motorola vt71 ts4j 3rd if issue- it wont light

[dieseljeep]

Originally Posted by bandersen

Yes, pins 3 and 4 are the filament. They must be shorted otherwise the other tubes could not be lit up with that tube pulled out.

The schematic shows 5000pf heater bypass caps in the IF strip. Check for a shorted cap. Also, one of the tubes in the same string may have an H-K short.
The tubes are in a series-parallel arrangement.