Picked up an Airline 7"

[Eric H]

The Trapezoid one that's basically the same as a Sentinel.
Got it for $30, it's basically all there except a mouse has eaten half the Tolex off the cabinet, figured it might have a good 7JP4 at least and it does have all the knobs which are often missing on the Sentinels.

There always seems to be something to spoil the fun however and when I got it home I was happy to see a replacement Sylvania jug installed, maybe it will be good!

Well it is good all right, but it's also a 7JP7 with Blue Phosphor.

Oh well, I got $30 worth from the knobs and tubes, she also gave me a small box of tubes, nothing too interesting except one metal 6L6, looks like it might have another glass 6L6 in the HV oscillator socket. I did not get the radio in the picture.

[jr_tech]

How are you lighting up the tube? Does the Airline *actually* power up and produce HV & sweep?
The worst part about the P-7 phosphor is the long persistence yellow layer of phosphor, that produces a really smeary TV picture. Filter out the yellow with a blue filter and the picture is not awful to watch.
jr

[Eric H]

I powered it up with a working Motorola VT-71.
I suspected something was funny when I was removing the tube from the set, it has a very yellowish screen and that's why I suspected it might not be a P4 tube.

Are the phosphors in layers? I ask because the light seen from the back of the screen is much more blue than what is displayed on the face.

[jr_tech]

Originally Posted by Eric H

Are the phosphors in layers? I ask because the light seen from the back of the screen is much more blue than what is displayed on the face.

Yes. I believe that the screen was deposited in two layers. The viewing side yellow Cadmium Sulfide (silver doped) first then the beam side blue Zinc Sulfide (silver and zinc doped). Perhaps later a one part "coated" phosphor was developed, I don't know.
jr

[EdKozk2]

I used to use a 5UP7 for slow scan TV in high school along with a PMT 931a tube. You never know who may need an old 7JP7.
Ed

[ChrisW6ATV]

I think a cool display would be three matching restored VT-71s, one each with a 7JP1, 7JP4, and 7JP7. (Are there any others? Maybe four sets in a row.) All showing the same video. Eric, hold on to that tube!

[decojoe67]

Too bad the Airline is in rough shape. It may be worth the time to completely restore it. I've heard by some collectors that replacing Tolex is sometimes surprisingly easy. The round screen versions of these trapezoid portables are the most interesting by far and come up much less often than the typical Sentinals.

[electronjohn]

I think Parts Express has Tolex by the yard used in restoring vintage guitar amps. Maybe they have the right shade...or close?

[47'Plymouth]

That set was made at the TELETONE TV factory for Airline
It's a cookie cutter chassis from surplus military parts
They made for Firestone,Sears Silvertone,Montgomery Ward
And Sentienal