My CT-100 lost HV (from losing one B+ line).

[dtvmcdonald]

The problem is unobtanium CRT and flyback.

I'm very very afraid of those. I did try it a very long time with the
yoke and CRT unplugged (disables horizontal output and HV) and it never failed. I could try your idea with the CRT only unplugged (both ends),
except I'm afraid for the flyback.

But currently, even with no other symptom whatsoever of a gassy CRT,
I'm suspecting a CRT arc.

[benman94]

Hey I'm just passing along tips and hints from two of the guys that were in RCA's color products division back then... at this juncture there are no questions that aren't worth asking. You're still stumped.

How does the dag look on your 15GP22?

Are you 100% positive the dag has a good solid connection to ground?

Harry had a set (21 incher though) where the connection between the good looking dag and ground was intermittent. The arcing caused excessive HV current draw and had a tendency to pop fuses.

Is your CRT a rebuild? Harry said factory rebuilt 15Gs (ones that never made it through the initial processing) are more failure prone (gas or arcing) but he never explained why....?

[Electronic M]

Originally Posted by dtvmcdonald

I could try your idea with the CRT only unplugged (both ends),
except I'm afraid for the flyback.

There was a tube type (wish I could remember it's number...) that was essentially a 10BP4 gun and base firing into a metal anode that was sometimes used as an HV dummy load in early sets...The 6BK4 and the like were refinements on it IIRC...You could probably use one of those or a 6BK4 connected to the CRT base and HV circuits to sub for the load of the CRT.

[old_coot88]

I once had a somewhat analogous problem with a CTC-36. Someone had spilled a sticky liquid in through the back. It caused a bunch of B+ arcing that had burned deeply into a pc board before the breaker tripped. Cleaned out all the char that was visible, but it still popped the breaker. Several more cleanings and it still popped.

Finally I jumpered the breaker to make the hidden leakage paths visible. They incandesced spectacularly, so I got them all finally.

The rectifier diodes survived the brutalization, but were replaced anyway.

[N2IXK]

Originally Posted by Electronic M

There was a tube type (wish I could remember it's number...) that was essentially a 10BP4 gun and base firing into a metal anode that was sometimes used as an HV dummy load in early sets...\

Sounds like the 5890, which was used as a shunt regulator in theater projection sets. kind of a grandfather to the 6BD4 or 6BK4 types. The RCA production documents describe it as a 5TP4 gun firing into a 2X2A anode assembly. 12 pin "duodecal" base as used on most early CRTs. I have a couple of them in my tube collection. Seriously obscure devices. Handy for load testing the HV on older B/W sets, or for testing a CRT tester....