I'm working on a '48 Capehart. I didn't recap this one, but I respect the abilities of the person who did recap it (a fellow AKer). I had it shipped cross-country via a mover (North American Van Lines) but it doesn't appear to have taken any abuse. It had no CRT, so I put in my own untested used 10BP4. I bought the CRT from a different AKer who said it tests 100%. I think it probably does, but still don't have a CRT tester that I trust. After adjusting the ion trap magnet I get a nice bright screen and full raster. It's a radio/TV/Phono combo and I haven't checked out the radio so I can't say how the TV's audio is (it uses the radio's output stages). The radio isn't recapped yet. The phono is completely missing. The cabinet is rough but complete.

So the TV looks pretty good, but every couple of seconds I hear an HV "snap" and the CRT screen darkens, then recovers. In the dark I'm seeing an arc inside the neck of the CRT at about the point of the ion trap. It seems kind of violent -- destructive enough that I don't want to let it continue, for fear of ruining the nice 10BP4. Unless the 10BP4 is already ruined and that's why it's doing it.

Anybody have any suggestions?

The tube may have a short in it, however the only real way to verify it is to put it on a tester :(

I assume all the voltages at the CRT are ok according to the scat?

I'll confess, I recapped this set, it used to be mine. :yes:

Kirk, how long does it have to run before the trouble starts?

I fired the set up a few days before I took it to your parents house and it worked OK, I didn't run it a long time though, maybe 15 minutes or so.
I Know it hasn't been run more than an hour total since it was recapped.

I can't imagine what would cause an arc inside the tube other than a bad tube or way too high HV?

There are some adjustments down on the side of the HV cage accessble through the bottom door, check and see if there is a HV adjustment?

Might just be a bit of debris rattling around inside the crt that got lodged in the gun? Could try shaking it around...

Yep, it's Eric H's Capehart from here:
http://www.audiokarma.org/forums/showthread.php?t=118767&highlight=Farnsworth
Thanks again Eric for setting me up.

I didn't want to plug in the Beltron CRT Restorer at least until I pop the hood and once-over the capacitors and such. I'll do that today later. Thanksgiving break, I have some spare time for a change.

The problem occurred immediately. In fact first thing I did was forget to put the ion trap on, and with the dark screen it would "snap" and the screen would slightly light up. Soon as I figured out the ion trap was laying on top of the cabinet, I put it on and got the above results. It happens moments after powering on the set (about the usual time for tubes to warm up) and does it repeatedly until I lose my nerve and unplug the set.

I hope adjusting the HV will settle it down, otherwise I hope it's just the CRT (I have a couple of untested parts-set 10BP4's too, but want to test them first once the Beltron is up and running). Will post more later.

That sounds like a bad CRT for sure,Try rotating the CRT around a few degrees and run it that way for a bit,I have done this and it works.:scratch2:

I believe there's a ground wire that connects to the back of the focus magnet, is that connected?

a ground wire that connects to the back of the focus magnet, is that connected?

Also, if that CRT has the agadawg(sp!) coating, be sure that that has a ground as well.

Hey Kirk,

This sounds very much like a problem I had right after purchasing a Sony 17" Trinitron set back in 1977. It turned out to be some kind of power issue and not a problem with the CRT even though it would go dark after the snapping sound. One day it went dark and never recovered, and some very small part was to blame.

While people are in agreement that it appears your CRT may have issues, it would be worth checking your power supply. I know we're talking apples and oranges some 30 years apart, but even with my limited knowledge I know there are certain elements of TV receiver theory that have remained in use since the beginning so your problem could be located somewhere outside of the CRT.

Hopefully one of these days you'll find a Capehart that won't present a nagging problem as you attempt to revive it. They are nice sets.

Ralph

Hi Ralph. If this were easy, it wouldn't be an accomplishment or as much fun. I eventually got my 325F completely working, as good as new. It was really frustrating for a long time but I stuck to it and learned a lot and eventually succeeded. It gave me the confidence to move forward on to other TVs.

Wa2ise, the Aquadag coating is intact and ohms out to all of the chassis sections correctly (it's grounded).

Eric, the focus-magnet ground wire is connected and ohms out correctly.

Wiseguy, you were prob'ly right. Spinning the CRT a few degrees might have worked, but it wasn't easy putting it in in the first place (mounted separately to the cabinet, not to the chassis, in an awkward and hard to reach cradle).

Jordan, I recapped my Beltron CRT restorer today. Very cool device. It had 2 bad electrolytics, 2 burned out bulbs, one bulb vibrated out of its socket, and the interrupt switch contacts were dirty. After taking care of those, I believe it's 100%.

I had a no-emission 12LP4 I tried on the "Admiral Roundie from Hell" last summer and it was just a black screen. I put it in the basement for "someday". I used it as the "guinea pig" for my first CRT restoration attempt. In phase one, it had a 0.1 emission and fell off immediately upon pressing the interrupt switch (no life test). I left it warm up for about 5 minutes and it eventually maxed out at about 2.8 and still dropped off way too fast. I went to phase two and it never lit up the cleaning lights. So I went to phase 3. Three cycles of 85 to 65 (as called for in the instructions). Back to phase two and then phase one. It now has 9.5+ emission and holds the life test for ten seconds. It tests as new. I'm excited about this and can't wait to see its bright picture.

So I tried the same operation on the "snapping" 10BP4 in my Capehart. It cleaned the shorts in phase 2, already had an 8.5+ emission reading on phase 1, so I didn't do step 3. I fired up the TV set. No more snapping, works great.

So my first 2 hookups to the Beltron were 2 resounding successes. Very nice.

Attached is 2 shots of the Capehart. Obviously some linearity issues, but nice to see most of the circuits are up and running.

Will recap the radio this week and get it back in the loop. This set should be a keeper. Eventually. Lots of cabinet refinishing work. But will be nice someday. More later...

Got the yoke leveled. Worked out the linearity issues as best I can with the adjustments available. Top of woman's head just a little flat, forehead just a little stretched. Otherwise excellent. Might go through the vertical section again & look for a weak tube or some such. Probably stop here for a few days and focus on getting the radio up to par.

B&K Analyst has variable gain output, could get a pretty clear (if warped) image. Not so good with regular TV feed. VCR shot of setup screen ought to have been a smooth background, still a lot of sparkles instead. White letters bold and crisp though. Any thoughts?

Sounds like you have poor RF sensitivity. Looks for shorts around the antenna leads and antenna input on the tuner. If this has a safety cap(s) between the antenna connection on the cabinet and the ant-in on the tuner it could be bad. It will most likely be a small ceramic.

If you have the sams alignment procedure, check the output of the tuner and IF tubes to see if all stages are working properly. Since you have a sharp picture your video detector and amp stages are probably fine.

FWIW when I capped that set that's all I did, slapped caps in it, fired it up and got a picture and that was it, it's hasn't had any resistors checked, tubes checked or sockets Deox'd, tuner cleaned or any of that stuff so that might be a good place to start.
Nothing was done to the radio at all, it more or less worked as-is but seemed weak.

Edit: I may have checked the tubes but it's been so long I can't remember.

Imagine watching a World War 2 documentary on that thing.

And for contrast, somehow hooking up a modern day DVD player or game console to it...

I wasn't expecting a brand new TV. If everyone here doesn't already know it, I'm picking up one of Eric H's abandoned projects. The work he did on it is high quality, just unfinished. I'm thrilled to have it in any condition. I consider the electronics to be in great condition. Just working out the last few bugs.