Zenith F2-735W w/ 16F23 chassis

[heats00]

Well, I'm feeling a little stupid at the moment. A while back I posted looking for schematics for this Zenith, and I figured I could at least get the chassis pulled out and start cleaning while I wait for schematics to get here. Today I started by removing the tube socket for the picture tube, removed to the leads to the tuner and speaker, discharged and removed the high voltage lead, removed the power switch/volume control and removed the 4 bolts from underneath the chassis, thinking that everything should be loose for removal. There still seems to be something attached at the front of the chassis, but I can not see where it would be. Am I missing something obvious?

[jr_tech]

Pencil box?

jr

[DavGoodlin]

Originally Posted by jr_tech

Pencil box?

jr

There may be screws inside the controls compartment. I have a similar set but it worked as found and I didn't need to pull the chassis.

[zeno]

Top of CRT. See the 1/4" with the half moon washer ?
Should be 2 of them. The CRT will stay on the chassis
unless you unscrewed it.

73 Zeno

[heats00]

I found the half moon washers, removed all 4 of them and the whole set pulled out. Thanks Zeno.

Still quite a bit of dust underneath to deal with but I finally took a peak at the flyback and it looks pretty rough. Is this repairable or would I be better off sourcing a NOS one? I do not have a flyback tester, but this set did have full raster/snow before I pulled it apart.

[Electronic M]

The fly is fine if you saw it produce a raster. The wax/tar coatings on flys peel/crack off from age sometimes....It's no big deal. If it is arcing anywhere or you are worried about that then recoat it with wax or sensor safe RTV silicone. I've seen good looking flys dead, and scary looking flys work...Electricity don't care what it's path looks like as long as it has a path.

The only time to worry about a fly is when it has not produced HV for you and there is a LOT of melted wax (a few drops is normal in some sets) and possibly evidence of fire in the HV cage.

[heats00]

So, I've gotten this far. I've replaced all the electrolytics and all tubular caps, along with a few suspect resistors that were way out of spec. The yoke was crumbling and the rings were falling out but I was able to source a NOS Thoradson so I replaced that as well. I got everything back together and fired it up, to see this. I thought this was a good sign and hooked up a DVD being played though my old Playstation 2. I figured that I would have some adjustments to make due to the replacement yoke, one of which was a small rotation to square up the image, and a little adjustment to the rings. I am unsure however on how to get the picture to move up the screen. Is this another yoke adjustment or am I missing something entirely?

[tom.j.fla]

That is called neck shadow just push the yoke forward on the tube and you will get a full screen display. Seen that more times than care to count. All the best, Tom

[heats00]

Thanks Tom! I figured it was something easy.

[heats00]

I pushed the yoke up as far as it would go, including loosening up the yoke support and adjusting it as well, and I still have two small shadows in the upper corners. For whatever reason I am having troubles with getting the right adjustments. Just when I think it's all set and start watching, the scene will change and the picture will start vertically rolling with some slight horizontal deflection, but when I touch the vertical hold adjustment it seems to stop.

What is the proper way to go about making adjustments? Do I start with yoke adjustments, then centering rings, corrector magnets, AGC, vert linearity, vert size? Also, I seem to be missing the width control sleeve entirely, is it necessary?

My first television, happy to get a picture, frustrating to get it 'right'

[Electronic M]

You may want to adjust the centering rings on the yoke to see if you can get rid of the neck shadows.

There is no fixed order on the controls....Tackle one problem at a time.

[zeno]

The width sleeve ( actually hoz lin ) is often missing.
It was a cheat to get a little more width & not put
in another tube or troubleshoot a very minor width
problem. I know of no bad effects.

73 Zeno

[tom.j.fla]

One other thing, those wing like things are linearity magnets, move them away from the bell of the tube and see if that helps. The arms maybe brass but if not still will bend. So bend them and see if the picture fills the screen. All the best, Tom

[heats00]

Thanks for all the help. I was able to fiddle with all of the recommended adjustments, and was able to minimize the shadow, but it is not entirely eliminated. I think that I will be removing the chassis once more before to replace a few suspect resistors (for peace of mind) before I call I done, and will have to check how everything lines up with the yoke to see if there was any interference from something. I also wonder if the plastic of the replacement yoke has deformed.

[heats00]

After further research, I may have gotten the wrong yoke for this application. There are two parts #'s in the Zenith Service Manual. Zenith #95-1768 is called for in the 16F23 chassis parts list but a #95-1771 is called for with the Parts List based on TV Model F2735W. I was able to cross the #95-1768 to a Thordarson Y98 yoke that I purchased from Moyers, but now I am questioning if I have the right one. Does anyone know the difference between these 2 yokes? Is there a cross to a Thordarson # for the 95-1771?