View Full Version : Need on-site help with Zenith round tube

06-11-2017, 01:40 PM
Fired up my Zenith round tube TV today for the first time. Got somewhat of a picture but don't know how to adjust it to make it bring in a real picture. Is there anyone in the greater Kansas City area or vicinity that's knowledgeable about vintage tube TV's that could help us with this? At this point we're beyond our level of knowledge. All caps and the high value resistors have been replaced. All tubes tested multiple times. Everything lubed and cleaned.

06-11-2017, 02:55 PM
Looks like the horz osc is way off freq.
Did it work before ?
On newer sets that use a coil for horz hold kids often
kept turning it WAY out of range.
Check your work in the hoz osc & swap the osc tube even if it checks good.

73 Zeno:smoke:

06-11-2017, 04:33 PM
No, we just finished resto. Never worked. Will note your suggestions and work on those. Thanks for the reply!

06-13-2017, 12:36 PM
It could also be that the video signal has a large high frequency oscillation on it.

06-13-2017, 10:48 PM
I agree with Zeno. The horizontal oscillator is so far off frequency it isn't funny, and yes, this can be caused by kids messing around with the oscillator coil. Turn the slug back into the coil until the picture comes back. As you adjust the slug, the number of horizontal strips will slowly decrease until the oscillator is on the correct frequency (15,750 Hz) and the picture is normal. It wouldn't hurt to replace the HO tube while you're at it, although if the set makes a good picture once the oscillator is set properly, a new tube isn't absolutely necessary.

BTW, your Zenith TV is one of the early 1950s "porthole" sets. (VK member John Marinello's avatar is one of these, "The Byron" from about 1951.) Get yours working well and it will serve you well, with a DTV converter box or cable box, for many years to come (don't try to connect an antenna directly to the TV's VHF antenna terminals--it won't damage the set, but you'll get absolutely nothing but snow on the raster and white noise in the sound, since all TV is digital these days, except for some cities which may still have one or two analog stations). Zenith was one of the best TVs made in the 1950s through about the '80s, second, IMHO, only to Magnavox and Andrea, the last being a now long defunct New York City-based TV manufacturer of the late '40s through the fifties.

Zenith's slogan was "the quality goes in before the name goes on", which was true of their TVs from the '50s until the Gold Star era, which began in the late '80s.

The last few years of the decade of the 1980s were, unfortunately, the beginning of the end for once-proud Zenith. The quality of Zenith electronics (radios and stereo gear as well as televisions) took a heck of a nosedive, and never recovered. :no: The Zenith brand and logo, which continued to appear on Zenith color TVs from the '90s through the early 21st century (which were fraught with problems, such as CRTs that shorted after two years, taking the entire video chain with them), had been reduced to a mere marketing symbol. The company is now completely out of business, never to be heard from again. :no:

06-13-2017, 11:15 PM
is on the correct frequency (15,750 Hz)

Close enough - My CET testing back in the 80s taught me the NTSC standard is actually 15,734 Hz....

Probably the best explanation on the web:

And the vertical rate is actually 59.94 Hz....:sigh:

It was a trick question on the ISCET Journeyman CET test for Consumer Electronics back in 1987...sadly, even I got it wrong, but still passed with a score of 97.

Zenith Electronics is still around, a wholly owned subsidiary of LG Electronics, which bought Zenith little by little.....

06-14-2017, 12:04 AM
Zenith Electronics is still around, a wholly owned subsidiary of LG Electronics, which bought Zenith little by little.....

Apparently still active in the US mostly as an R&D facility. You can thank them for ATSC 3.0!


06-14-2017, 02:55 PM
Apparently still active in the US mostly as an R&D facility. You can thank them for ATSC 3.0!


If you recall, Zenith was the forerunner of HDTV, pay-per-view, and subscription TV. Remember the Zenith SSAV cable descramblers?

06-14-2017, 09:15 PM
Yes, I do recall the Zenith SSAVI descrambler units, made for use with cable TV systems of the '70s or so to descramble, for a fee, pay-TV movie channels and such. (A subscription TV channel in Cleveland in the late '70s-'80s used a version of these descramblers to unscramble their STV services, called Preview; the service also made use of a special cut-to-channel TV antenna just for that station, channel 61.)

However, my point was that Zenith is in fact out of business as far as the manufacture of TVs is concerned. As I mentioned, their name and logo were still being used on television sets made by Goldstar as late as the late '90s and the first couple of years of the 21st century.

I remember reading about the Zenith Radio Corporation's first (and only, to the best of my knowledge) attempt at pay TV, known as Phonevision. (I knew someone in the '70s who had a 1954 Zenith console b&w TV with a Phonevision socket, but to the best of my knowledge the person, who lived in suburban Cleveland, never used it and may not have even been aware of Phonevision at that time.) This system may have worked well at the time (1950s), given the state of the art then, but in all honesty, today's pay TV services would almost literally run rings around Phonevision (if the latter were still in existence, which of course it isn't), since they can provide better pictures (in color, for one thing) and more features than could Zenith's system.

I was not aware, however, that Zenith's R&D division was responsible in large part for ATSC 3.0, the new DTV standard. In fact, I was not aware, until I read the posts following mine in which the statement was made that Zenith is still very much alive and well in the 21st century (albeit no longer as a television manufacturer), and that the company was instrumental in the creation of the new DTV standard. I looked at Zenith's website before starting to write this and was amazed at what the company is still up to in this century, after thinking for years that Zenith was dead, never to return.

Thanks so much for letting me know that Zenith, which for decades was my favorite make of TV and stereo gear, is still alive and well in 2017 (and I hope for many years to come), although not as a manufacturer of TV sets or other home-entertainment gear. I knew Zenith's TV manufacturing plant, now (late '90s-early 21st century) making Goldstar TVs under their own brand, was in trouble ("the handwriting was on the wall", so to speak) when I read about the company's last TVs, made in the late '90s-early 21st century, having problems with CRTs that shorted after one or two years, taking the set's entire video chain with them; I recall as well that these sets had HV regulation and other problems. :no: