Hawes Mechanical Television Archive by James T. Hawes, AA9DT
Choose a Host TV for Col-R-Tel®

Consider Bandwidth

What TV Type? Collectors want to know the best type TV set for Col-R-Tel conversion. I can't really specify models. I've seen Dave Johnson's demonstration with a DuMont set. Cliff Benham has used a Pilot 12-inch set. He is now converting a Philco 12-inch set. The Pilot required a jumper across the sound trap. The jumper increased video bandwidth, and allowed Col-R-Tel to find burst and chroma.

The best sets come from years before 1954. After the arrival of color sets, the industry narrowed the IF bandwidth in some monochrome sets. Sets with narrower IFs didn't display interference from the lower color I and Q sidebands. A narrow bandwidth TV might not give Col-R-Tel enough signal to work with. Col-R-Tel needs the high frequencies. Let's be specific here. The frequencies I'm talking about range from 3 MHz to 4 MHz. The most important of these range from about 3.08 to 3.28 MHz.

Illustration of 
       Col-R-Tel color wheel on top of vintage, black-and-white TV

By moving the Col-R-Tel inputs, you might make a narrow-IF set work. The signal takeoff point doesn't have to be at the CRT. For instance, you could acquire chroma and burst just after the video detector. Also, you can add a bandpass amplifier with a curve opposite to the IF. Colordaptor and Spectrac converters include such an amplifier. This amp reverses the attenuation and permits the converter to find the chroma and burst. I've just uploaded a schematic for such an amplifier to my Col-R-Tel Enhancements page.

Consider the Picture Tube

The maximum TV picture size is about 14 inches. The Col-R-Tel disc can't convert larger screens. Instead, Col-R-Tel comes with a size box that reduces the video image to 14 inches. Yet screen size reduction with the Col-R-Tel size box is risky. (Isn't everything that's fun a little risky?) The size box doesn't work well with all sets. Even the Col-R-Tel manual indicates that you might need to experimet with the wiring. My guess is that low-current yokes would function better than high-current yokes would. No sense in overheating an antique coil! I'd guess that the low-current types tend to be series-wound yokes. Take care. Check the yoke and size box for excess heat. Some CRTs use a series-wound vertical coil and a parallel-wound horizontal coil.

Deflection type. The size box presumes electromagnetic deflection, rather than electrostatic deflection. Electrostatic sets aren't completely out, though. Most electrostatic sets have small screens. If the CRT face is small enough, you don't need the size box. In that case, deflection type doesn't matter.

Tube brightness is also a factor. Col-R-Tel and other converters seriously dim the picture. For this reason, some collectors swear by aluminized screens. Some electrostatic sets are very dim. Such sets require a different filter type than brighter, electromagnetic sets use. An electrostatic filter set passes more light. A bright set would wash out the colors. For a dim set, though, the special filters work surprisingly well.

Consider The Electronics

TV electronics. Besides deflection type, consider another electronic issue: Whether your set uses tubes or transistors. Color Converter, Inc. designed Col-R-Tel for tube TV electronics. I don't know what effect Col-R-Tel would have on transistor TV electronics. Such an experiment probably isn't a good gamble. Steer clear of transistor sets.

Consider The Cabinet

Cabinet style. Cabinet style is very important. Obviously, projection sets are out. Your candidate TV might have a rounded top. The Philco 48-1001 is such a set. (See my links, below.) On some round-tops, mounting the disc would be difficult. Still, you might be able to shim up the disc mount. Some sets include doors that might get in the way of the disc.

If the cabinet has a raised center portion, you might have to build a support for the disc. For instance, such is the case with the Andrea model 1-F-5. Otherwise, this set might be a good bet. Many sets with small picture tubes will probably work, but you'll have to build a platform to bear the disc. Certainly a platform would be appropriate for a "scope set." Scope sets are tabletop units with tall, narrow cabinets that resemble oscilloscope cases. Sentinel, Tele-Tone and others made scope sets.

Where are the TV controls? TV control position is important. In front of the TV, the Col-R-Tel disc takes up a lot of space. Viewers watch the TV image at the lower-right corner of the Col-R-Tel disc. The viewing window is at roughly five o'clock. On some TVs, the disc might block the TV controls. Maybe you should consider a TV model with side-mounted controls.

At least, look for a TV with the picture tube on the left. Ideally, the controls should be on the right. Some suitable sets might have controls well below the picture area. The controls must clear the bottom of the disc enclosure.

Pilot® Models

Col-R-Tel expert Cliff Benham prefers some Pilot models. Here is an edited version of Cliff's Pilot set description. Cliff used the Pilot with his original Col-R-Tel installation in 1960...

    The Pilot model TV-125 is a 12-inch set with a 12LP4 CRT. Judging by the CRT size, the manufacturing date must be at least 1948.
    The Pilot is in a mahogany wood case. The CRT is on the left and the controls are on the right. The set has a vertically mounted chassis of thick aluminum! Inside the case are three continuous tuners using tuning condensers[!]. A nylon dial cord and a band switch control all the tuners. The front panel switch selected which of the three condensers feed the IF. The tuners cover Channels 2-6, FM 88-108, and Channels 7-13. With a switch on the front panel, you select which of the three bands you want. Then you tune the set like a radio. The set lends itself very well to supporting Col-R-Tel.
    A 1952 Sams index only mentions the set. That index claims that the set might appear in a later Photofact folder. Sams never published the Pilot TV-125 folder. I have never found a schematic for the Pilot. Still, judging from the tube lineup, the Pilot is similar to RCA 12-inch sets of the same vintage: Except for the tuner! Also, the Pilot is unique, in that it has an aluminum chassis.

Classic Sets That Might Host Col-R-Tel

Other sets that might support Col-R-Tel. Here are some sets that might be good choices for Col-R-Tel installation. I've located many of these sets in Morgan McMahon's A Flick of the Switch...

  • Admiral 12X12: A 1950 tabletop set with controls well below the CRT

  • Admiral 19A11S1: 6-inch CRT

  • Motorola 10VT3: 10-inch CRT

  • Motorola 12VK18: 12-inch CRT; knobs on bottom

  • Philco 49-1002: Left-side CRT; flat top; see links below

Photo links. Here are some sites with TV restoration photos. See the models that I list below...

Value of the Restored Set

A note about value. After you recap the Col-R-Tel, install it and get everything working, what's the set worth?

Harry Poster. Harry Poster's 1994 price guide lists a complete model 100-1 at $600. The color wheel alone is worth $400. Other kits or homemade wheels are only worth $75. Harry Poster collects and deals in vintage television sets. Apparently, his commercial interest isn't restoration. Instead, he rebuilds sets for TV, radio and advertising purposes. He also authors and publishes appraisal books. His Web site offers free appraisals. You can't beat that price. Harry's definitely the one to contact. Click... Harry Poster

Audiokarma. At the Audiokarma forum, I read that one Col-R-Tel set sold on eBay for $4,000. To my way of thinking, that's a very inflated price. I can't believe that all such sets are worth anywhere near that amount. Maybe the unit was exceptional in some way. I've seen other eBay Col-R-Tel auctions that closed in the low hundreds of dollars. These lower prices are more in line with the Poster book. By the way, here's the link to the Audiokarma Col-R-Tel pages.

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