More Zenith portable questions - Videokarma.org TV - Video

jmetal88 · #1 05-04-2013, 10:01 PM

Hi guys,

Today I dug my Zenith C1415U back out of the closet and started work on it again. I have a couple of glaring issues that I need to sort out before using this for any length of time.

First of all, I've noticed the contrast control gets really hot, like there's more current being drawn through it than there should be. Not sure what's going on there. In fact, the potentiometer actually seems to have burned through by now. I replaced it with some static resistors for testing purposes (and because it uses a really odd potentiometer with a 2/3 tap on it) and they get really hot, as well.

Second, the flyback transformer is arcing just very slightly. It starts out fine, and then gets worse the longer the set is left on. I guess it's heating up and melting the insulating wax or something. Since I can't seem to find a replacement anywhere, is there someone on here who could re-wax the thing for me, using that vacuum method I've seen online? I don't have any of the equipment necessary to do the job myself. I had tried coating the thing with liquid electrical tape, but since that didn't seem to work very well, I went ahead and peeled it off. The arcing is both audible and is evidenced by instability of the picture.

If anyone has any advice for me, I'd really appreciate it. Thanks!

Phil Nelson · #2 05-04-2013, 11:01 PM

Have you tried Moyer?

http://www.moyerelectronics.com/Depa...-TV-Parts.aspx

Sometimes you can spot an arc if you turn off all the room lights (total darkness) and play the set briefly. That may give you a clue where the problem is occurring.

If a flyback is shorting internally, I don't think coating the outside will help. Wax isn't the greatest insulator, anyway. That's why they quit using it when better materials became available.

Just my $0.02.

Phil Nelson

jmetal88 · #3 05-04-2013, 11:40 PM

I think I did send Moyer an e-mail last year, when I was concerned that the flyback might not work at all. If I remember correctly, they had one, but wanted $60 or $70 for it, and I honestly couldn't (and still can't) put that much money forward to get this set working reliably.

EDIT: Nevermind, I found the e-mail. It was only $40. It's still a bit of an uncomfortable price for me, but not as bad as I was remembering.

jmetal88 · #4 05-05-2013, 12:11 AM

I went ahead and sent them another e-mail, to see if they still have the flyback. It wasn't the original, but a replacement by Merit, HV0-176. Hope it works. I also asked if it's the same pinout as the Zenith flyback, or if I'll have to hook it up like the Triad that's listed in the photofact.

Do you think the problem with the contrast control might be alleviated with a properly operating flyback, or do you think there's something else going on there? I haven't worked up the enthusiasm to insert an ammeter into the circuit and see what's going on with the current, yet.

cwmoser · #5 05-05-2013, 05:06 AM

I had a heck of a time with arcing in my Zenith Porthole TV.
Turned out that the arcing was between two pins in the 1B3 socket
and continued across the phenolic board to the chassis.

Replaced the 1B3 socket with ceramic (thanks to the forum member who gave me one)
and then cleanned and drilled out the carbon on the phenolic board.

When I pulled the 1B3 tube, I observed a carbon trace between two pins -- check your 1B3
and areas on the phenolic board. Might have to clean the phenolic board of all the
decades of duct and dirt.

Then, I when I reinstalled the new 1B3 socket, I was not careful about sharp points.
My first attempt at a TV restoration and I was learning.
I had to go back and cut off the resistor and wire tails, blob a smooth coating of
solder, and paint Corona Dope on some places.

I did not find arcing inside my Flyback.

Carl

jmetal88 · #6 05-05-2013, 11:46 AM

Hmm, my 1B3 socket is mounted inside a plastic cylinder, so I hadn't thought about it being a possible source of arcing.

I think you might have mis-read my title though, as I'm referring to a Zenith portable, not a Zenith porthole. I don't even see a phenolic board in mine.

cwmoser · #7 05-05-2013, 06:20 PM

Quote:

Originally Posted by jmetal88

Hmm, my 1B3 socket is mounted inside a plastic cylinder, so I hadn't thought about it being a possible source of arcing.

I think you might have mis-read my title though, as I'm referring to a Zenith portable, not a Zenith porthole. I don't even see a phenolic board in mine.

Sorry, you are right - I posted thinking it was about a Porthole TV.

Good luck.

Carl

jmetal88 · #8 05-05-2013, 08:43 PM

I think you might be right about the 1B3 socket though. I turned off the lights and peered into the HV cage with the lights off, and while I couldn't see all of the arcing that was going on, the ones that were bright enough to see came straight from the bottom of the 1B3 socket, and went up over the edge of the plastic cylinder. I'll hot glue the bottom of the socket and see how much of a difference that makes.

jmetal88 · #9 05-05-2013, 09:30 PM

Okay, I took care of all the arcing I can see, but after the set has been left on for a while, I can hear a steady 'crackle' of arcing that I can't see anywhere, so the flyback may still be a problem. Also, I think I might need a new 'suction cup' lead, as I did actually see one arc shoot straight through the insulation on that thing, which is kind of worrying. Any suggestions on where I could find one of those?

jmetal88 · #10 05-05-2013, 11:01 PM

Ah, damn it, I just tried to get the tuner in slightly better alignment, and I broke the core of the first video IF coil. My Photofact doesn't list any replacements other than the Zenith original, so I'm not sure what I can do with it now, with the exception of disabling the tuner and effectively turning the set into a video monitor. I can't find the part number anywhere online.

jmetal88 · #11 05-05-2013, 11:10 PM

Do you guys think this coil would work?

http://www.ebay.com/itm/Meissner-17-...-/261193345646

My Photofact says the coil I broke is a 1st Video IF with a 41.25MC trap.

EDIT: Whoops, nevermind. It's L2 that broke, not L1. It says that one's a 39.25MC trap and a 47.25MC trap. I have no idea about that one.

jmetal88 · #12 05-06-2013, 12:31 AM

Ha, I was able to get a viewable, albeit not extremely clear, picture and sound by seriously misadjusting the other inductors on the board. I'll pretend I'm satisfied with that, for now, haha.

jmetal88 · #13 05-06-2013, 12:43 AM

And some good news: I probably had the TV on for around an hour just now, and it seems like it actually runs fairly stably now. Apparently the smaller arcing that I can hear but can't see isn't really affecting the picture stability. Also, the resistors I was using in the contrast circuit to replace the burned out potentiometer didn't burn out themselves, so I suppose that's good. I didn't feel them to see if they got hot, but if they did, they cooled down fairly quickly, as they're room temperature now.

jmetal88 · #14 05-06-2013, 07:12 PM

I ordered the new contrast control this morning. It was only $6, but shipping was also $6, so it cost me $12, total. I think it'll be fine, the old one probably just burned out due to being in bad condition in the first place. The fixed resistors I have in the set now seem seem fine, even after extended use, and they have the same power rating as the potentiometer. Having fixed contrast is no fun, though, haha.

jmetal88 · #15 05-06-2013, 08:05 PM

Alright, time for another question! What do you need to do to get VHS tapes displaying properly on one of these sets? I found one suggestion that the Horizontal AFC diodes should be replaced with Schottky diodes. How well does that work? I already replaced the selenium diodes with modern silicon diodes, but they aren't Schottky diodes. The other suggestion I saw was to get a time base corrector, but those seem to be really expensive. Basically what's going on is that the very top of the picture is severely skewed on this set, but displays just fine on a modern TV.