[Jeffhs]

If the two tubes were of the same type, e. g. 23EGP22, I don't see why one could not interchange RCA and Zenith CRTs, although personally I'd replace a Zenith tube with an RCA for reasons outlined below.

I have both a Zenith and an RCA color TV. I have to say my 1999 RCA XL-100, with a dark-tint CRT, has a much better picture than my Zenith Sentry 2, which was new some eight years ago. The dark-tint CRTs in today's tube TVs, in my opinion, have much better pictures, especially in bright lighting conditions. The dark-tint CRTs (including Panasonic's PanaBlack series, Sony's famous Trinitron tubes, Zenith Chromacolor, et al.) produce much richer colors and blacker blacks (not to mention whiter whites) than the earlier tubes with dark gray faceplates. Also, today's color sets have many more and better designed color signal processing circuits than did sets of as recently as 15 years ago; they are completely automatic (as opposed to sets with so-called "auto-color" buttons on their front panels; these ordinarily only switched in preset color controls and were not true automatic color systems).

It's difficult to say, however, which tube lasts longest. The longevity of a CRT depends mainly upon how much the set is used. TVs which are used many hours a day or kept on from early morning to late night are more likely to require CRT replacement (not to mention repair service in general) in a relatively short period of time than sets which are generally only used during prime time.

Given the problems now being reported with Zenith sets (which are now manufactured by Gold Star), however, especially in the area of the CRT, I would have to say, if pressed for a quick answer, the RCA tubes are probably better in the longevity department. In this forum alone I have read of more problems with recent-vintage Zenith sets and their CRTs than I have read of the same problems with RCA sets. (It has been reported in this forum that the CRTs in Zenith sets of 1992 vintage to the present have the worst reliability record.)

The CRT in my RCA, however, after almost four years, still works as well as it did the day I bought the set. (I recently heard of one situation in which the CRT in an RCA TV of late-90s vintage failed after only two years, but this problem may have been due to a design flaw in the tube.)

RCA's ColorTrak system was, if memory serves, one of the first (if not in fact the first) completely automatic color control systems. It automatically balanced contrast and color adjustments to produce correct colors and color levels in the picture; I understand the ColorTrak system also used a photocell, located beneath the CRT, to adjust brightness and contrast according to room light conditions.

A variation of the original ColorTrak system is used in today's RCA tube TVs; the new system is no longer referred to by RCA as ColorTrak, but the automatic color circuitry works on the same principle (without the photocell). Modern RCA tube sets have not only automatic color control systems (defeatable via a menu option in the user control panel, accessed by means of the MENU button on the set or the same button on RCA remotes) but also circuitry which monitors (and corrects, if necessary) black levels, to keep blacks from washing out. These circuits are what RCA refers to as "black stretch" and "black lock" systems (at least that's how they are described in the advertising for my set). These three systems work together to produce a pleasing and accurate color picture; they are much better, IMO, than the first ColorTrak systems in RCA sets of 1970s vintage.

The ColorTrak system was preceded by what RCA called "AccuColor." The latter was simply a button which, when pressed, disabled the front-panel color and tint controls, while activating preset controls for color, tint and contrast (the latter were set at the factory, probably using color-bar test patterns rather than actual television programming, and are the defaults.)

Many other companies, among them Zenith, Admiral, etc. used the same type of preset color control system, although Zenith's "Color Sentry" was in fact a true automatic color control system. The company advertised this feature in its ads for its late '70s consoles by the phrase "think of it as a control room in your set." This was, I think, in direct competition with RCA's ColorTrak system of the same era.

The Zenith "Avanti" was a 25-inch color console in a white pedestal cabinet, with simulated rosewood on the top and sides. This model was introduced by Zenith in 1972; the original had the old-style detent VHF and continuous UHF tuners, but no remote. Yours looks like a slightly later model since it has several refinements the original Avanti did not have, such as Space Command remote control and Zoom, not to mention the vertical channel-selector window with continuously-variable tuning (via electronic varactor diode tuners, which were the first electronic tuning systems; they preceded today's quartz-synthesized cable-ready tuners) for each channel.

BTW, on the subject of quadraphonic sound, you may be right about the other poster possibly (even likely) referring to his system having an 8-track quad stereo tape deck (and, of course, being completely separate from his TV--we'll just have to wait until he posts the pictures of the system, I guess). There were several Zenith integrated stereo systems of early '70s vintage which incorporated 8-track tape systems, though many of them were straight stereo, not quad. I had such a system (with a stereo 8-track deck) for 17 years and liked it a lot (even played some 8-tracks on it, though I used the single cassette deck a lot more since most of my music was and still is on cassettes). When I moved four years ago, however, I gave it up and bought my present system, an Aiwa CX-NA888 AM/FM/cassette/CD 240-watt bookshelf stereo with 8-band graphic equalizer and surround sound. It sounds much better than my Zenith system ever did, but then again these modern systems, particularly the better ones such as Aiwa, Panasonic, et al, do generally sound much better than did even the best integrated systems of 20-25+ years ago. My Aiwa system will produce a simulated four-channel effect using four amplifiers, but with only two speakers (three-way--woofer, tweeter and a powered subwoofer in each enclosure). I don't know for the life of me how they do it, but the system sounds good to me, so what difference does it make as long as it works as it should?

Your friend had a very sophisticated Technics quad receiver. I remember those systems with the small oscilloscope on the front panel, which was used to balance the sound from each of the four speakers. The quad era was interesting while it lasted, but unfortunately it ended when the decade of the '70s did (though I have a feeling it was on its last legs already after 1975 or so).