Philco 49-1240 horizontal (?) problem

[Phil Nelson]

Originally Posted by miniman82

run the tube with the chassis and note the voltages on all the elements (K, G1, G2, ect).

I tested the element voltages with the old 12LP4 CRT in the cabinet and with my test 5AXP4 CRT on the workbench.

The voltages are basically the same on either CRT for G1 (pin 2) and G2 (pin 10).

On the test CRT, the cathode (pin 11) voltage varies from ~25vdc - ~140vdc depending on the Brightness control setting, with about 40vdc giving a normal picture.

On the old CRT, the cathode voltage is zero under all settings.

Rapping the tube neck doesn't change anything.

The Sencore CR70 manual says that some tubes with open cathode connections can be welded with the "Remove G1 Short" function. Basically, you try this function while rapping on the tube and watching for a bright flash.

Phil Nelson