 12EL6, 12EM6,
12F8, 12FK6, 12FM6, 12FR8, 12FX8, 12GA6, 12J8, 12U7.
None of these could produce power for audio output stage. Most run 1 or 2 mA
plate current. One was rated at 35 mA, but that is less than a 1/2 watt. You
will not see a vibrator in a Delco Corvair radio, but you will see tubes in
1960, 1961, and 1962. No hidden batteries, no multivibrator circuits to feed
step up transformers. No "high" voltage. The other car lines were also using
Space Charged tubes in the early 60's, like Ford/ Philco.
Tony, feel free to step in here.
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