1972 Zenith color TV is back to life!

[drh4683]

Here's the '72 zenith. Its up and going again as of this evening. The new 6JG5 tube came in the mail today.
I replaced the 2.2K resistor in the cathode of the 3.58 osc. and the 68 ohm resistors in the chroma module which went up in smoke. Most likely due to the shorted out 6GJ5. After powering the set up, everthing was fine but no HV of any kind. The B+K analyst was used to clear the sweep transformer, which was all fine. This lead to troubleshooting at the horizontal output and back. There is supposed to be -58 volts at the grid (pin 5) of the 6LB6, which was actually running at +150 volts!!! Flipped the set over and first thing was to check the plate voltage at the 6U10 horizontal oscillator tube. The voltage was non existant. B+ was at the other side of the 39K 1watt carbon resistor in the plate circuit. That resistor was wide open killing the plate voltage. It looked perfect though. Put in the new 39K and everything was back to normal. The belfuse connection was a bit intermittent though at the cathode of the 6LB6. Simply bent the prongs out on the socket and all was well. I had to pull the tuner out to clean it, and also had to detach it from the mounting bracket in which to put the sheild back on. This is where the original owner screwd up. There were two left over screws sitting inside the cabinet, which were intended to hold the tuner bracket to the CRT bezel up at the top. They can easily be loosened and then the tuner lifted and pulled out. Speaking of the tuner, I had to take a picture of that disturbing tag I saw. Made in HONG KONG!! The zenith super gold video gaurd turret tuner made in Hong Kong, say it isn't so! Zenith was ahead of its time in more ways than one. They were one of the pioneers in oursourcing US jobs, which is one of the things I'm not proud about with my favorite electronics manufacturer. If I'm not mistaken, the very LAST all USA made parts in a Zenith TV would be 1967. 1968 models started to use the portugese made deflection yokes. As the years went on, you see more and more foreign parts inside the Zenith TV's. Lots of capacitors from japan, yoke from portugal, parts from hong kong like the delay line, tuners. I wonder what the zenith employees thought about that back then. The concept of outsourcing was relatively new then. I don't know when I first started to see Hong Kong made turret tuners though, this must be one of the first. My '70 models have USA made turret tuners. However, UHF tuners I've seen made in Tawain since the '68-'69 models. They were obviously made in a Zenith plant though, the quality is still there, just like the Taiwan made B+W sets from the early 70's.

Anyway, now that its fixed, its a typical zenith performing TV. Perfect picture. Just need to touch up the convergence and pincushion phase. All voltages test within spec at the oscillator and output tubes. This TV is getting its last gasp of true NTSC TV!

Pics are of the 25CC50 chassis, which I think is a pretty neat chassis. This one has 12 chassis tubes, 10 plug in transistors and one IC. I like these hybrid sets with the single duramodule. This chassis is very similar to the 1970 12A12C52 which is my favorite TV chassis. '72 is the last year for this style of chassis.

[JT-3]

wow, that is really impressive.

[Tony V]

As always, another example of Doug working his magic. A nice picture indeed! That chassis looks new. Fantastic job Doug!
-Tony

[radotvguy]

great job Doug

[zenith2134]

All that dust is Made In USA at least, lol.

Excellent cleaning and repairing job, that picture looks new!

[radiotvnut]

As usual, excellent job! Very nice picture!

[zenithfan1]

Very nice job Doug!

[radiotvnut]

Doug, I forgot to ask. Can we pretty please see a youtube video of the repair procedure?

[rcaman]

well i was thinking of my next vacation would be a storm chaser tour i love watching storm chasers on discovery channel. but i think it would be worthwhile to visit dougs soon to be tv museum. steve

[radiotvnut]

Originally Posted by rcaman

well i was thinking of my next vacation would be a storm chaser tour i love watching storm chasers on discovery channel. but i think it would be worthwhile to visit dougs soon to be tv museum. steve

How about lets both ride up there together.

[Jeffhs]

Originally Posted by drh4683

the quality is still there, just like the Taiwan made B+W sets from the early 70's.

This TV is getting its last gasp of true NTSC TV!

'72 is the last year for this style of chassis.

1. Yes, I know what you mean about the picture quality from the Taiwan-made Zeniths of the 1970s. I had one, a Zenith 12" SS portable, that I purchased new in 1978. It lasted 22 years and was still working almost like new, great picture and all and an exceptionally strong CRT, when I gave it up in 2000 (no room for it in my apartment, as I already have 2 color TVs, one of which is a 13-year-old Zenith Sentry 2--also working exceptionally well but not used much, except for cross-checking on those rare occasions when my cable goes out). Only thing wrong with the 12" SS set when I gave it up was the detent mechanism on the UHF tuner, which had broken some years before and jammed the tuner on one channel. Other than that, the set worked very well, which surprised me because at 22 years, most smaller portables are either on their last legs (CRT so weak it might as well be completely dead, etc.) or have developed serious chassis problems and have been trashed.

2. It's a good thing you have a screen shot of NBC Weather Plus+ in the thumbnails below your post, as these are literally the last days of that service. NBC is discontinuing Weather Plus+ at the end of this month, since the network acquired The Weather Channel not long ago.

3. You can still use every one of the TVs in your collection after Feb. 19, 2009 without losing the Space Command remote functions, unless you want the digital channels above 99. Just have your cable company connect the cable directly to the TVs' VHF antenna terminals through a 75-to-300-ohm matching transformer. (The only downside to this is the mess of cables and splitters you'll have going to all those sets if you go this route! ) This connection will give you all of Chicago's local VHF channels. The only ones you may not see are the city's UHF stations, although you could see them if they are downconverted to channels between the locals, as they are in most areas. For example, in my area near Cleveland, the CBS affiliate on OTA channel 19 is on channel 4 on Time Warner cable, the MyTV affiliate (OTA 43) is on 6, the PBS station (OTA 25) is on 10, and The CW (OTA 55) is on 9. The only local station that shows up on a channel above 13 on the cable here is Univision, OTA 61, which is found on cable channel 18. I actually like the idea of the network stations being in numerical order on TW cable--the NBC station on channel 3, CBS on 4, ABC on 5, MyTV on 6, FOX on 8, The CW on 9, PBS Cleveland on 10. Nice and orderly now. No more having to switch between VHF and UHF tuners; I like it, a lot. At first I didn't care for CBS channel 19 being on cable 4, but after realizing that the network stations are now all in a nice neat row on the cable, I've changed my mind. I've looked at the channel lineups for other cities served by Time Warner and have noticed as well that in many of these areas, the channels are arranged in a similar way. I think TW has the right idea, grouping all the network stations together so viewers don't have to go searching all over the so-called "dial" anymore to find them. They have done that with the digital channels as well. Kinda' has me wondering whether other cable systems will follow suit eventually, if they haven't done so already.

[AnalogDigit]

Great job. Very impressive! Better looking than a flat screen TV!

[freakaftr8]

Doug thats a nice picture! How is it that you seem to find sets and the CRT's are still in great emission! You lucky dog!