motorola vt71 ts4j 3rd if issue- it wont light

[kramden66]

So if pin 3 & 4 are shorter that is the problem? If you pull the tube everything stays lit so it is making the series still work so must be something odd. Its not a wafer socket but one of those light brown or tan plastic type sockets.

[timmy]

Originally Posted by kramden66

So if pin 3 & 4 are shorter that is the problem? If you pull the tube everything stays lit so it is making the series still work so must be something odd. Its not a wafer socket but one of those light brown or tan plastic type sockets.

Do you have a schematic for it?

[bandersen]

Originally Posted by kramden66

So if pin 3 & 4 are shorter that is the problem? If you pull the tube everything stays lit so it is making the series still work so must be something odd. Its not a wafer socket but one of those light brown or tan plastic type sockets.

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.

[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.

[dieseljeep]

Originally Posted by dieseljeep

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.

I made a mistake on the disc caps. 250pf.
There has to be a fault on tube socket between pins 3&4. Maybe a solder splash or????.

[Kevin Kuehn]

Sorry, I completely spaced out that it's a series heater string. But that's a weird thing you have going on there.