Mighty Monarch of The Air

[vts1134]

Originally Posted by old_coot88

Is the aquadag (conductive coating) on the CRT securely grounded?

Where is this connection?

I may not have wasted any ones time, but it was a forehead slapper for me that's for sure. It sure has been a learning experience on my first set.

[Phil Nelson]

When the CRT bell is coated with aquadag (black graphite-looking stuff), there is usually a pair of thin wiry springs (sometimes one spring) that push onto it when it is fully installed. These connect to chassis ground, often through the metal yoke housing.

If the sound is a sort of faint hiss or fsst noise, it might be corona (high voltage arcing) somewhere inside the high voltage cage. Did you ever open that cage and clean the stuff inside? It's often covered with very fine, sooty dust. Rubbing alcohol cleans it off easily.

If the inside of the cage is clean, you could open it up and briefly power up the set with the room dark. HV arcs look bright blue or blue-white. If you see any, note the location and power down immediately, then investigate.

Phil Nelson

[vts1134]

Originally Posted by Phil Nelson

When the CRT bell is coated with aquadag (black graphite-looking stuff), there is usually a pair of thin wiry springs (sometimes one spring) that push onto it when it is fully installed. These connect to chassis ground, often through the metal yoke housing.

If the sound is a sort of faint hiss or fsst noise, it might be corona (high voltage arcing) somewhere inside the high voltage cage. Did you ever open that cage and clean the stuff inside? It's often covered with very fine, sooty dust. Rubbing alcohol cleans it off easily.

If the inside of the cage is clean, you could open it up and briefly power up the set with the room dark. HV arcs look bright blue or blue-white. If you see any, note the location and power down immediately, then investigate.

Phil Nelson

I remember reading this from your 630ts. When I first heard the sound this is what I thought of so I took a look at the area through the bottom of the set with the lights out and couldn't see any arcing. I'll try looking at it from the top of the set tomorrow and see if I can't pinpoint any arcing.

[vts1134]

Found the source of the noise. It is V18, the high voltage rectifier. The base of the tube is sparking bright light blue. Could this be a bad tube itself, or possibly a fault elsewhere causing the problem? R89 and R95 are both reading right on.
I'm sorry to be such rookie but I'm still don't quite get the ground connection for the aquadag. I've google searched the spring connections and saw a couple of examples but my set doesn't have anything like that that I can see. The only connection that I can see is a rigid wire connected to ground with a u shape around the high voltage wire. Is this supposed to be making a connection for the aquadag, or is it just to hold the high voltage lead in place? I've tried to show as much as possible of the tube in the three pictures below.


This next picture you can see the high voltage lead and the wire I mentioned with it.

[old_coot88]

Huh. By golly that tube does not have an external aquadag coating. That wire around the HV lead has no electrical function, it's just a mechanical support.

At least you've located what's doing the arcy sparky thing.

oc