Mighty Monarch of The Air

[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

[bandersen]

It doesn't look to me like your CRT has any aquadag coating on it - not all do. I bet there's a high voltage capacitor next the the rectifier tube that does the filtering.

The arcing could be caused by component leads or wires coming too close to the base. I recently worked on a Motoorla that had bad arcing caused my a wire coming too close to the rectifier. All I had to do was move it out of the way.

Did you do any work around that area ?

[roundscreen]

xxxxxxxxxxxxxxxx

[vts1134]

Originally Posted by bandersen

Did you do any work around that area ?

I did not. I'm almost positive that the arcing is happening inside the tube itself. I'll fire the set up one more time and be sure.

[vts1134]

Originally Posted by roundscreen

Did they make a set with a glass crt that did not have a ground going to the chassis? Is there a door knob cap connected to the HV rectifier? If not I think you may have washed off the aquadag coating when you cleaned the crt.
From what I see in your pictures I do not see the aquadag coating.
Ed

There is a door knob cap at the base of the HV rectifier.

[roundscreen]

Originally Posted by vts1134

There is a door knob cap at the base of the HV rectifier.

That is the first time I have seen a set with a glass crt that did not have a aquadag coating on it.
Ed

[vts1134]

The arcing is coming from inside the tube, I'm sure of it now. The picture is kind of hard to see because the room was dark but you can see the bluish glow coming from inside the 1X2. Am I right in assuming that this tube is no good?

[miniman82]

Yep, it has air in it and the HV is causing it to ionize. Replace it, and get that HV all the way to the screen!

[bandersen]

Originally Posted by roundscreen

That is the first time I have seen a set with a glass crt that did not have a aquadag coating on it.
Ed

I have several early rectangular 16" CRTs with no coating on them. I'm not sure why though. The datasheets state that they should.

[roundscreen]

Originally Posted by bandersen

I have several early rectangular 16" CRTs with no coating on them. I'm not sure why though. The datasheets state that they should.

That is interesting. Do your set's have a door knob cap connected to the hv rectifier tube? In A set with a metal cone crt the door knob cap goes to ground.
Wonder why are they using a door knob cap in a set with a glass crt instead of using the aquadag for a path to ground?
Ed

[bandersen]

Originally Posted by roundscreen

That is interesting. Do your set's have a door knob cap connected to the hv rectifier tube? In A set with a metal cone crt the door knob cap goes to ground.
Wonder why are they using a door knob cap in a set with a glass crt instead of using the aquadag for a path to ground?
Ed

Yes, they have doorknob caps. So do most of my 10BP4 and 12LP4 sets with grounded aquadag. I guess they wanted the extra capacitance. I think only my cheapo Motorolas rely entirely on the aquadag for HV filtering.

[vts1134]

Originally Posted by miniman82

Yep, it has air in it and the HV is causing it to ionize. Replace it, and get that HV all the way to the screen!

Got a new 1X2 today but noticed that the old 1X2 was a 1X2A and the new one is a 1X2B. The old tube is on the left and the new tube is on the right. Are these interchangeable?

Here is the new tube installed and waiting for a higher intellect to give it the green light.

[VintagePC]

Yep, they should be interchangeable.

Take a look at the letter code specifications - the trailing letters indicate features of the tube. A/B/C are revisions that are backwards compatible, and there are a few others like GT, M etc. indicating glass tube, metal, and some other things.

http://en.wikipedia.org/wiki/RETMA_tube_designation

[vts1134]

Fired the set up and got this.

Fired her down immediately. Is this normal? Just a burn off process or a symptom of another problem?

[old_coot88]

Holy mackrel. Possibly a dead short either in the doorknob cap or from the 1X2 filament winding to ground. oc