Recently, I've acquired my first Zenith Porthole... Model H2438R from 1951 with the 24H20 chassis.

The wood is in good condition, however the finish is lacking. Most of the finish has come off the top and the base... needs to be sanded down and refinished. No big deal... this cabinet will be pretty easy to make look nice again.

The chassis was very dusty, but a couple of make-up brushes and the vacuum cleaner got things pretty clean. Under the chassis looked pretty good. On top, there's been some tubes changed. Most of the tubes are the original Zenith tubes, and the replacements are all RCA and it appears they may have been all changed at the same time. The flyback looks good.

I suspect it's possible the yoke has been changed. The wires to the yoke were still quite bright with color and little if no dirt. Also noticed the the paint has been broken on screws used for evidence of tampering.

The CRT has been replaced with an RCA Silverama and tests EXCELLENT on my B/K 470! The meter nearly goes all the way to the top of the scale! I really like that! I kinda suspect the CRT may have been changed at the same time as the chassis tubes.

The guy I got it from told me he bought the set 15 years ago, and has turned it on from time to time. He said he quit turning it on five years ago when the power cord's insulation start cracking and falling off.

I'm considering pulling the HO tubes and bring the chassis up slowly to see if I can get any life out of it, and if all goes well, plugging the HO back in to see if there's any light on the screen. Of course, the chassis will get recapped, but being that everything looks good, I'll attempt getting a raster only for a few seconds and then shut it down.

I need some input from others that have dealt with metal/glass CRT sets. At the front of the CRT, there's a big grey rubber molding around the edge. I'm going to assume that this molding acts as an HV insulator between the CRT front lip and the metal bezel on the front of the cabinet. Being that the front of the CRT is only about an inch from the rear of the metal bezel, I'm guessing that rubber molding keeps you from getting zapped by the front of the set. Right?

I notice that my Raytheon Porthole set uses this same rubber molding in the same manner.

Here's my concern: The rubber molding around the CRT front has developed several cracks (see photo). With this in mind, I'm afraid there could be some HV leakage and cause an extremely unpleasant shock from the front of the set. After Dave's recent enlightenment, I'm reminded to pay close attention and be very careful.

Question: Am I putting way too much thought into this, or am I right in assuming I'll get a jolt? If I am indeed right, I'm seeking suggestions on how to remedy this molding issue.

Congratulations on the nice acquisition! Sounds like you really lucked out getting a great CRT.

I haven't started working on my porthole yet, so I don't have actual experience; but your fears sound well grounded. ;)

Actually, is the bezel grounded? If so, you should be safe from the front.

John

You are correct in assuming that if the insulator bezel around the front of the crt is defective you could get a jolt if you are grounded if the front trim ring around the safety glass is touched. To check if you have a problem, simply take an insulated wire and ground one end to the chassis and then touch the other end to the metal trim around the front of the set. If the metal trim is "live" you will get arcing to the wire.

No arcing=you are probably OK

The front bezel is not grounded (that I noticed), so I will try grounding a wire to the chassis and touching the other end to the front to see what I get.

I might see if I can fill in those cracks... perhaps with some silicon caulk. Too bad it's clear instead of grey. I think I can do a neat job with that, and perhaps prevent an episode! Another thought would be to use an expoxy (such as jb weld) to fill the cracks. That's grey, and would likely serve as a good insulator.

Another thought would be to remove the molding and wrap the front lip of the CRT with electric tape (at least a few layers) and then replace the molding.

I'd prefer not to leave it as is (even if it doesn't seem to cause a problem) being that the cracks could get worse over time... increasing the chances of a zap.

As an added precaution, I could also ground the bezel to the chassis from the inside. If leakage did eventually occur, it appears there's a fuse in the HV section, and that would blow if things got hairy.

The black rubber surround around my 16" is cracked/very wrinkled also (very ugly)... does anybody make a replacement part? I am surprised that Zenith did not ground the bezel, but mine does not appear/measure to be grounded either.:no:

jr

What size is that tube?
I have a good insulator but it's for a 12" set.

Thanks, Eric, but this one has the 16" tube.

I have never tried it, but always thought that I might be able to cut a reasonable replacement from a small bicycle inner-tube :scratch2:

Any other ideas?

jr

Jr, I could take your inner-tube and simply line the inside of the molding... that would also work just like the elect tape... but maybe provide as a better insulator! :yes:

I'm still jealous...I've Lusted Mightily for a Porthole Zenith for quite awhile now...There's just something SO "1950" about them...1950 was sort of in an earlier age, but by '59, things had REALLY changed....

That's a nice find Charlie!!

Another thought may be, once you are ready to install the chassis in the cabinet permanantly, seal the cracks with automotive grade silicone of the correct color. I would go around the entire front to maintain consistancy.

Nice find :thmbsp: I think that's my favorite model of porthole. So much easier to move around than the giant combo units.

I was trying to think of some other rubber gasket similar to that and it occurred to me that some washing machines have a grey rubber gasket that is seen when you open the lid. There could be a useful one from an old machine or even take the Zenith gasket to a big appliance parts store and see if they could come up with something similar. Even if the right profile gasket was too large a diameter, a piece could be cut out to reduce the size. It might mean reusing the old gasket and just using the new one for cosmetics out front.

Good one! perhaps far easier than cutting up bike inner-tubes. Perhaps another possibility is visible in Charlie's avatar... a REAL Porthole! Do those things have gaskets? :scratch2:

jr

How about the foam insulation used on water pipes? It's gray, comes in a variety of sizes and is easy to work with. You know what I mean...about 3' long, slit down the side to allow fitting over pipes?

I've got that same 1950 set in a blond cabinet. It too has a few cracks in the gasket.
Terry

Wow... I've got all kinds of ideas to consider and try... thanks guys! I appreciate all the input!

Although it won't work, I like Jr's ironic thinking- use a gasket from a real porthole! Yes they do have gaskets, but they're just O-rings and not very thick. The glass, however, must be at least 3/4 inch thick... maybe even a hair more. I brought one of those old portholes home years ago... it was a gift for my brother-in-law who likes to make things out of neat stuff. That thing (with the brass frame around the glass) was HEAVY!!

The bezel was originally grounded to the chassis in one of two ways: hard wired, or a spring wire that contacts the chassis when installed. The spring wire will be secured at the channel escutcheon, or the hard wire from the volume escutcheon to the same point where the power supply is grounded.

I will take a closer look next time I pull it out. Perhaps there's a spring in there and I simply didn't see it. Thanks, John.

Charlie, I've about completed a restoration of a 1950 model Zenith Porthole. The whole saga is documented on www.AntiqueRadios.com under the Television forum.

Your first post peaked my curiousity in regards to HV -- "After Dave's recent enlightenment, I'm reminded to pay close attention and be very careful." Could you enlighten me on this?

I never even gave it a thought of potential HV shock from the front bezel until I started reading your thread. After reading this, I did post a picture of a wire on the front bezel that I wondered about and your posting showed me what it was.

CW

CW: Dave got :yikes: ZAPPED :yikes: recently while having his hand in the back of a set... sounds like it wasn't very pleasant. :no:

Sometimes, we need little reminders to keep us in check when it comes to playing around or near high voltage. At Dave's expense, his recent experience was my little reminder. Oh yeah Dave, thanks for the reminder! :D

In addition, this Zenith has one of those metal/glass tubes that has the entire bell charged, so I have to keep in mind about being extra careful. I haven't worked with too many of these tubes. I could easily see someone (someone being myself) just reaching in there with the set running to grab something. because that's what that person is used to doing. As like most people, I really just don't like pain. Pain sucks. :tears:

STILL have some pain it my upper arm from that, I just hope it will eventually go away... Yea I have def new respect for HV, its one thing to hear you guys talk about it, but a whole nother level to exp 1st hand.

Shocks like that can even break bones when the muscles contract. Though I doubt that TV HV supplies enough current.

John

STILL have some pain it my upper arm from that, I just hope it will eventually go away... Yea I have def new respect for HV, its one thing to hear you guys talk about it, but a whole nother level to exp 1st hand.

So far I have not been zapped by my Porthole TV, but I know its only a matter of time. Just the other day I did something really stupid. I have an AC line cord with aligator clips for test powering my chassis. Absent minded me the other day plugged the cord in the wall and I picked up the other ends without thinking. Instantly I came to my senses and dropped the ends and unplugged the AC end. Luckily I was not shocked - but like I said it was simply luck that I was not shocked. Its easy to get so involved and not think about safety first.

But, I have been shocked by the CRT anode back in the 1970's and my reflexes literally knocked me across the room and out of my chair. Luckily there were no long term affects, broken bones or lasting pain.


CW

While tonight's game was playing, I decided to try a soft start of the Zenith. So far, I've done nothing to the chassis other than clean out the dirt and give it a visual inspection. Hooked up a couple of meters to monitor B+ and spent a couple of hours bringing up the juice. Kept feeling cans to see if any were getting warm, but they all stayed cool.

By the time I got up to 60 volts, I figured I'd start to hear a little crackling thru the speaker, but nothing. It seemed the audio output tube wasn't getting warm. By the time I got to 75 volts, I figured it had to be burned out. Popped in a new tube and then started getting audio from my Dish receiver!

Slowly kept raising it to full power with no problems or issues. The B+ voltages were all looking good. Let it run a little bit longer then shut it down.

Plugged in the horz output tubes, brought the juice back up, and got a picture! Actually, was a pretty good picture other than not being centered just right. Didn't really have to make any adjustments for a lock. After running it for a little while, the verticle did get a little sensitive during certain scenes.

The HV was a little low... paperwork is calling for 10KV and I was getting 7KV. Even so, the brightness was good. I will try a new rectifier and see how that does.

The photos I took aren't so great... this new camera I have does not do screen shots so well... I think it has to do with the automatic setting and my flourescent overhead lights. I miss my old camera. So, it really looks better in person than these photos show.

All in all, I was very pleased to find things in working order with no smoke, fire, or sudden surprises. Considering it's nearly 60 years old, filled with black beauties, and has the original cans, I'm surprised it plays as well as it does. I'm sure once I get the set recapped, it can only get better. :yes:

Excellent!
I used to be really paranoid about power up sets before doing a full recap. Lately though if the set looks OK visually I've been doing more slow start-ups just like you describe with some good results.

I've had a time or two in which something blew. I had a BB cap in an RCA b&w set that blew the casing all the way across the room! Soft started an CTC11 that did fine the first few times, but by the time I turned it on for the fourth time, something in there got really tired and decided it was time to go. Sometimes I think we just get lucky. If a cap blowing is the worst that happens, I guess it's not all that bad.

Damnation, you boys are makin' me Lust Mightily for a Porthole !! The one I'd give Eyeteeth for is a "Claridge", the leather-covered tabletop model. There's one on YouTube, showing Liberace playing "Nola"...Me likey, me wantee REAL bad....(grin)

... Lately though if the set looks OK visually I've been doing more slow start-ups ...

I'll do that to see if the unobtanium parts are good (flyback, CRT, power transformer and such). If I get some activity on the CRT screen, then I can proceed with a recap with confidence that I won't be wasting my time and caps.

:banana:

Things are getting a little better. I changed most of the smaller capacitors this evening, and a few resistors that were a little tired. The picture has opened up all the way, and high voltage is up to the 10kv as the paperwork says it should be... the other day it only got up to 7kv. The verticle was a bit sensitive, but has calmed down now.

Only bad thing is the audio isn't so great. I'm not really sure how great it was the other night as I didn't even turn it up to a normal listening level. I still have more parts to change, so hopefully that part will get ironed out.

I'm waiting on an order of lytics and some smaller caps to come in... likely wont be here till Friday.

Overall, the picture is looking better. I ran the set for an hour tonight during the news with no problems. Even ran a VHS tape on it... not one bit of tearing across the top! :grnbounce :grnbounce

Very cool Charlie, its getting there :yes:

Good work! I hope my porthole looks that good when I get around to restoring it.

John

Things are getting a little better. ...

Only bad thing is the audio isn't so great. I'm not really sure how great it was the other night as I didn't even turn it up to a normal listening level. I still have more parts to change, so hopefully that part will get ironed out.



You've got the hard stuff done. :banana: Audio shouldn't be too difficult to get it working right. One thing to try is to tap the audio signal at the volume control and feed it to a stereo amplifier set (take care to use a coupling cap to keep high voltage out of the stereo). That should tell you if the FM demodulator is working right, and the problem is in the sound audio amp of the TV set. Alternatively, inject some clean audio at the volume control pot and see if the amp works clean.

For audio, the guys at www.AntiqueRadios.com who helped me with restoring my 1950 Zenith Porthole suggested to adjust the BIAS/BUZZ control and the Quadrature Coil. I found that the BIAS/BUZZ control helped get rid of the intercarrier buzzing and adjusting the Quadrature Coil greatly increased the sound volume.

Audio issues turned out to be the two funky flat sand resistors under the output tube. I don't have the right values at the moment, so I put some together to get close values and tacked them in place for the time being. The sound is a lot better now.

I ordered a handfull of 5 and 10 watt resistors with my capacitor order... they'll be here soon. I had planned on changing those particular resistors whether or not they needed it since they kinda fall apart if you're not carefull. There's some others under the main chassis... those will be changed as well.

Looking really good, that's a hot CRT. Does this set have the round/rectangular option switch?

Yes... the switch is located behind the flip-down door under the screen.

It's been pretty neat to watch so far. I like it filling the screen, but, you really miss a lot that way. Being that we're now accustomed to seeing the black bars on top and bottom of so many programs these days, watching it in normal mode isn't so bad.

Perhaps a decent gasket on this eBay bezel?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&Item=380206638307&Category=3638&_trkparms=algo%3DLVI%26its%3DI%26otn%3D2

Not affiliated,
jr

Looks like the rubber is not included. What is seen on the backside of that bezel is the thin cardboard gasket. The rubber insulator would be behind that... actually attatched to the CRT... it's also part of what sits between the lower CRT front rim and the main chassis and is held in place on the CRT by a long spring. However, thanks for pointing it out. :)

I asked the seller if he had the gasket and he just responded back "no it went with the chassis, sorry" .

:tears:

jr

Makes ya wonder about the CRT... it could have been a good one. :sigh:

Great job on the porthole !
One thing I might mention is that I heard one time that JB weld contains some fine metal particals , so you may want to stay clear of it for a insulator ....

Ok, I've been thinking about this insulator situation...Having never seen a porthole in person, about what kind of diameter or thickness would be necessary?
What I have done for various projects is take some automotive type vacuum hose and slit it to fit over what you want..plus, it comes in different sizes. You just have to make sure you slit it as straight as possible for a nice appearence.

So far, the cracked gasket does not appear to be giving any problems. I've run the set several times. Last night, I put new caps/resistors in the power supply/audio output chassis and then ran the set at least 1.5 hours.

As far as the shock hazzard goes, I think I'm safe by simply having the front bezel grounded to the main chassis. However, if this gasket gets worse, I'm sure there's a good chance of HV leakage.

At this point, I'm kinda leaning towards using grey silicon, but I'll give it more thought once I get the rest of the caps put in the main chassis.... which will likely be done today. :yes:

Hey Charlie, Those insulators pop up now & then, so I wouldn't try to sub it with anything else just yet. I've seen many many porthole Zeniths, and only 2 have had brittle insulators. The sets have been in barns, attics, basements, you name it. So, I don't know what causes it. Maybe the supplier goofed and had a bad lot? I do have a cracked insulator that you can have, but wouldn't be worth shipping it. But, I could bust some pieces off of it and maybe you could cut some puzzle pieces to make it look better for now?

John, perhaps I will hold off on trying to doctor my insulator up and just keep an eye open for one.

Right now, I'm trying to figure out a puzzle. I was changing some stuff around the vert osc and came across a tired looking 100k resistor off the plate of the 6SN7 that was reading 1.4 meg instead of 100k. Put in a fresh resistor and ended up with two pictures... top and bottom of the screen. I double checked the color bands on the old one I pulled out... brown-black-yellow... and then put the meter on it again and it was still over 1 meg. Looked at the Sams, and compared to a factory Zenith schematic... both diagrams show 100k... and that's what was in there... just way out of spec.

I went back and tacked in a 1.2 meg resistor, and the picture went back to normal. While I obviously had a 100k resistor that went way up in value, changing it got the oscillator out of whack.

I'll have to go thru the rest of the vert circuits and see if there's something else that's causing this issue.

First, keep in mind the set worked pretty good as is when I first got it.

After changing a 100k resistor that went up in value to about 1.4 meg on pin 5 of the vert osc, I got a double picture. I then tacked a 1.2 meg resistor in series with the 100k and the picture went back to normal.

Checking schematics, they do indeed call for a 100k resistor on pin 5. I then looked for other issues around the oscillator, but all seems well.

The vert hold control checks good within specs.

I checked voltages. If I leave the 1.2 meg resistor in there (that's not supposed to be there), voltages are off. Pin 5 should read about 65 volts... I get 12.5 volts. Pin 3 & 6 (cathodes) should read 2 volts... I get .4 volts. Even though these numbers are wrong, the picture is fine.

When I remove the 1.2 meg resistor and only use the 100k as I should, all voltages become exact to what the paper work says... but yet I get the double picture.

So... question is... should I leave the wrong resistor in there since it produces a perfect picture? If no, then what else should I look for?

While I realize schematics can contain errors, remember that this started because I replaced a 100k resistor that was reading 1.4 megs. In addition, you'd have to be legally blind to mix-up brown-black-green and brown-black-yellow.

Thoughts?

Sometimes the more you change ,the worse they get.

I feel like I've been running around in circles chasing my tail. I can't really find anything else at this time causing the vert osc to lock in a 30 cps when I put the right resistor in there. So, instead of trying to make the circuit "right", I'll just make it "work" by leaving a 1 meg resistor in there.

If I wouldn't have noticed the original resistor being so far out of spec, I would have never known something was fishy.

The Zenith service notes had lots to say about the verticle and sync section of this chassis. It seems they had quite a few issues. The verticle integrator is one of those couplet units. I thought it was simply a disc capacitor at first... then noticed it had three legs instead of two. There's no diagram to build your own.

I know how you feel. I'm having the same headaches with the Sentinel I'm restoring. It was working OK, but I found resistors that were way off from the schematic. I replaced them figuring things would get better only to find they're worse now :(

Hang in there - I figure the hobby wouldn't be much fun if everything worked perfectly the first time around :D

More than once I have put an original component back in, when a replacement made things worse.

I don't know about this particular case, but there are certainly instances where a design change never made it into documentation.

When the component is clearly original, my theory is that the TV must have worked when it left the factory. So if the chassis and the schematic don't agree, my first vote goes for the chassis.

Phil Nelson

It does not help matters much when you start to realize how many differences there are between schematics. As I was going thru my work, it looked as if I mixed up two lytics... put a 40 mfd where an 80 goes, and the 80 in the 40 place. Looking at Sams, it said I did it wrong, and looking at Zenith, it says I got it right.

There were also many voltages between the two schematics that did not match. I lean towards the Zenith schematic as being the right one, but then, they could make a mistake just as easily I suppose.

Currently, I'm looking for the source of ringing in the video. It's not severe, but it's there enough to notice it.