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Originally Posted by Bobby Dip
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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