1951 Zenith 16" Porthole

[Radiotronman]

Like many guys, I like to restore more than one set at a time. A friend of mine found this same cabinet in blonde with no chassis. It's near mint and the seller wants to get rid of it so a deal is being made to acquire it. I thought what am I going to do with it? Put the chassis in my mahogany set into the blonde cabinet since it's worth more? Then a few days went by and I found another seller wanting to sell his zenith chassis from a trashed cabinet. So now I'm trying to get a deal on that chassis so I have two complete sets. In the mean time I'm going to go ahead and restore the chassis I have. I'll order parts for my RCA portable I'm working on to save money on shipping by ordering all of the parts together. The chassis is 24H20 with a 16" metal tube, 16GP4 I believe. Like my other 16" I restored, the tube tests bad, but still lights up with a very watchable brightness to it. It also has the seperate power supply chassis. I'll irder all of the parts in the next week or two and get at it.

[Radiotronman]

Here is a picture with the doors closed. I like the more modern look to this over my other set which is more traditional. It also has very nice piano hinges down both full length doors and thick wood slats in the speak area. This set had many scratches, but good enough not to refinish. Maybe I'll use Howards restore a finish or just som red stain. The thread on how to display your sets has inspired me as I finish my basement in the next year. I decided I'd like to display and have working my better sets, like this one. If I can't make a deal on the chassis, because the seller is deciding on keeping it it not, then I may display it in the blonde cabinet.

[Radiotronman]

Here is the chassis with the 16" metal coned CRT. I've got a few portholes now, but still yet to come across a 19" porthole.

[Radiotronman]

Here is the underside of the chassis. I replaced a few of the capacities that I had. It looks pretty much untouched. It's amazing how much lighter this chassis is with a metal coned CRT. But I think they made up for it on the cabinet, as it's super heavy and every piece of wood on it is an inch thick.

[dieseljeep]

Originally Posted by Radiotronman

Here is the chassis with the 16" metal coned CRT. I've got a few portholes now, but still yet to come across a 19" porthole.

The set uses the old 52 degree 16EP4, not the newer 16GP4 70 degree CRT.

[John Marinello]

Originally Posted by dieseljeep

The set uses the old 52 degree 16EP4, not the newer 16GP4 70 degree CRT.

Wrong, x2.

24H20 chassis use the 16GP4.

The 16EP4 is a 60 degree tube.

[Radiotronman]

The picture us a little dim, but if you look on the upper right hand if my cabinet tube layout, it lists the 16GP4 for both 24H20 and 24H21 chassis. The schematic for this set (SAMs 120-13) also list it for the 16GP4.

[dieseljeep]

Originally Posted by John Marinello

Wrong, x2.

24H20 chassis use the 16GP4.

The 16EP4 is a 60 degree tube.

If I'm going to be wrong, I do a good job of it!
I looked at the Riders #6 coverage for that chassis and it looks like it was the last run of the portholes. They did have to switch to a 70 degree sweep to incorporate the 16 and 19" CRT.

[bandersen]

Ion trap magnet could be weak or flipped around backwards.

[Electronic M]

Part of me wonders if the door knob cap might be open.

[Radiotronman]

I've tried multiple ion traps and flipped them around and no change. Could it be a bad door knob cap? I've never seen a bad one.

[Electronic M]

I've heard of them shorting, but can't recall an open one. To me it looks like either the gun drive or the HV is varying across each horizontal line (which could be caused by an open door knob)...That or it is an electron optics problem, but you've checked the trap, and there does not seem to be a focus coil IIRC, so varying voltages seem more plausible.

[Electronic M]

If the set is focused properly currently and moving the coil does nothing, I'd like to know if adjusting the focus control away from proper focus changes how much of the picture is dark.

[Radiotronman]

Adjusting the set out of focus made the picture less sharp, as expected it would. But didn't do anything to help brighten the left side of the screen.

[Radiotronman]

It's got obvious sync issues that I'll have to solve, but what is strange, is if I turn the volume all of the way down, the left side of the screen will get brighter, further over and the sync will somewhat stabilize. Any thoughts?