Moment(s) of Truth
Working, restoring, rebuilding, checking, validating all seem to be enjoyable. Each step of the process is thought out and the expected result is a function of ones skills in performing each step. But turning on the power. Well. For some reason the adrenaline increases. The heart rate goes up. One stands back from the open enclosure to prevent personal injury should there be a flash over.
But nothing happened other than the metering lights illuminated. After 180 seconds the dial lights illuminated indicating that the prerequisite time to warm up the 4CX1000A cathode has elapsed and it is now OK to turn on the high voltage. Check the filament voltage and it is 6+ VAC (since no tube has been installed at this point). Check the bias voltage and it was adjusted to -80 VDC. All other readings of the multi meter are zero. So far so good.
Now. Turn on the high voltage. Again. Nothing happens except the Red HV lamp comes on! Check the HV reading and it indicates +3200 volts.
The heart rate starts to return to normal. I reach for a cold one. That Coke sure did go down smooth!
So the next step is to install a tube. The original 4CX1000A was installed. Turned on the power and then the HV. Set the filament voltage to the requisite 6 VAC. All meter readings read nominal. Key the amplifier. Still NO smoke or noises. Adjust the idle plate current to 200 mA. Plate voltage drops to 2800 VDC. All readings nominal except grid current. When the amplifier is keyed with no RF, there is a small amount of negative grid current. This 4CX1000A is destined for the scrap heap.
Installed my spare (looks new) 4CX1000A. Again all multi meter readings nominal and there is NO discernible grid current with this tube. On to the next step. Introduce some RF into the 30S-1 and lets see what kind of rebuild we mustered.
Well. Well. Well. Lookie see. 30 watts of drive and 700 watts output. Just like the original specification in the Collins 30S-1 operating manual. I guess we did alright with our rebuild. This one is for you Bob.
BUT. The story does not end here.
Next we replaced the 4CX1000A tube with a 4CX1500B tube. Result? 30 watts input and 950 watts output. Things just keep on getting better.
BUT. The story does not end here either.
Next we installed the screen boost transformer that came with my bushel basket project. This boosts the screen voltage from 200 VDC to 325 VDC. Result? 1500 watts output!
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