More Zenith portable questions
 

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!

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

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.

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.

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

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

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.

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?

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.

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.

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.

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.

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.

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.

I noticed a cheaper device being sold as a 'Digital Video Stabilizer'. Do you think that would work in this kind of situation?

Well, after watching it some more, the picture isn't as stable as I first suspected. It still slowly warps around, with spots getting larger or smaller, and is especially noticeable when a static image is displayed on the screen. I'm hoping when I finally decide to buy that new flyback that that will fix the issue. I assume it's the arcing I hear that's causing this phenomenon by causing the high voltage output to vary, but if there's something else that could be doing it, I'd appreciate any suggestions.

Dont overlook your HV cup that the 1K3? sits in. I have had those with pinholes blasted through. Open HV cage or just remove it, Lift the cup off the chassis.
Hold off on the fly though, it probably will not fix the flag waving on VHS. try the AFC diodes though.

Well, I did already try hot gluing the bottom of the socket where everything connects. That got rid of all the arcing I could see (although the filament winding was trying to arc through its insulation, too -- I took care of that with electrical tape).

As for the AFC diodes, I already replaced the selenium pack with two standard silicon rectifier diodes. Are those unsuitable for this purpose? Should I have gone with Schottky diodes like I've seen people recommend?

EDIT: I'm sorry, you were referencing the VHS problem. I kind of moved on to a different problem when I was talking about the picture locally shrinking or getting larger. It kind of looks like the shrinking and blooming due to brightness problem that all CRT TVs have, but it's doing it even when a static image is on the screen.

By the way, for the Schottky diodes, what reverse voltage and forward current would you recommend? 40V/1A seems most reasonably priced, but I don't want to put them in if that's not a high enough rating.

As for the Flag waving on VHS, VKer Cbenham has a cure: http://videokarma.org/showthread.php?t=257988&page=6
Some of my sets could benefit here.

Oh, that's interesting. I wonder which point I would solder that to on my set? I don't see anything in the schematic that's clearly labeled a 'filter', so I don't know what I would be soldering across.

I can upload an SVG trace I made of my schematic, if it helps.

EDIT: The grid of the 6EA8 tube labeled "Horiz. AFC" has a 1000pF capacitor to ground. Do you think replacing that with one of a larger value would have a similar effect to what cbenham is describing?

You've done two things that seem like EXTREMELY bad ideas to me.
First you tweaked the alignment without a TV alignment generator. It is nearly impossible to get TV RF and IF alignment right by eye alone, and nobody should EVER mess with it unless they have a good TV alignment generator, and oscilloscope, the factory or Sam's alignment instructions for the set to be aligned, and plastic alignment screw and hex drivers(if you use metal ones once you dial in an adjustment, the moment you remove the tool from the slug it will loose the adjustment you made, plus metal ones tend to crack apart and destroy adjustable cores).

Second it sounds like instead of cleaning the HV you just applied hot glue. This is bad on two fronts. Arcing can often be caused by dust and dirt building up and becoming a conductive coating...If that has happened(and you can't usually tell from looking) the glue likely won't do a damn thing to remove the conductive path formed by the dirt causing arcing. Lastly hot glue in the HV cup or almost anywhere on a chassis is a bad idea. The set will eventually get hot enough to melt the glue(especially that close to a tube), and you will have a big mess to deal with when it melts...Also you will have to deal with the the glue if you ever need to change the resistor in that socket or the HV/filament wireing going to it.

On most sets with a plastic HV cup there are two screws that hold the cup to the chassis, and two more that hold the socket to the cup. Remove them all, remove the cup, clean the everliving daylights out of the cup, clean and dust the socket and the cup mounting area, and reinstall the cup. This will solve most arcing issues commonly associated with an HV cup.

You said you wanted to change the HV rect filament wire and HV line to the CRT but could not find a suitable replacement. The cheapest and easiest replacement you can get is to find a 20" screen or larger 1980's-2000's CRT set at the curb or buy one for a couple of bucks at a thrift store/resale shop and steal the HV lead to the CRT from one of those newer sets(I do it and it works great). You may have to strip two sets to have enough to replace both the filament lead and the CRT HV lead. You can use the HV connector already on the lead from the newer set. Patching HV/HV rect filament lead with electrical tape is like putting a bandaid on a gun shot wound....It might help, but it won't stop the bleeding.

I don't mean to sound harsh, but it makes me sad to see you harming a set you seem to really want to have working properly through bad seemingly uninformed decisions.

Ditto to your entire post. Sad.:worried: Wish he had some in-person mentoring for help with it.

I'm sorry man, but I'm doing the best I can with the knowledge and equipment I have. :( I got the set for free, and I hate to spend a lot on equipment to get it working. You're right that I don't have a lot of experience with high voltage equipment. I have it just *almost* perfectly working, and there are just a few small problems I still have to work out, so I kind of just started trying things.

As for the alignment, I just kind of figured I'd try to do it by eye, and if that didn't work (which it didn't, as I shattered one of the cores when I tried to turn it), I'd pipe in composite video. That's what I'm doing now, and it's working great. The point where I tied the video in is at the grid of the video output tube, which is supposed to be a 1V Peak-to-Peak signal, and is DC biased at -0.5V, so the composite video signal is close enough to work, there. I have the audio going straight into the volume control, which DC biased at 0V, but I think it's expecting a higher signal amplitude, as the output is kind of quiet.

I can pick off the hot glue (I've done it on a lot of things before) and clean the HV cup, as you suggested, and see how that works. I do appreciate the advice, even if you have to give it harshly.

I can understand where you are at. My first couple of restorations nearly drove me nuts before TV restoration clicked(and I had spent years working on tube radios prior to that) and my projects finally started to come out right.
A couple of additional tips ANY sharp or pointy edges on the solder contacts or leads going to the HV socket will cause arcing or corona discharge so if you change the HV rect wireing clip excess lead lengths and make sure to solder in big smooth blobs covering wire and component lead stubs completely as well as any sharp points.

As for the weak audio...You can use a cap .1uF or thereabouts should work to couple the line audio from your signal source to a point before the volume control and after the FM detector. If you connect the cap to the output of the audio FM detector that should give you the most volume.

That HV cup should be washed like a plastic dish, then do as I say below.
I did this to the flyback on my 1963 RCA Color roundie back in 1979, and when I fired it up about 20 years ago the HV came up without arcing.(it needs other work including a picture tube) Funny thing, 34 years ago, I assumed I would NEVER find a flyback for this set, so I stripped the arcing-tracked cover off the fly and brushed on about 6 coats of this stuff. I highly recommend it.

When in doubt, get the dope out and start brushing;..http://www.alliedelec.com/images/pro...S/70159781.pdf

Electronic M is right on..
Regarding unqualified alignments, I diddled my share of slugs to compensate for tuner, IF and video problems.:sigh: I recommend getting a fact'ry schematic, scope, marker and sweep gen (Sencore speed-aligner) do it right. It always improves things. I will not tweak anything other than sound, burst or horizontal efficiency coils without the above equipment.

Alright, I cleaned up the HV cup, and I also did my best to smooth out the soldering on the socket (it wasn't pointy, but it did have a couple of lumps). I still hear an occasional arc, but it doesn't seem to be nearly as bad as it did before I put the hot glue on, even now that I've removed all the hot glue.

I'm still getting 'waviness' on static images. Is that just normal, or is there something I can do to get rid of that? It's hardly noticeable while watching an actual TV program, but if, for example, I bring up the menu on my VCR, I can see the text swell and shrink regularly, and it almost looks like there's banding of increased and decreased intensity that 'crawls' up the screen.

Could be bad lytics in the power supply.

Could also be bad fluctuations in your wall current. I have that problem, and it drives me nuts. My sets(when I run two or more at once) will rapidly and randomly bloom at the same time (lights also flicker in step to it)...A friend of mine experiences the same thing and thinks it is because of smelting operations running on the same power grid in the area.

Well, I replaced all the electrolytics with brand new parts I ordered from Digikey when I first started working on the set a couple of years ago, so I guess I'd suspect the wall current. Maybe I could replace the capacitors on either side of the main power choke with larger values and see if that works. 40uF and 80uF seem pretty small, to me, but those were the original values.

Well, since I haven't posted a picture of this thing in a while, here it is, running, outside the cabinet.

I still think maybe I should order that new flyback when I get a chance. I let the TV run for a good long while tonight, and it was doing fairly well, up until a few minutes ago, when I started noticing some speckles in the picture. When I got up close to the set, I could definitely hear a lot of arcing. Since it only happens after the set gets hot from being on a long time, and I can't see where it's coming from, I feel like it has to be inside the flyback. I guess I could try to track down some of that corona dope and paint it on first, if you really think it'd help, though.

Try observing the area of the flyback and 1B3GT rectifier with all of the room lights off (in total darkness). You may be able to spot the arcing unless it is inside the flyback or some other un-viewable place.

Phil Nelson

I also seem to recall from some past thread the suggestion of using a plastic listening tube to isolate the source of arcing that can't be seen...Just because you can't see it does not mean that it is in the flyback.

Also if this arcing has been going on for a while and it was inside the flyback then it should have killed the fly already. On roundy color sets once the fly begins to arc internally it usually dies quickly...The same should go for most flys of that era.

It's gonna be tough for me to track down this arcing. After an overnight cool-down, the arcing is gone again. I guess tonight I'll have to take the chassis back out of the case, take the top of the HV cage off again, and let it run for a couple of hours until the arcing starts back up.

Using a listening tube is a great idea. A flexible plastic tube can be snaked in right next to components.

Humidity affects arcing. It will be worse during high humidity (easy to notice here in the rainy Pacific NW).

Phil Nelson

Alright, I'm pretty sure the loudest of the arcing is still coming from the bottom of the 1K3 socket, even after the plastic cup was cleaned. It's definitely starting to affect the picture a bit, as when I hear the louder arcs, the picture also shudders sideways momentarily. It wasn't doing that a couple of days ago.

You might consider looking for an NOS cup. If yours is not transparent plastic the plastic may have internally carbonized forming a conductive path that can't be fixed or seen.

Nah, my HV cup looks completely clear, now that it's been cleaned. Well, except in the very corners where I wasn't able to scrub (I couldn't even fit a toothbrush down in there).

Aah! Look what I just bought!

http://www.ebay.com/itm/121113874564

I've had a search up on eBay for one of these for a long time now. My yoke is fine, but the rear cover completely disintegrated, so I had to make a new one out of cardboard. This one has the rear cover intact! That's all I'm buying it for, really, but to me, the $30 it'll cost me is worth it (especially since I've never seen the cover separately, except from someone I messaged a while back who lost it before I was able to contact them). I also ordered a bottle of corona dope today to hopefully save my flyback with.