Admiral 14R12 Restoration

[Crist Rigott]

I separated the vertical windings from the VOT and still no HV.

I'm at a loss right now.

I do get a 1/4 long purple arc on the top cap of the 1B3GT tube. So does that mean I have good HV to that point?

Thanks.

[Crist Rigott]

Originally Posted by Kevin Kuehn

Your HV rectifier socket looks charred on one side. Or is that dark black some liquid tape? Or possibly it's just the lighting. It might be normal for the voltages to come up without the load of the yoke on the horizontal fly winding.

Kevin,
The 1B3GT socket is in great shape. It must be the lighting.

[Kevin Kuehn]

Any chance there's a carbon trace that's formed from your CRT's second anode button to the dag? It's a little strange how this problem showed up after switching from the test CRT to the original. I'd even be tempted to check the HV with lead disconnected from the CRT, although I'm not sure it that's a good idea. Maybe old_coot88 can chime in on that thought.

[Crist Rigott]

Originally Posted by Kevin Kuehn

Any chance there's a carbon trace that's formed from your CRT's second anode button to the dag? It's a little strange how this problem showed up after switching from the test CRT to the original. I'd even be tempted to check the HV with lead disconnected from the CRT, although I'm not sure it that's a good idea. Maybe old_coot88 can chime in on that thought.

Kevin,
I switched back to the test CRT a while ago. It was easier to flip the chassis over to get to test points and to help isolate things. With both the regular and test CRT's I get the same result.

I appreciate you hanging in here with me and offering suggestions. Thanks.

[old_coot88]

It's very unlikely that this problem is related to the yoke (if it was, you wouldn't have gotten that healthy arc off the 1B3 connector).

More likely there's a leakage path from the HV source to ground that's lugging down the HV.

First try disconnecting the anode connector from the CRT. Does the HV come up any? If not, then the leakage path is from the 1B3 socket area to ground (and is probably the source of that arcing you heard).

What is the highest Resistance (ohms) range on your multimeter? If it'll go to 20 megohms or higher, try measuring from the 1B3 filament winding to ground. It should show infinite resistance (open circuit). Any indication at all would indicate leakage sufficient to drag down the HV.

Sometimes the insulation on the 1B3 filament winding will break down and arc through to the flyback frame. (The filament winding is one or two turns of thick wire wrapped onto the frame). Or possibly a leakage path has developed in one of the 1B3 socket mount standoffs.

[Crist Rigott]

Originally Posted by old_coot88

It's very unlikely that this problem is related to the yoke (if it was, you wouldn't have gotten that healthy arc off the 1B3 connector).

More likely there's a leakage path from the HV source to ground that's lugging down the HV.

First try disconnecting the anode connector from the CRT. Does the HV come up any? If not, then the leakage path is from the 1B3 socket area to ground (and is probably the source of that arcing you heard).

What is the highest Resistance (ohms) range on your multimeter? If it'll go to 20 megohms or higher, try measuring from the 1B3 filament winding to ground. It should show infinite resistance (open circuit). Any indication at all would indicate leakage sufficient to drag down the HV.

Sometimes the insulation on the 1B3 filament winding will break down and arc through to the flyback frame. (The filament winding is one or two turns of thick wire wrapped onto the frame). Or possibly a leakage path has developed in one of the 1B3 socket mount standoffs.

I disconnected the anode connector from the CRT and the voltage did not go up at all.

I check the filament winding to ground with the 200M setting on my multimeter. It read infinite ohms.

I'm including 2 pictures of how the 1B3GT is mounted and the filament windings.

Is there anyway to test if the filament windings are breaking down? I don't hear any arcing or buzzing or smell any ozone.

[old_coot88]

At this stage I would try to determine whether the 1B3 filament is lighting. In a darkened room, looking upward from the underside of the tube, the filament should be visible glowing a ruddy orange. If it isn't, one of the filament pins may not be making connection in the socket.

Another possibility - the 1B3 may be gassy. Is there a hazy blue glow filling most of the tube? Does it feel hot to the touch after running a few minutes?

[Crist Rigott]

In a darkened room, I looked up into the 1B3GT and saw the ruddy orange glow of the filament. Also there was a ring of blue haze just below the top metal piece that's inside.

I have a bunch or other 1B3GT tubes and I tried at least 4 to 6 others. They all had the ruddy glow and the blue hazy ring.

Because I can draw a 1/4 inch purple arc off the top of the 1B3GT tube, does that mean I have good HV? I'm thinking so or we would be looking elsewhere.

Again, thanks for all your help.

[Eric H]

The blue haze could mean it's got a load on it, I would be suspicious of a short inside the metal cup on the bottom of the socket, my Zenith Porthole uses the same setup and it was tricky to get it back together without problems.

If the new resistors are too fat they might be arcing, also not sure if metal film resistors will work the same as carbon comp in that application.

You might try just popping the socket out of the cup and see if it works.

[old_coot88]

Originally Posted by Crist Rigott

...Because I can draw a 1/4 inch purple arc off the top of the 1B3GT tube, does that mean I have good HV?

It means you've got at least 10-12 KV of unrectified pulse going to the 1B3, which is good. And there should be 12 KV or more of rectified DC coming out of the 1B3, which isn't happening for some reason.

After a few minutes running, is the 1B3 hot to the touch, like uncomfortably hot? If so, there's gotta be a leakage path to ground that's not showing up with the ohmmeter check.

Try removing the doorknob cap so the socket floats free and see what happens.

[Crist Rigott]

OK guys here is the latest checks.

I took the socket out of the metal housing which is attached to the top of the door knob cap. I then used a craft stick to hold it up away from the metal. I also had to unsolder and disconnect the lead from pin #7 that is soldered to the cup. I made a small extension so I could clip it back to the metal cup. I had no difference in my HV.

I then disconnected the wire lead from the metal cup, thus taking the door knob cap out of the circuit and when I tried it, my HV jumped up to about 6800v. There was also a small "squealing" coming from the flyback area, but no arcs were seen in a darkened room. Also I didn't see the blue haze in the 1B3GT tube either. I didn't want to run it much like this. BTW, these tests are done with the test CRT so I don't have the capacitance from the standard 14" tube.

I'm beginning to suspect the door knob cap.

[old_coot88]

It was the doorknob all along, looks like. Good sleuthing bro. The squealing may be the hor. frequency is off. HV may increase further once that's corrected and the doorknob replaced.

[Crist Rigott]

Yeah, I had lots of help with this one. Thanks everybody.

Now I gotta find a new 500pf 20Kv cap!

[WISCOJIM]

http://www.ebay.com/itm/LOT-of-TWO-N...-/112151977376

[old_coot88]

If you want, you can run the big CRT without the doorknob temporarily, since the dag already provides a few hundred pf of capacitance. There'll be a slight voltage drop across the 1 meg resistor, probably not enough to notice.