Where to get picture tubes?

Bobby D: Is it you're thinking that the chassis was housed in some kind of case to make it portable and it plugged into a cigarette lighter for the 12v?

[jr_tech]

The 8AP4 has only a 54 degree deflection, which would reduce the amount of power required to produce a raster... perhaps that was a consideration in this mobile application.

The 8AP4 is 14.25 inches long, with a neck length of 7 inches... would that make sense with the distance that you have between the yoke and the front support?

jr

[earlyfilm]

Originally Posted by Bobby Dip

Thanks for all the excellent advice. You're right, I don't know for sure that it takes an 8AP4. (Maybe it's a 7".) But I do know that a 10" won't fit, I tried one. I like the idea of using a Test CRT. I will try to find one. . . . . . .

A fellow poster put some pictures of this set on Early Television Museum. I have also posted to Antique Radio.

http://www.earlytelevision.org/delco_car_tv.html
http://antiqueradios.com/forums/view...p?f=3&t=234225

Bob D.

Now, with the new info on ARF, all this now makes more sense!

I now understand why a metal tube would be used for a proof of performance, when they had no intention of ever making a production run. To reduce power consumption, they needed an obsolete narrow deflection CRT and these obsolete ones fit the bill off-the-shelf although an all glass CRT would have been preferred.

To test to see if an 8AP4 will fit mechanically, you don't need a dud. Simply make a paper template. To do this, go to:

http://frank.pocnet.net/sheets/127/8/8AP4.pdf

and save the PDF. Then print it, adjusting the scale until the inches on the drawing match your ruler. Cut same out and use that out for a trial fitting!

If you get an 8AP4, you will also need an bell rim insulator and then you will have to fabricate the top half of the mounting bracket.

Still your best bet is the 5AXP4 universal test tube which has almost the same degree deflection. Although the 8XP4 test tube is more nearly the original size, because of its 90 degree horizontal deflection, it would require modification of the H & V sweep circuits and you might possibly run into neck shadow (black circles on the edges of the image) problems, unless you change out the yoke, too.

Note: While the 5AXP4 (and 8XP4) filament draws 0.6 Amp (600 mills), there is no guarantee that other test tubes will do the same, as many seem to be unbranded rejects made for some other purpose. Your CRT must match the other 6v tube in series with the filament. The test tubes do not require an ion trap, while the 8AP4 does and that will be one less worry during the initial power up.

The five inch 53 degree test tubes usually sell between $10 and $50 on ePray, although I picked up mine for about $25 and that included shipping. I bought two, because my first one did not include all the cables, or the universal yoke, neither of which you need in your case.

Of the two types of power supplies, the dynamotor version is more reliable, but the vibrator ones are less expensive to manufacture.

This TV is going to pull more current than the same era 50 watt two-way radios used back then, and many owners of those quickly discovered that they had major problems keeping their battery charged.
Both types of power supplies are current hogs.

The dynamotor was a low voltage DC motor that turned a high voltage DC or AC generator. The DC generator was more efficient at delivering current at a different voltage, while the AC generator was more efficient, after rectification, at delivering higher voltage.

The vibrator was simply a normal auto radio vibrator on steroids! I've never worked on a TV with one, but have on both two-ways with tubes where they were twice as large and on mobile PA systems, not only were they large, but there were several of them.

Both of these power supplies are quite noisy, so they would be mounted in a remote location. To get an idea of what one might look like, see picture "C" on this link:

http://www.earlytelevision.org/tv_set_in_car.html

It is the separate chassis nearest to the man.

If you don't find one on ePray and can come up with a power supply and think you will be able to get this operational after recapping, I'd be willing to loan you one of mine for testing. Shoot me an eMail when your are ready testing.

James

[Electronic M]

Originally Posted by earlyfilm

Both of these power supplies are quite noisy, so they would be mounted in a remote location. To get an idea of what one might look like, see picture "C" on this link:

http://www.earlytelevision.org/tv_set_in_car.html

If you read the article in which picture "C" appears you would know that picture "C" shows the WHOLE TV CHASSIS not just the power supply....

[earlyfilm]

Yes, I could have worded the second sentence that you quoted better.

When viewing a fuzzy low resolution picture, the various elements are open to interpretation by the viewer. My interpretation is that there are at least two, and probably three, chassis are visible on the shock mounted platform in image "C". The chassis that the man is reaching for is not like anything in a normal period TV, so I assume that this chassis is the power supply. The power supply also could be in the cage visible in the trunk towards the front of the car, although I suspect that is the two way radio-phone mentioned as those were made commercially.

My intention here was to give an illustration of the size only, not to specifically what one looked like.

[Electronic M]

I gotcha.

Though from owning a Zenith porthole I can tell you that to me that pic looks to have good resolution and and looks like a single Zenith Porthole chassis. Those sets had a big chassis; the tuner alone, which was above chassis mounted, on most was the size of an AA5 table radio of the time add in an HV cage and power transformer to that, and there is no doubt in my mind that that whole thing is a standard porthole TV chassis (with some minor modifications obviously).

[earlyfilm]

Originally Posted by Electronic M

I gotcha. . . . . from owning a Zenith porthole . . . .

Electronic M,

Thanks! I stand corrected!

I am not familiar with the early Zeniths, as the town where I lived and worked, until I quit Radio/TV service in 1960, had no Zenith dealership until the mid-1950's. So I pulled up pictures of these chassis and hit this on the second try.

http://www.earlytelevision.org/pdf/Z...237-Riders.pdf

(Zenith chassis 22H20/23H22/24H20-21 in Riders Vol 8, Zenith page 6-8 left side)

If one looks at Figure 9 between pages 6-7 and 6-8 you will see a late 1940's Zenith chassis with a wired remote control sitting on top of a huge barrel tuner.

This is what I mistook for a dynamotor. An apparent shadow made it look like a separate chassis.

That is the beauty of this site. If someone royally puts his foot in his mouth, as I just did, someone will quickly correct him.

Since the Zenith's transformer is still in place, we must assume that he uses some source of AC, which in this home-made conversion probably would be a war-surplus dynamotor.

The smallest version of this set pulls 225 watts at 117 V AC.

I = P/E or 225 watts / 6 volts = 37.5 amps assuming that the dynamotor conversion was 100% efficient.

From memory, dynamotors were only between 60 & 70% efficient. On a quick search, I could not confirm this figure as these things are so obsolete.

Assuming 70% efficiency, the battery drain would be 54 amps!

In any case, this set would be a battery killer in a 6 volt car, and this illustrates some of the design choices in the Delco proof-of-concept set!

James.

[Bobby Dip]

Originally Posted by earlyfilm

To test to see if an 8AP4 will fit mechanically, you don't need a dud. Simply make a paper template. To do this, go to:

http://frank.pocnet.net/sheets/127/8/8AP4.pdf

and save the PDF. Then print it, adjusting the scale until the inches on the drawing match your ruler. Cut same out and use that out for a trial fitting!

James

Great idea James, here is the result:





So it's definitely a 54 deg 8 inch tube, with a "clip" type anode connector. Also, it's Mag focus and Mag deflection. Does this narrow it down to an 8AP4?

Bob D.

[jr_tech]

Does the yoke slide forward? Otherwise it looks as if the tube might be about an inch too short...

jr

[Bobby Dip]

Originally Posted by jr_tech

Does the yoke slide forward? Otherwise it looks as if the tube might be about an inch too short...

jr

Hi Jr, no the yoke does not slide. Actually the rim of the tube falls right into a slot. It's just hard to see from the angle the picture was taken. The fit is perfect. I just hope I can find a tube.

Bob D.

[Kevin Kuehn]

I think normally the yoke would slide up tighter against the bell of the tube.

[jr_tech]

Originally Posted by Kevin Kuehn

I think normally the yoke would slide up tighter against the bell of the tube.

My thoughts exactly... I think that I am seeing about an inch of neck out in front of the yoke that should be well inside the yoke. The center of deflection should be close to the middle of the yoke, not at the front edge, as shown.

I am stumped, as far as I know, no 9 inch options exist.

jr

[Eric H]

I would think there was originally a plastic insulator that would have filled the gap.

[Electronic M]

Originally Posted by Eric H

I would think there was originally a plastic insulator that would have filled the gap.

Not really. The metal part only goes from the face to the vertical line between the 27" radius and 54 degree markings from there back to the neck it is all glass and an insulator would be unneeded on that glass part. What gives that section away as glass is that section goes from straight conical to parabolic conical...That and I can't think of a CRT where the metal bell goes straight down to the neck...most metal cone CRTs dead end with something like a 4" diameter opening and then glass tapers down from there to the neck.

I don't think the 8AP4 is the correct type for this set unless the screen was quite recessed. I'd look at any P4 tubes in that general size range, then look for non-P4 types (if it was a prototype it might not have used a P4 screen), if nothing matches then I'd conclude it uses a custom CRT....At which point I'd grab the closest tube that can be had for a reasonable price and call it a day.

[Kevin Kuehn]

It's possible they were proposing to make a special CRT for this thing, but then it never happened. Personally I wouldn't be too worried about making it operational.