Where to get picture tubes?
 

I'm normally an antique radio guy, but I picked up an early 50's experimental car TV from what used to be Delco Radio. This is a one-of-a-kind set with no documentation, and is missing the picture tube. I would like to restore it to working condition, but there is no point going any farther until I procure a picture tube. There is no cabinet (some GM concept car was the cabinet!), but it looks like it must have taken an 8" round tube. I think the most likely candidate is a 8AP4. So where do you find these? No luck so far on eBay.

http://antiqueradios.com/gallery/mai...serialNumber=1

http://antiqueradios.com/gallery/mai...serialNumber=1

Bob D.

The 8AP4 is going to be hard to find I think.
There is a complete Arvin TV on eBay right now with one in it, kind of an expensive way to get a tube.

http://www.ebay.com/itm/Arvin-4080T-...item2ecb8d801e

I still think it looks like a 10BP4 would fit; I'd have to try one, since they are pretty easy to find.

I think it uses a 15GP22
:)

Bob,

I assume that this is the set pictured on ETF:

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

For a CRT, I'd buy one of the inexpensive universal test CRT's and use that until you get the thing working. I suspect that the set used a round glass 7 inch magnetic deflection tube, not the 8AP4 which was a metal bell CRT. The style of mounting bracket is rarely used for metal tubes.

First, I question it being made for a car.

I suspect that it was intended to be used as a field survey monitor and mounted inside the back end of a small panel truck and it could be used in remote areas where there was no AC available.

There appears to be a nameplate on the chassis. What does it say?

You also seem to be missing the complete power supply, which probably would be mounted on a different chassis. Unless you can find more information about the set, you probably will have to reverse engineer the set to build a power supply.


Test CRT's are discussed on:

http://videokarma.org/showthread.php?t=252335

You can find additional tube data here:

http://tubedata.tigahost.com/tubedat...37/5/5AXP4.pdf

http://tubedata.tigahost.com/tubedat...168/8/8XP4.pdf

James.

The tuner and some of the components are too new to be early 50's.
It's more like 1956 or newer. The yoke is a narrow deflection angle type.
I doubt they used a 7GP4 or an 8AP4, as they weren't that available, even then. The 10BP4, always seemed to be available, way into the late 60's.

Someone mentioned that it has a metal CRT style anode connector - Considering that this set could very well have still been in the developmental stages, it stands to reason that they may have been using a conbobulation of new and obsolete parts.

I cringed when I saw in the item description that the Arvin TV mentioned in this thread can be used with a Comcast (!) analog cable box. I mention this because I've read some rather disparaging comments in this forum regarding Comcast and its cable service, referring to the company as "Crapcast". Thank God I have Time Warner cable here. :yes: Not one bit of trouble with the service, although I do not use a cable box. The cable connects directly to the TV, so there is nothing much to go wrong at my end except problems with the physical cable line coming into my apartment, the cable going to the television, or the splitter that divides my cable signal between the TV, my computer, and my telephone (all three use the same cable, thus the need for a splitter).

A friend gave me a 10BP4 to try. The neck fits in the yoke, but it is too big-a-round for the front support. Even if I modified the front support, the 10BP4 would stick out way beyond the controls and make them inaccessible.

I might be willing to buy a complete set to obtain a 8AP4, if the price is right. What sets use an 8AP4?

Bob D.

The Arvin linked in the second post is about the only one and it is rarely found... there may also be some "house brands" that are actually the same set. Metal cone CRTs are also more likely to be "gassy" than all glass CRTs.
Take a good look at the pictures in the eBay link to the Arvin set... it clearly shows the metal cone of the CRT and the plastic insulator around the front of the tube to allow the metal cone to be connected to the HV supply.
It would be a shame (and expensive as well) to have to swipe the tube out of a clean working Arvin, but these don't turn up very often.

jr

I guess I stand corrected!
Evidently, they did use a 8AP4! After I looked at the entry at Early Television website, that specified an anode connector for a metal cone CRT.
I've seen many early TV sets, but didn't know an 8" metal cone CRT existed.
The only metal cabinet Arvins and Silvertones, I saw were 12" models. :scratch2:

That's Don's TV. There's a chance he has a spare 8AP4, so ask him if he would
sell one.

Bob,

I'd like to know how you determined this was an 8AP4.

That is one of the last CRT's I would have guessed.

If you look at the Arvin pictures you will see what a metal CRT anode collector looks like. Metal CRT's are prone to leakage with extreme temperature shifts like one would find in a car with the changing seasons.

Your picture on ETF showing the anode, looks to me like a universal anode post (like Dumont used) or cavity (like most others used) connector, that has the cavity part missing. (It has been 50+ years since I looked at one of these, but the two parts were usually held together with a screw.) In the late 1940's they were available as universal replacement parts, because some CRT's especially scopes, came with either gender connector.

It would help if you could post a larger image of the connector. Also, of the backside where the power comes in to this set. I do not see any thing that looks like a vibrator or a dynamotor and in the 1940's & early 1950's nothing else could generate HV from low voltage DC until the power transister came out.

I assume that you know that the metal anode will run at about 7,000 volts and requires an insulator between it and the metal chassis.

The bottom of the CRT strap looks to me like a strap for a glass CRT that is missing the felt or rubber pads.

Until you can prove the set is complete enough to restore, I'd still recommend that you stick to the inexpensive test tube.

James.

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.

You're also right that the set has no power supply. Evidently, this was on a separate chassis (probably using a vibrator). The set has a rather large gauge wire for 12V power that feeds the filaments. There is a connector for the remote power supply with 12V out and a single B+ line in. The B+ input goes directly to a filter cap rated at 300V, so I know B+ is less than or equal to 300V. I figure I'll be able to make a good guess at the B+ voltage after looking up a few of the tubes in my RCA manual. I have a Heathkit adjustable HV power supply to experiment with before I build a dedicated supply.

This project is going to be a real challenge with no documentation, and no guarantee that this set even worked when put into storage. (Also I don't have much experience with TVs, antique or otherwise.)

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.

The only 7" CRT I can think of is the 7DP4 and that was only used in the 1946 621TS as far as I know, it was also electrostatically focused so the Focus magnet wouldn't work with it.

The 8" Rectangular tubes of the mid 50's (8DP4) has a very short bell, your set obviously had a tube with a long bell. The 8AP4 is looking like the most likely suspect, out of date by the mid 50s but it would have still been readily available at that time.
It would be nice if you could get your hands on one (even a dud) and see if it fits.

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?

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. :scratch2:

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

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

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....

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.

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).

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.

Great idea James, here is the result:

http://antiqueradios.com/gallery/mai...serialNumber=1

http://antiqueradios.com/gallery/mai...serialNumber=1

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.

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.

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. :scratch2:

jr

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.

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.

I meant that the insulator would go around the face of the tube, like the Zenith Portholes that have the thick plastic spacer/insulator around the screen to keep the bezel from becoming electrified.
You can see one in this picture, it pushes the CRT backwards just about the right amount.

http://www.cerant.com/ZenithTV/MainChassis-top1.JPG

Sure looks like it has an adjustment for it. (circled in red)

Edit: Guess not, I see in other pictures on the ETF site that the adjustment on top of the yoke would prevent this slotted adjustment from being used. Or is the metal plate under the wing nut also slotted? If so, then the yoke should be slide-able.

Hi WISCOJIM, I looked closely and found that the slotted adjustment only moves the magnet assembly, not the deflection coils. I assume moving the magnets focuses the picture, is that correct?

Bob D.