Zenith 19L25 Chassis Restoration - Advice? - Videokarma.org TV - Video

RitchieMars · #1 08-27-2010, 12:53 AM

I think I'll be getting started on my Zenith L1846R sometime soon, so I've been sorting out the parts list I'll need to put together. I already have a good list of all the capacitors that are gonna have to go, but while I was at it, I went ahead and checked around on the resistors, too. Among other things...

Here's one thing that I decided to get out of the way early:

The original plastic cover over the yoke had deteriorated and created a mess of black shards that I'm still finding all over the place. Testing those resistors was getting pretty boring, so one night I decided to make a cover myself. It's just a bunch of thin card-stock type paper from a folder rolled up, cut, trimmed, and coated in duct and electrical tape. It holds my magnetic rings nicely, but I'll want to go back and seal this thing over with something heat-resistant. Plastic coat and engine paint should work.

A fellow told me that he remembered these sets having faulty screen resistors near the horizontal output tube. I found a bunch of resistors going from pin to pin that aren't listed in my schematics:

I found one resistor in the parts list that was called a "screen resistor." It was a 200 ohm resistor. It's way over by the tuner stuff, though. There's another near the horizontal output tube that looks similar but I haven't figured it out yet:

Both those read very little resistance.

Here's something else I haven't seen before:

Schematic calls it an "integrator." Looks just like a ceramic cap with three leads.

I also noticed that the getter on my horizontal output tube looks a little hazy...

And now, something I really need some advice on: My flyback!

Looks kinda grody. Doesn't help much that it was right in the path of those falling chunks of plastic from the yoke cover. This is the first time I've popped the cover off the top of the high-voltage cage. I only managed to clean up around the 1B3 before because I could reach it from the back and it was covered in smut. But, the flyback itself is surrounded in filth and seems to have a coat of wax peeling off, which you can see there in the picture. I've read that getting dirty and falling apart like that can lead to serious problems. I hope there's something I can do to clean it up and keep it in one piece!

***Eric H*** · #2 08-27-2010, 01:36 AM

That resistor with the coil around it will check really low, you are measuring the coil mostly and not the resistor.

The black things with the color bands are capacitors, Black Beauties, Bumblebees, whatever you call them, they need to be replaced.

I wouldn't worry about the integrator or the resistors at this point, I would recap first then check resistors if you have any issues.

The flyback needs to be re coated with something, most Zenith Flys seem to be cracking and flaking even when they work OK.

I'd probably clean off that old wax and then coat it with Low Acid Silicone Rubber. You have to be very careful not to break off any of the very fine wires while you're doing it of course.

This stuff here works good for insulating too:
http://www.aervoe.com/paints_coating...y-Coating.html

RitchieMars · #3 08-27-2010, 01:51 AM

Thanks for the advice on the flyback! Yeah, I need to figure out how to get this out of there safely so I can clean it up. It's only got two screws that hold this assembly under the chassis, but past that there's just the wires leading to it. They go through some tight rubber fittings and have to be pulled through partway just to get the flyback loose from underneath but it only comes out so far. I'm not sure of a good way to undo those wires other than unsoldering them from the flyback, which seems iffy since I'd have to get a soldering iron so close to all that wax.

I'll find a way to get to this so I can clean it up and coat it. I presume this flyback was fine. I was able to get a perfectly squared image that filled up the screen before, but there was no sync any which way. Also no sound.

But yeah, I just was poking around through these resistors in the meantime because I knew I'd have to place another order again later if any were bad so I wanted to see if there was anything that stuck out to me in advance. So far, only two that seem to be out of spec. I did find an annoying number of bumblebee's in there. In total, I think I have about 37 caps to replace.

RitchieMars · #4 09-08-2010, 03:22 PM

First, as I go about ordering the electrolytic caps, I noticed that a few of the value's I need for this set are out of stock. I can order the same value of the next available higher voltage rating, or exceed the value without having to go up and thus save a bit on price. I've read that it's safe to exceed the capacitance value in radios, so is that still fair game in a television set like this?

Also, where do I find a power cord? Simple issue; replace cord. But, I really, seriously, have no idea where to get one for my television. It's a simple brown cord, non-polarized blades, and the end that goes to the set has a plastic piece with two female ends ( like what some call a figure-8 ) and it has tabs with holes as if to use screws or rivets on either side. My cord wasn't screwed or revetted, but simply flopping around in an interlock. Don't like it.

It's stuck in there, so I guess I'll have to drill the rivets that hold the interlock together to the back cover, but I still don't know where to find a proper cord. I've tried searching for it online, but I don't know what I'm looking for? Not too keen on power cords...

marty59 · #5 09-08-2010, 08:50 PM

If the cord is in otherwise good condition, don't be concerned about it. It should "float" in it's mounting to help facilitate the installation of the back, and the alignment of all the back's screws while at the same time confirming the mating of the cord to the chassis.

Hopefully, you should have some spare (loose) cords for troubleshooting, otherwise known in the trade as "cheater cords".

If you do need one maybe Moyers or Mock Electronics for starters will have some NOS ones. I've got quite a stash of 'em so I really haven't given it much thought as to where to purchase them anymore...

PaulOF · #6 09-09-2010, 12:11 AM

In the late 50's-early 60's Remington electric razor cords made perfect cheater cords for many TV brands.

RitchieMars · #7 09-09-2010, 09:25 AM

The original cord is partially cut in half. I had it patched up just to test it before, but I need a correct replacement, or at least a brown cord that's compatible. I have cords that will work crudely for testing, but I don't want to be stuck with any of those as a final solution. So, I'm just keeping my eyes out for a NOS or at least something close. I'm not picky about originality, just appearance. The old cord didn't even say "Zenith" on it. Just "Phalo, USA" whoever that was.

Phil Nelson · #8 09-09-2010, 09:59 AM

Quote:

Originally Posted by RitchieMars

I've read that it's safe to exceed the capacitance value in radios, so is that still fair game in a television set like this?

Using the next higher value should not be a problem. For instance, substituting 33uf for 22 uf is OK. The higher value may be a little larger physically. I would not go more than twice the spec'd value. Check the B+ voltage after you're done recapping to make sure it's within reason. A little higher than spec'd is OK (pretty common, actually, since line voltages are somewhat higher now).

Phil Nelson

RitchieMars · #9 09-09-2010, 04:26 PM

Alrighty. Well, I couldn't find a 40uF in a voltage rating I needed, so I went up to a 47uF in those cases. Oddly enough, I found a 4uF rated at 550v in my parts list, but in the schematics, the circuit legend, and in the television itself on the cans, the corresponding filter cap was actually labeled as 4uF at 350v. I guess it was a typo. It made the difference between a $1 cap versus a $4 one, so I'm glad I noticed it.

RitchieMars · #10 09-22-2010, 04:07 AM

I started recapping the set yesterday and I got a good bit more done today. Nothing but a couple bumblebee's and the electrolytics left. I noticed that one of these 47uF's I've got will replace a 40uF that appears to be first in line to the 5U4G low voltage rectifier. I recall hearing that exceeding the original capacitance rating of filter capacitors closest to the rectifier could overdraw the rectifier during the start-up surge. The 47uF's are all I could find, and it's only 15% off. Cause for concern? Just thought I'd get a second opinion on this.

jeyurkon · #11 09-22-2010, 07:26 AM

It won't matter. You'd have to be off by a huge amount. 15% is still smaller than the normal tolerance of electrolytics.

John

RitchieMars · #12 09-22-2010, 03:00 PM

Ah, well that's good. I had figured as much, but I thought I'd make sure. I've replaced about 26 capacitors so far, so I've got less than a dozen left. It's getting close to that time... about to find out if she glows or blows.

UPDATE:

Almost there... 5 more electrolytics and a couple hard-to-reach capacitors still left to go.

RitchieMars · #13 09-23-2010, 05:08 AM

I finished recapping my Zenith tonight and was ready to test it out with the new CRT, but I now have reason to suspect that the rebuilt CRT I bought awhile back isn't really a 17LP4. While it does look nearly identical to the original, I'm having problems getting it to fit in the cabinet properly. I've managed to get it inside, but it looks "different" once you get it in there. I can see the edge of the black frame that supports the CRT more than before, and it looks higher up with more of a gap at the bottom. Worse still, is the fact that the shafts of the switches don't stick out as far as before, and I can't even get my power/volume knob on far enough to keep it in place.

I don't know what to do, honestly. I've been working on this all night, and I'm exhausted. I've pulled that chassis out 3 times so far, and I still can't get it right. Guess I'll try and figure it out tomorrow...

leadlike · #14 09-23-2010, 09:17 AM

It's possible that your rebuild started life as a different tube #. These early square crts went through a few changes in geometry as they went through various manufacturing changes.

I know my 17" Sentinel is a real pain to get back in the cabinet, showing the exact same symptoms you describe. I just really have to mess with it to get the mask to line up right, or else the controls won't stick out far enough.

Right now, though, I would just focus on seeing that your tv is working before fussing over this setback.

RitchieMars · #15 09-23-2010, 12:38 PM

Yeah, I was putting off my initial testing due to the fact that I was too tired to fool with it, and I was hoping to tuck the chassis back in the cabinet to clear up some of the clutter I've accumulated working on all of this. I'm excited to see how it's gonna work, but I never did even test fit this new CRT when I got it so I wanted to make sure it would work out. Looking back into it today, I should have no problem. Even putting the old CRT back in renders the same symptoms so I know it's probably a minor adjustment that I've overlooked. If the tube is in fact that much longer, the yoke can be adjusted from front to back about a half of an inch. So, I'll keep that in mind.