Tech-Master NIB TV Kit #5516

[Crist Rigott]

OK, I cut the crimped end off of the sleeve and slid it home. Then I tied it off with some lacing cord. Not as goofy as I thought. It has to be used to prevent arc over because the HV is exposed on the end of the door knob cap.

[Crist Rigott]

Wahoo!

[kvflyer]

Kinda looks as though it works! Congratulations, nice work.

[Crist Rigott]

Thanks KV.

[Crist Rigott]

OK, first problem.

I can't get the CRT into good focus. The yoke is pushed all the way forward up on the CRT. This is an aluminized tube so no ION Trap.

HV is shown at 11KV on my unreliable HV probe.

I did notice this statement from the GE datasheet for a 21FP4/A/C, the CRT I'm using is a 21FP4C. It states having a minimum resistance on Pin 6 (Focus) and Pin 10 (Grid 2 B++). See attached photo. This TV does not have a minimum resistance on pin 6. it goes directly to B-. Should I have at least a 100K resistor in there?

[Crist Rigott]

At another persons suggestion, I tried taking pin 6 (Focus) from B- to B+ 130v and to B++ 300V with no joy.

[old_coot88]

Compliments once again on your outstanding workmanship sir. But offhand, it seems a minimalist, low-B+ design chassis trying to drive a large CRT is not going to deliver optimum performance, particularly with only 11KV on the anode (if your HV meter is correct).

Try this for a moment.. short out the resistor feeding G2 (screen grid) of the 25CD6 to raise G2 voltage a bit. See if this improves HV, width and focus at all. If it does, it suggests that a higher B+ supply voltage on the H output/damper circuit would improve performance. If it doesn't, then maybe a smaller CRT would work better with this chassis.

[bandersen]

Originally Posted by Crist Rigott

...This is an aluminized tube so no ION Trap.

Just because it's aluminized doesn't mean it doesn't need an ion trap magnet. The data sheet says you need a single ion trap magnet. Don't see any exception mentioned for the "C" version. Also is it a rebuild ? If so, it might have a straight or bent gun.

[Crist Rigott]

Originally Posted by bandersen

Just because it's aluminized doesn't mean it doesn't need an ion trap magnet. The data sheet says you need a single ion trap magnet. Don't see any exception mentioned for the "C" version. Also is it a rebuild ? If so, it might have a straight or bent gun.

Bob, yes it is a rebuild. It does have a straight gun and it has 2 labels warning not to use an ION trap.