I left the ceramic doorknob type caps for the horizontal alone, but restuffed the vertical with new ASC high voltage caps.
https://farm8.staticflickr.com/7574/...14dd57c0_c.jpg

A few of the resistors in the high voltage divider change were out of tolerance and replaced.
https://farm6.staticflickr.com/5613/...d4e0ee77_c.jpg

I went with NOS for now, but have some modern high voltage resistors ready if they don't work out.
https://farm8.staticflickr.com/7565/...5758a18b_c.jpg

https://farm8.staticflickr.com/7549/...d2fdb41b_c.jpg

The brightness and all three high voltage pots were frozen and had to be taken apart. All you need to do is carefully pry up a bit of metal and the back covers come right off. I used electrical parts degrease to clean out the old lubricant. Isopropyl alcohol works well too. After cleaning, I used white lithium grease.
https://farm9.staticflickr.com/8113/...18547db4_c.jpg


Here it is all recapped and ready for a first power up :)
https://farm9.staticflickr.com/8599/...f70a8fdf_c.jpg

Didn't National make the metal-bodied set w/a big "Power" meter on the side, that was sposed to show power of the video signal ?

Yes. It wasn't really a "TV set", but a test instrument for installing and pointing antennas. A field strength meter with a built in picture monitor. :smoke:

First power up was a partial success in that I got a picture but no sound.
https://farm8.staticflickr.com/7569/...c15f715d_c.jpg

Further investigation revealed a cracked 6AT6 that had gone gassy but still had filament continuity.
https://farm8.staticflickr.com/7491/...d7988529_c.jpg

Picture was still a bit dim and weak though. Bypassing the old selenium rectifier helped a bit.
https://farm9.staticflickr.com/8606/...e36d9e1e_z.jpg https://farm8.staticflickr.com/7523/...cf72e290_z.jpg

Eventually, I tracked down a bigger issue - an open peaking coil. Luckily, a little soldering touch up on one end restored continuity.

That improved the picture quality and brings me to what I hope is the final issue - poor horizontal stability.
https://farm8.staticflickr.com/7482/...ac8d6e33_z.jpg https://farm8.staticflickr.com/7556/...7fb1845e_z.jpg

I think this series of images taken while using a 7VP1 test CRT illustrates the problems.

Adjusted for a good picture.
https://farm8.staticflickr.com/7533/...6db89793_z.jpg

A short while later tearing appears. Tweaking the horizontal hold will get rid of it for a little while.
https://farm8.staticflickr.com/7559/...36ff2e54_z.jpg

A bigger issue occurs when there are large areas of bright and dark. Seems like the video is causing a horizontal offset. This set does have DC restoration that uses an average of the video signal as a grid bias. Seems like that might be leaking in to the horizontal circuit somehow ? Tough to track down since it's not always a problem.
https://farm8.staticflickr.com/7499/...55b4f614_z.jpg

Check out the 800v micas and resistors in the Hor Sweep & Synch circuits.

I replaced a bunch of resistors and the micas in mine. Pic is rock steady.

The step up transformer in the HV cage will take a while to "cook" to eliminate any moisture in it. HV will climb after that. Weak selenium rectifiers held mine back. OK after replaced by diode.

When you get audio back, be prepared for a loud sounding TV. They really crank.:smoke:

Thanks for the input. I ended up replacing every resistor, capacitor and tubes in the sync and sweep circuits and it made no difference so I'm calling it done for now. Didn't notice any issue with the HV coil. Maybe because it's winter and the humidity is low ?

I'm expecting to get the metal cabinet version sometime in the next few months and will compare the performance.

https://farm8.staticflickr.com/7526/...8e140b27_c.jpg

Ah. Sorry 'bout that. These NT-7s are so simple I was sure that would cure it.

Tell you the truth, I pretty much shotgunned most of the resistors, along with ALL of the caps in mine. All the resistors on the bleeder board I replaced with 2Watters. It plays real well, aside from a slightly squished picture bottom.

My cabinet, a mahogany one, is pretty beat. Finish all faded, decals pretty miserable looking, although the "National" logo I could probably resuscitate.

I'm thinking of coming up with gold decals from a vendor that's a close/exact match, font-wise.

Good Luck with Yours;

Lee:smoke:

My decals are in fair condition with the worst area being around the channel selector. I spruced up the cabinet with a light sanding and a few fresh coats of lacquer then a rub out.
https://farm8.staticflickr.com/7445/...230a8d3c_c.jpg036

I finally got the set all back together :) The horizontal sync seems a bit more stable receiving an over the air broadcast from a Blonder Tongue modulator which makes me think I was overdriving it on the workbench with my test signals.

That just leaves finding a few more of the correct knobs...

https://farm8.staticflickr.com/7408/...d4edb3be_c.jpg

https://farm8.staticflickr.com/7322/...69b269eb_c.jpg

Nice,
Great work as always. love that antenna.

Nice work Bob. You really get an early set playing like new. Great seeing these more obscure TV's working.

I got the same antenna... those work pretty well :D

SR

Beautiful job! That National and the Admirals are my favorite 7-inch sets.

I haven't redone the cabinet on mine yet. It's presentable, but weathered.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Looks really good!

That's one of the sharpest focus pictures I've seen on a 7" electrostatic, in recent memory! Good job.