19AP4 issue help
 

Hello all!

I recently picked up a DuMont 19ap4 that came out of an ra-109... The tube tested ok but had a loose base. So I decided to fix the base but in the middle of trying to slip the extended wire leads through the pins one of the heater pins broke and I am afraid the tube might have gone to air because I cant get a filament glow when I soldered the wire back on the lead near where the pin sticks out of the glass. Is the tube possibly dead?

It's possible... Are you sure it's the right pins.....?

Best thing is put a small bead of silicon clear around the base where it contacts the
glass in the future.... Disturb as little as possible on something that delicate....
Remember you don't know if those wires are corroded before removing, so
if not absolutely necessary, leave it alone....

.

Absolutely positive it was one of the heater pins. I cant find a getter anywhere on the tube so I really cant tell if it has gone to air but I am afraid it might have

Can you "ohm it out" to make sure you have the correct pins, and that they have continuity?
With the base cap off, you should be able to see where the heater is connected.

jr

Heater pins should be easier to spot with the base off, but you will need to be sure
that the wire ends are very clean and not coated with the old glue, which is almost
the same copper color.....

As long as you think it's no good anymore, you can try digging out some of the glass
around the broken wire, if you can then solder to it, after you have a good connection,
silicone glue over it..... put it all back and hold yer breath....

.

A good move when re-installing a CRT base is to solder 2-4" of thinner (1/3 the original's diameter is good) wire to the original leads to aid the threading process and minimize the bending the original leads need to line up.

I've had about a 70% success rate even with leads broken off flush
with the glass, if I can get them clean. I glue a #20 wire to the glass with
silicone glue. Soldered to that is a #30 tinned wire that I stick up
against the broken lead. Then I blob that up with nitrocellulose based
conductive silver paint, two or three layer. If it succeeds I cover the area over
with paper and silicone that down. I don't try to silicone over the silver paint.
This may not work with high current filaments. A #30 wire can take plenty
of current if its only 1/4 inch long.

Phil Nelson successfully repaired a broke-off wire on a 10BP4, using silver-filled epoxy. It wasn't a heater wire, though. No telling if this repair would carry heater current.
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