16" Zenith roundie
 

Just picked up a 16" Zenith Roundie and would appreciate some feedback on how to get the chassis out of the cabinet. Is it possible to slide the chassis out while the CRT remains in place? I took off the Ion trap and I can see that if I took off the spring wire that's joining the chassis to the CRT metal frame it might be possible to just slide off the focus coil with the chassis. The CRT cap was Knocked off at some point but all five leads are still intact. Just don't want to take any chances of further damage at this point. This is a two chassis set. I've already taken out the lower unit. 24H20 &24H21 Chassis.

thanks

You would have a bigger chance of damaging the CRT by trying to remove it separately. There is no other support in the cabinet. All the CRT support is on the chassis.

Thanks It came right out. Much easier than I expected.

I have a restored Zenith porthole TV - 16".
Mine uses the 16EP4 CRT.

BTW, if yours is like mine, there is a slide switch you need to unscrew from the front escutcheon before removing the chassis.

Carl

Mine doesn't have the switch. The first thing I did this morning was to go out and see if the CRT at least had continuity through the heater. After scrubbing the probe ends against the wires sticking out the neck I finally got two to show a short. At least I know that the heater isn't open. I made a little diagram of the long leads and short leads assuming that the short ones were probably not used originally. I compared my sketch with a end cap diagram that I downloaded for that tube. To my surprise they didn't match up. One the cap diagram all the leads are in a row all five. On the tube the two heaters are well apart from the grid and bias leads. This is where thing could get ugly. I'd like to put the cap back on but unless someone knows how to get the right wire in the right cap pin I'm stuck.

I suppose that it's possible that the Heater is open and that the short I'm getting is something else shorted inside the tube but for now I'm going to assume the two shorted leads are the heater leads.

I have a 14" with the switch like yours. It's pretty cool switching from full roundie to the trimed view. Both work equally well.

The seller pulled the CL add before I could capture the pics of the 16" so I'll have to get some up here to show. When I got the 16" home and compared it to my 14" the 16" has an identical cabinet with the exception that the 16" is two inches wider. That cabinet really filled up my trunk and that's saying a lot.
The trunk on a Crown Vic is huge.

BTW, Carl, you are right. I found out long ago that there is that little slide switch. I managed to pull the guts right out of the switch by the wires the first time I removed the chassis. :(

But it is a common slide switch and mine went back together with no problem. I would guess that pulling that switch apart several times would necessitate replacement though! ;)

Yep, done that too:-) First time I extracted the chassis from my Porthole TV, I took my TV outside because it was so filthy. I pulled the chassis yanking the small knobs off and pulling the wires off the slide switch. I lost the knobs in the grass but found them the next day after realising they were missing.

These Zenith Portholes are very desirable TVs and I found a lot of fun restoring.

Carl

I made a diagram of the end of the CRT as best I could make out by looking through the tube neck. Hopefully someone can tell me which lead goes to which cap position. I can see that the two heater leads would go to 12 and 1 but the others I have no idea. What is the "A" designation on the Sylvania drawing? Is the grid closest to the end of the neck G1 or G2. Also curious about the short lead that's attached to the grid. Thanks in advance.

I have always only seen CRT connections go straight from the glass into pins on the connector. Your CRT diagram would be the first one I have seen where the wires do not match up. The nearest I would guess is that the three adjacent long wires go to pins 10, 11, and 12, the next one to pin 1, and the last (clockwise) goes to pin 2. Do you have a CRT tester, particularly one with a "universal" adapter that has wires with clips? You could try it to verify the connections I described.

"A" on the Sylvania diagram is the anode (the high-voltage connection, in this case the whole cone of the metal CRT).

UPDATE: I just looked at the gun of my 5AXP4 test CRT that has the same base as your 16GP4 (and all of the other early B&W CRTs), and it does not have connections that line up with the pins on the base either. The physical order of the gun elements from the base toward the face of the tube should be cathode ("K"), G1, and G2, with focus beyond G2 if I remember right on CRTs that have a focus connection (not on this CRT).

I haven't seen that many CRTs without the connector but the few that I have seen all came out streight also like you are saying so that's what's confusing. The conncetor and the CRT look to be original. My CRT tester doesn't have the universal adapter unfortunately. I did do a continuity test on the two heater leads and it was a short. I'm thinking I could possibly add some credibility to the drawing by doing some more continuity testing for example all the leads that go to G1 (the lower grid in the drawing) should if the drawing is correct short together but not short to the heater leads and so on.

Ok I'll check that out and see how it fits.

should there be one or two leads per gun element?

Usually only one long lead per pin...

Pretty much all the large based tubes have the two heater leads on either side of the index pin (1 & 12), all the others go in the pins relative to that.
Here's a diagram of the 16GP4

http://www.google.com/url?sa=t&rct=j...1kHKgA&cad=rja

If a tube is electrostatically focused like the 7DP4 then it will have an extra wire, usually connected to one of the extra pins found on some base caps.
The 16GP4 is magnetically focused and won't have the extra wire.

When I look at the Cathode "K" inside the CRT I see four connections to it from the tube base. Two connections have leads on them. One is a long one, one is a short one. The other two don't have leads on them. I would have thought that there was a circuit through the two cathode leads but I guess not. I also think my sketch is wrong on one of the leads that I show going to G1 it's actually going to G2 which I can't see because it's inside the CRT too far. I'm guessing it's the lead on the left side of the sketch that I show going the the G1.

With all that said How does this sound. The two heater leads are cap pins 1 and 12. Pin 11 goes to the K, the long lead. Pin 2 goes to G1 and Pin 10 goes to G2. The two heater leads will position the cap. I think I'll strip some single wire old 24 guage telephone wire for the sheath and slide it down over the bare leads with the longest reaches, attach some guide wires and put the cap back on. I don't know if this CRT is any good but I will find out soon.

If I looked at the guns and bases of several of my CRTs, I might be able to see if there is a pattern/standard to them, since we have determined that the terminals do not connect straight through to the bases. On my 5AXP4, the two heater terminals are matched to their base pins, so your positioning plan sounds good.

crt
 

If you need a 16gp4 let me know, I can help you. I have a few very good ones.

I got the connector back on based on the arrangement we talked about and tested it Amazing after about three hours on the tester the emissions were up at mid scale on my BK. Thanks for the Help!

Excellent! I am happy to hear that it worked.

Opps. My 16" does have the switch too. I just missed it.

Post some pictures of your Porthole.
Its a lot of eye candy :-)

Carl

This has been my lucky week! I picked up another Zenith roundie from a guy in LA. It's a 50 Washington 24G26 (G3275RZ) . It has a 16EP4 CRT. When I first looked at the set I was sure the CRT was gone. It had a brightner on it. I tested it and the meter strated to climb. It didn't stop until it reached the highest good level I have ever seen on a used CRT. Almost 100% I couldn't believe my eyes. I double checked everything and sure enough the setting were correct. When I got it home I was able to rotate the CRT a bit and expose a lable that was under the support. The CRT is a rebuilt which explains why there were no identifying marks on the connector or the neck. I tested it again and it's definately as good as new. I think what happened from what the owner said is that the repairman didn't know what he was doing and possibly replaced the CRT then reattached the brightner from the previous weak tube thinking it was part of the set.

This afternoon I watched some old 1950's TV shows on my Zenith 24G26 Porthole.
These are neat Televisions.

How is the cabinet on your new acquisition?

Carl

My goal is to be so comfortable with my stock of 16" CRT that I never worry about a bad tube.. Can you imagine if I had to go out looking for one in the middle of an episode of lucy or Graucho. Especially the part when the little birdy comes down when they say the magic word..

"Say the Secret Woid and the duck will come down..."

I have not had the pleasure of watching my vintage sets yet. Lots going on. But I can see the light at the end of the tunnel.

And Carl... I have lots of DVDs of those characters that you like and post pictures on your set of ;) Believe me that when I finally restore my 12" Zenith Porthole, "George" will be catching grief from his wife...

Lonesome George on the Carson Show.

http://www.liketelevision.com/likete...ie&theme=guide

Even better

http://www.youtube.com/watch?v=AmYcO...eature=related

The cabinet was toast so I left it behind. The seller is going to relist it on CL and see if someone wants it.

Watching George Kingfish Stevens on a B&W TV is definitely fun. The series Amos N Andy is one of the best acted and scripted show especially by todays standards where the story writers seem to focus on effects and using the F-word. Several actors in the Amos N Andy show should have been awarded Oscars - especially the Kingfish.

Carl

I don't recall the George Goble show on TV ... like to see more episodes. I was 7 years old in 1955. Got into watching Johnny Carson in the early 1980's.

BTW, out of curiosity I purchased a DVD on Ebay of a failed TV Pilot "Let's Join Joanie" 1950 Joan Davis Comedy. Might be fun.

Carl

I've been on the look out for Zenith Portholes too. Love to find a 12" chassis that I can play with. After I restored my Porthole, I obtained a B&K Television Analyst and a Sencore VA62 analyst. Like to learn signal injection skill and learning more about TV circuitry.

Carl