View Full Version : Jumper for the Philco Predicta 21FDP4

03-22-2017, 10:59 AM
Okay this is the 2nd Predicta I have worked on with the 21FDP4 picture tube. Philco says the 8 ohm section of WR-3 must be shorted out to correct for the higher voltage required for the 21FDP4. This one does not have the jumper.
Whats are the effects if its not jumped out?

03-22-2017, 12:15 PM
There will be slightly more resistance in the filament string. If you have 117 AC line voltage, the filaments will run slightly cooler. If you have 121 AC line voltage, the tubes will have the same current as it was designed for..

Keep in mind we're only talking about 4 volts difference between the two CRTs. Much better to run the tubes a little lean