Purchased on the bay. Cosmetically okay, but I think I'm going to refinish the cabinet.

The chassis is a piece of cake. Its in nice shape, all the tubes test fine, and it actually has horizontal sweep. I've already recapped it, save for 6 electrolytics, plus those two .005 5000V caps.

I'm rather impressed with this little 7 inch television. Nice build quality, and a very simple, serviceable little chassis.

Outside of the need to refinish the cabinet, which means decals, I shouldn't have much problem with it.

It came complete, with all the covers etc, but it didn't come with knobs. That may be a problem.

Anyways, I'm away from my camera and computer for a few days, but I will post pictures when I return. I like this TV.

Lee:smoke:

Oops. My bad. It's TV7W.

W as in Mahogany. :smoke:

I think they went with "M" for the metal version and "W" for the wood. I'll be starting work on mine soon.

The logo decal is red and gold. Not sure it two color decals are and more difficult to have made.

I've done a recap, in the only caps left to be replaced are the 4 canned electrolytic caps, and the two .005 5kV tubulars.

the tv works, but does not have vertical deflection. I've tested c81 and it is shot. No surprises there.

I've ordered 6kV replacements from Justradios. I assume they will be much more durable then the old wax paper caps. I almost ordered the 15 kV caps, but I figured that was overkill.:smoke:

I tested all those one Watt 1 mega ohm and above resistors on the back panel. They all seem to test 10 to 20 percent above spec. A few seen below spec.

How critical are they? Should I just replace them all with modern two-watt gray resistors?:smoke:

I suspect if they're all drifted up about the same, you'll be OK because the voltage divider ratios will be about the same.

Not seeing much in the 1+ watt megaohm value range at Mouser :(

The reason they used 1 watt is because they have a higher breakdown voltage than 1/2 watt resistors. They strung a bunch in series for the same reason.

Typical limit for 1/2 watt is 350, 1 watt 500 and 2 watt 750 volts.

I purchased from Just Radios a complete kit of 2 W resistors. Many are valued 1 meg and above.

I'm just curious as to whether I should shotgun all these one watt resistors, as they are 65 years old, and may not stand up.:smoke:

Good deal. I guess the mainstream distributors don't see much demand for the high valued resistors.

As for replacing them, I've yet to see one fail, but they get far off value, it will effect the image on the CRT.

Here's a few pics of the chassis. Before shots.

It's been recapped now, and I'm waiting on .005 6kV caps.

National was an "Old Line" mfgr of ham & SW radio goods, they knew their way around electronic stuff.

Yup. I'm pretty impressed with this little TV.

This version uses 12 volt vacuum tubes in the horizontal and vertical sweep and synch sections.

I have the cabinet clamped straight to try to eliminate warpage. That part of this TV I'm not so impressed with, as it has little reinforcements internally. Oh, well. I'm in no rush.:smoke:

Here's a shot of the chassis circuitry. Note the transformer next to L33, the filter choke.

It doesn't appear in the Rider's manual. I wonder what it is?:smoke:

Mine has it too. I'm pretty sure it's the auto-transformer used for the 105-115 / 115-130 AC line range selector shown on the first page in Riders.

https://c2.staticflickr.com/4/3803/12941282304_b16f2e3634_z.jpg (http://www.flickr.com/photos/70039806@N00/12941282304/)

completely recapped it. Restored full vertical deflection. Now I'm going through all the brightness, contrast, etc. Controls. Cleaning all contacts, disassembling them when necessary.:smoke:

The TV-7W is up and running nicely. Many thanks to kbmuri. As always, his help is invaluable.

I bypassed the tuner, running the dvd signal direct to audio & video for a nice, clean signal.

Pics later.:smoke:

completely recapped it. Restored full vertical deflection. No I'm going through all the brightness, contrast, etc. Controls. Cleaning all contacts, disassembling them when necessary.:smoke:

Those Nationals look about the most like lab test equipment when it comes to how they're put together. :thmbsp:Very nice stuff - like to see the operating pics

Here's the chassis, finished and working. "The Music Man" (1962)

Very nice work, Lee.

A semi-final restoration note:

I had not replaced the selenium rectifier with a diode. So, I went down to the local Radio Shack to find a 1N-4007 (1000V 3 amp) but all I could find was a 1N-4005 (600V 1amp).

Installed it anyways, and noticed the HV is now over 3KV, the screen is brighter and clearer, and the Audio screams loud and clear with no distortion.

I figure the 1N-4005 might be still choking off the HV (should be over 4KV), so I will replace it with a proper 1N-4007 when I get one.

Replacement electronic parts on Martha's Vineyard ain't all it's cranked up to be.:smoke:

I'm thinkin' that Bad Boi was made not too far away in Malden, Mass...

You are correct, BD. Malden, Mass.

I'm betting once I put the correct diode in this TV will finally be uncorked. :smoke:

What do you watch on a 1948 National TV 7w?

Why, Humphrey Bogart, of course. In the Treasure of the Sierra Madre.:smoke:

I'm betting once I put the correct diode in this TV will finally be uncorked. :smoke:

Hmm. I'm thinking all silicon diodes have basically the same forward voltage drop. Their voltage rating(peak inverse voltage)is the max reverse voltage they can block without breaking down (self destructing). So I don't believed changing from a 1N4005 to 1N4007 is going to give you any higher output voltages. The 1N4007's higher PIV will give the diode's a higher margin of safe operation.

Nice job on the restoration. Nice sharp picture. :thmbsp:

Hmm. I'm thinking all silicon diodes have basically the same forward voltage drop. Their voltage rating(peak inverse voltage)is the max reverse voltage they can block without breaking down (self destructing). So I don't believed changing from a 1N4005 to 1N4007 is going to give you any higher output voltages. The 1N4007's higher PIV will give the diode's a higher margin of safe operation.

Nice job on the restoration. Nice sharp picture. :thmbsp:

Thank you. I've been running it for 3 days now, about 4 hours constant usage in one setting. The only nits to pick is an occasional sonic crackle, or a rare horizontal tic. But 99.5% of the time she is a rock-solid performer. In a room with moderate light the picture quality is very good. Great in the dark.

The sound quality is superb.Even out of the cabinet it has decent bass. Mid and treble is excellent. All told, this is one impressive 7" television.

If the diode (rated 1 amp) isn't holding it back, I wonder what is causing the lack of hv.I've replaced all caps, and I mean ALL caps, in the hv, horizontal, and vertical sections, along with all resistors that were off by more than 10%. All the resistors at 1 meg and above are replaced.

It also has a slight vertical linearity issue. I figure this is also due to the lack of peak hv. I get only 3.5 kv at a test point that should yield 4.5.

I have tuned the mica in the hv cage for peak voltage. :smoke:

All the bleeder resistors and all the resistors under the hv cage were replaced. :smoke:

Not sure about your low high voltage. 1N4005 and 1N4007 are both rated for 1 amp current.

Not sure about your low high voltage. 1N4005 and 1N4007 are both rated for 1 amp current.

My error. I thought 4007s were 3 amp rated. Then the diode clearly is not the bottleneck. :smoke:

Soooo...that leaves the flyback. I already cleaned it with alcohol and blew dried it with a heat gun to chase away any dust, moisture, etc.

I've read these pages on electrostatic 7" tvs...:smoke:

Alright. Guess tonight's movie...:smoke:

Flight of the Phoenix?

ONE OF MY FAVORITES!!!!!!

"I told you there would be no difficulty in building this aeroplane. I also told you it would require an outstanding pilot to fly it. The only thing outstanding about you, Mr. Towns, IS YOUR STUPIDITY!!!!!!!"

Correct. Very good!:smoke:

ONE OF MY FAVORITES!!!!!!

"I told you there would be no difficulty in building this aeroplane. I also told you it would require an outstanding pilot to fly it. The only thing outstanding about you, Mr. Towns, IS YOUR STUPIDITY!!!!!!!"

"Ahhh..Lou..."

Flight of the Phoenix? :thmbsp:

"Oh, I thought it was all cut and dried...you mean you have a few little things you haven't figured out yet, huh?"

"Oh, I thought it was all cut and dried...you mean you have a few little things you haven't figured out yet, huh?"

:thmbsp:

Did you remove high voltage cage and change out the .1 capacitor C50 and check the resisters R61 And R62 in there. These are sometimes overlooked.

"Oh, I thought it was all cut and dried...you mean you have a few little things you haven't figured out yet, huh?"

Did you remove high voltage cage and change out the .1 capacitor C50 and check the resisters R61 And R62 in there. These are sometimes overlooked.

Yes. I pulled the cage and replaced EVERYTHING underneath, except the variable mica cap.:smoke:

https://www.youtube.com/watch?v=V0hIoLNecqI

As a matter of routine I replace 1/2 watt resistors with 1 watt, and 1 watt with 2 watt.:smoke:

https://www.youtube.com/watch?v=V0hIoLNecqI

When I was a 10 year old kid, I used to design and build my own flying model airplanes. Obviously, "The Flight of the Phoenix" was one of my favorites. Still is.:smoke:

When I was a 10 year old kid, I used to design and build my own flying model airplanes. Obviously, "The Flight of the Phoenix" was one of my favorites. Still is.:smoke:

I built two. The first was one of the ones that was attached to the string. So you started it up and you swung it around in a circle. Second one was a complete RC model. Loved them both.

Now that she's burned in for about 10 hours total, I noticed the HV has climbed slightly past 4kv. Also the crackling sound is now limited to a brief time (3-4 seconds) on start up. No more tics.

I'm going to call this one done, barring any relapses. But since I've replaced all the caps except a handful of micas in the sound and IF stages, I don't anticipate that.:smoke:

The HV improvement and reduced "tics" do point to possible slight flyback moisture or similar issues, don't they?

The HV improvement and reduced "tics" do point to possible slight flyback moisture or similar issues, don't they?

Yep. Thought the same thing. It's about the only thing I didn't replace.

Been watching it further, and now she has barely any tics on warm up. She's fine.:smoke:

Don't want to nit pick, but this is an electrostatic set so shouldn't it have an HV coil rather than a flyback.

It does have an RF-type HV supply, but those coils seem susceptible to moisture. Some people bake them in an effort to drive out moisture and squeeze out more HV.

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

Don't want to nit pick, but this is an electrostatic set so shouldn't it have an HV coil rather than a flyback.

A good nit to pick. We should call it what it is.

By cleaning it with alcohol, followed by a blow dryer and burn in, the HV is back to normal.

Hi Phil. You going to ETF?:smoke:

Um, probably. We have a remodeling project (endlessly) underway and there is a constant stream of surprises & questions.

Phil Nelson

Oh, I know what you're going through. The family has made me point man on the summer home renovation.

Fortunately I'm just coordinating it all. Two work crews are doing the actual labor. But they are maistros. Their work is superb.

When they're done, I'm going to pick out one of the rooms as a lab for tv restoration. :smoke: