View Full Version : The massive 1975 Zenith combo has arrived...


drh4683
04-23-2011, 06:05 PM
It arrived from Oregon yesterday, survived the trip with no issues. Delivered in a covered trailer, pouring rain all day yesterday. This TV is massive, its one of the heaviest TV's I've ever lifted. Thank god I didn't have to bring it down any stairs otherwise I wouldn't take it. Its in very nice shape but of course, the stereo is not in 100% working condition. The left channel is much weaker than the right, however, the right channel alone will blow you out of the room with just a touch of the volume control. Upon taking the back cover off, I was extremely impressed with the stereo receiver and amp. That combined with a 25EC58 TV chassis = the absolute best TV ever created. Such high build quality, its very impressive to look at.
Certainly the grand finale for Zenith when it comes to building a top notch unbeatable product.

The TV works fine as does the space command. Cost $1425 new back in December '74 but had to be ordered as the set was not built until March '75.

https://lh5.googleusercontent.com/_ta1B_ryr8bE/TbNWeK8NvLI/AAAAAAAACLE/SV44QywpZL8/s800/DSC00124.JPG

https://lh3.googleusercontent.com/_ta1B_ryr8bE/TbNW0iOVsSI/AAAAAAAACL4/y3Ee9NbqYuE/s800/DSC00155.JPG

https://lh5.googleusercontent.com/_ta1B_ryr8bE/TbNWeUBoTsI/AAAAAAAACLI/bFGkPpAyn2k/s800/DSC00125.JPG

https://lh3.googleusercontent.com/_ta1B_ryr8bE/TbNWg12so4I/AAAAAAAACLM/oQ_rH-j__sI/s800/DSC00126.JPG

https://lh3.googleusercontent.com/_ta1B_ryr8bE/TbNWiATH8EI/AAAAAAAACLQ/gEYggrYXIxs/s800/DSC00130.JPG

https://lh4.googleusercontent.com/_ta1B_ryr8bE/TbNWb6WhcFI/AAAAAAAACK8/EE3QazjBLZQ/s800/DSC00121.JPG

https://lh6.googleusercontent.com/_ta1B_ryr8bE/TbNWdvmoS2I/AAAAAAAACLA/VyG15v_zl2E/s800/DSC00120.JPG

https://lh6.googleusercontent.com/_ta1B_ryr8bE/TbNWnGKyPzI/AAAAAAAACLY/4fKjTtoPK_0/s800/DSC00135.JPG

https://lh5.googleusercontent.com/_ta1B_ryr8bE/TbNWo196HCI/AAAAAAAACLc/Zue09H3VUjo/s800/DSC00136.JPG

https://lh3.googleusercontent.com/_ta1B_ryr8bE/TbNWpYNCe9I/AAAAAAAACLg/_N7Xem8t4tA/s800/DSC00138.JPG

https://lh5.googleusercontent.com/_ta1B_ryr8bE/TbNWtmFbOOI/AAAAAAAACLk/9PblRaJmj1c/s800/DSC00140.JPG

https://lh6.googleusercontent.com/_ta1B_ryr8bE/TbNWwafpexI/AAAAAAAACLo/Uy2ATS4UirM/s800/DSC00143.JPG

https://lh4.googleusercontent.com/_ta1B_ryr8bE/TbNWwuDOg4I/AAAAAAAACLs/kGLquT0-vZk/s800/DSC00146.JPG

https://lh4.googleusercontent.com/_ta1B_ryr8bE/TbNWz-cBgRI/AAAAAAAACL0/OgZiz5-08RY/s800/DSC00154.JPG

https://lh3.googleusercontent.com/_ta1B_ryr8bE/TbNWzuthmeI/AAAAAAAACLw/bVtrxDPNFtY/s800/DSC00165.JPG

ChrisW6ATV
04-23-2011, 06:25 PM
I did not realize anyone was making varactor-tuner TVs that far back. Very interesting. I wonder when the first set was sold with the array of pots like this?

sampson159
04-23-2011, 06:56 PM
wish i would have gotten this when he called me.glad another aker scored it.the best color set ever made bar none.beautiful.

Sandy G
04-23-2011, 07:09 PM
Beautimus !! (grin)

radiotvnut
04-23-2011, 07:22 PM
That's a fine looking piece of equipment! Glad you were able to save it!

DaveWM
04-23-2011, 08:53 PM
thats one sweet looking setup, I would check the output caps on the AMP, the speakers are cap coupled. Normally I am not a fan of slide controls, but on that tuner they just look cool. The TV pic looks great!!

JCFitz
04-23-2011, 08:59 PM
That is a beautiful set and the picture is fantastic.

Findm-Keepm
04-24-2011, 12:12 AM
Dave is right! Get rid of them dreaded Callins caps (black bodies with red ends) and you'll likely solve your level issues.

Dat ting is a beast! Keep us posted!

Cheers,

CoogarXR
04-24-2011, 06:58 AM
What does it have for speakers?

drh4683
04-24-2011, 11:15 AM
Here's what the amp and receiver are all about. Actually, there is not a single callins cap in this thing. I was surprised but I guess they were done with those by this time. Interestingly enough, many of the parts on the amp and receiver have 1973 date codes on them... I would guess that not too many of these sold and there was quite a warehouse full of parts and/or complete chassis' to use up? Keep in mind, this TV was built in March of '75.


https://lh5.googleusercontent.com/_ta1B_ryr8bE/TbRKNaeXnSI/AAAAAAAACMU/LmPhuSM_5is/s800/DSC00193.JPG

https://lh6.googleusercontent.com/_ta1B_ryr8bE/TbRKPYWMMBI/AAAAAAAACMY/JYiq_fcYcKc/s800/DSC00201.JPG

https://lh5.googleusercontent.com/_ta1B_ryr8bE/TbRKUbBn1eI/AAAAAAAACMg/0rkyLR1ltGU/s800/DSC00205.JPG

https://lh5.googleusercontent.com/_ta1B_ryr8bE/TbRKWS3TNgI/AAAAAAAACMk/kGeii5wRqII/s800/DSC00206.JPG

https://lh4.googleusercontent.com/_ta1B_ryr8bE/TbRKZTkO0HI/AAAAAAAACMo/vJMC-WwWe_8/s800/DSC00208.JPG

https://lh6.googleusercontent.com/_ta1B_ryr8bE/TbRKej2jN7I/AAAAAAAACM0/E8qWu7Ubw80/s800/DSC00222.JPG

https://lh3.googleusercontent.com/_ta1B_ryr8bE/TbRKdXVpqHI/AAAAAAAACMw/AFbmB0NHlUA/s800/DSC00221.JPG

https://lh3.googleusercontent.com/_ta1B_ryr8bE/TbRKcKOeqNI/AAAAAAAACMs/eeVOizqLYB4/s800/DSC00219.JPG

DaveWM
04-24-2011, 12:47 PM
wow that all looks very well made, hard to believe PTP still being done in the mid 70's!

zenithfan1
04-25-2011, 11:02 AM
Awesome set Doug! I'd like to have that tuner/amp setup so I could build custom cabinets and make cool separates. The only thing is, I can never bring myself to mutilate such nice stuff like this:no: Maybe when a beat up one shows up.....
Great save!!!

Adam
04-25-2011, 03:34 PM
I must have been looking at this before I fell asleep, I had a dream last night that I found at a thrift store a Zenith console that had this radio and amp unit in it, but no tv or phono. It looked like this console, but with just 3/4 the speaker area, and no tv in the middle. The radio unit was mounted on the top, like here, but in the middle of the cabinet.

And next to it was a Zenith porthole console!

I wonder why it is that in the 50s-70's no one was making just a regular console radio without the phonograph. I'd like to have one if they existed.

freakaftr8
04-25-2011, 04:30 PM
Now that is a beautiful example of american history!!! Nice set Doug, well worth the trip from Oregon..

DaveWM
04-25-2011, 04:36 PM
how have the slide controls held up? I often find them loosey goosey or not very smooth.

drh4683
04-25-2011, 05:51 PM
thanks all,

The slide pots seem OK for the most part, not too loose. Slide controls were always gimicky in my book and never practical and always subject to intermittents and breaks in the carbon trace. They are simply eye candy in this case with the colors around them that light up. Since I have no control over the treble, I did test the pot and it was working. However, all of the 1uF@50v lytics were shot. ESR off the charts. The caps are cheap, made in Taiwan with the brand name of "Richey". The nichicons are all pretty decent yet but I've got about 10 of these Richey lytics to replace. That should bring my treble back and quite possibly even my lack of stereo balance/output on the left channel. I could clearly tell these richey caps were being used in a left channel and right channel circuits within the receiver as I was seeing two identical circuits with the way the components were configured. Like I said before, the left channel works, but the output is much weaker than the right. I did test the TO-3's on the amp chassis. I did detect much higher leakage in one driver vs the other, not sure which channel was which. Im kind of doing this troubleshooting blindly as I don't have a schematic for this particular receiver and amp. Im hoping to just stumble across a bad transistor and/or cap simply by basic test methods using my sencore super cricket for the transistors (out of circuit), and the dicksmith ESR for the lytics. So far, the gain on all the transistors have been excellent but like I said, I noticed much higher leakage on one of the TO-3 drivers. The one transistor (121-793) measured about 20uA leakage and the transistor of the other channel was almost 100uA. Quite a difference. Lytics and resistors in the amp seemed good when doing mirror image comparisons between the channels. These TO-3's are germanium too, didn't know that junk was still being used in the mid 70's. Not a fan of germanium transistors:thumbsdn:

Findm-Keepm
04-25-2011, 08:11 PM
Doug, are the outputs germanium too? I can see the Motorola drivers would be, but those outputs were made by Delco, who had graduated to all-silicon by 1970. Some of the later high-power Zenith Allegro units used a similar amp, with Delco outputs. DTS-701's, IIRC, and Zenith's replacements were all Delco straight up, with no 121- markings. Those little IEC-branded black caps were called firecrackers back in the day - the mantra was "replace all of the Callins and Firecrackers....and it'll be fixed."

I'll do some digging tomorrow - I may have the Zenith lit for your unit. My stuff runs through 1972, and gets spotty after that, with the exception of clock radios and record changers. I'll also check my deep storage for the Zenith drivers - you can always replace them with ECG/NTE 121's. We used a stash of 2N1558's we had - good Motorola PNP Germaniums made for military aircraft inverters. They were surplused by the thousands when Vietnam wound down.

Lemme get to checking for you - Cheers,

dieseljeep
04-26-2011, 09:18 AM
My Heathkit power inverter still uses Motorola Germanium transistors. Has a 1971 code date.

rca2000
04-26-2011, 10:36 AM
Doug, in one of my Zenith HI-FI manuals, it speaks on how to convert the germanium transistors to the silicon ones on that amp--some tech wrote it in there.

From what I remember--it involves changing, and in some cases, shorting over, some resistors in the output/driver ckt, and replacing them with MUCH lower values, and putting in sils. for the transistors, probably ECG-219 or so.

But, I have to ask...just WHAT is wrong with germanuim transistors anyway?? I have a couple of the Zenith stereos and several amp, or one-piece chassis with germaniums. In the big sets like ours--those amps sound VERY nice and powerful with those gers. in them? Why change them--if they are ok??

Jeffhs
04-26-2011, 12:05 PM
Glad to know that your Zenith console made it from Oregon to Chicago unscathed. It was a good thing the trailer the set was in was covered, if you say it was raining cats and dogs the day it arrived at your house.

I am nothing short of amazed that Zenith had built the stereo section of your TV on a PC board, with the television set itself being hand wired. If they hand-wired the TV, I would have expected the stereo to have had point-to-point wiring as well. I could never understand why they went back to PC board construction for their radios even as far back as the Royal 500 series of the 1950s. I have a Zenith R-70 AM/FM portable radio, made in 1980, with the entire set, except the speaker and controls, on a PC board; however, my 1958 Zenith Royal 1000 Transoceanic portable is hand-wired, with a metal chassis and plug-in transistors, and it is heavy as the dickens even without batteries. Strange that Zenith would abandon point-to-point hand-wiring after all their years in radio and TV in favor of PC board construction; with the reputation for quality their hand-wired sets had earned over that time, their reversion to PC boards seems to me like a step backwards.

Does your set have the original CRT? If so, it must have been one of Zenith's best. Until now, I had never heard of or seen any TV set with a 36-year-old CRT that still works as well as yours seems to. The screen shot of the weather forecast (looks like it's from The Weather Channel) on your set looks great, almost like new. That's why I doubt that the TV has the original CRT. If it is in fact the original tube, the set's former owners must not have used the television much, except perhaps for the evening news. It is also possible that they gave up on the set when DTV arrived in June 2009, before ATSC->NTSC converter boxes were available.

BTW, I wouldn't change anything in the stereo tuner/amplifier if it is working well (unless, of course, you are troubleshooting the problems with the one weak stereo channel and the inoperative tone control, as I'm sure you are or soon will be). Speaking from experience, modifying or trying to improve a radio, TV or anything else that is operating perfectly well can, and often does, lead to big problems, with the unit operating worse (if it works at all) after the modifications than it was working before you started.

DaveWM
04-26-2011, 02:29 PM
if its like other zenith combos the TV does NOT use the tuner amp, but rather has a cut out switch the disconnects the speakers from the amp and switches to the TV based audio (and may or may not kill power the the stereo tuner/amp). On mine I made up a a new wire harness that bypassed that and just drove a small interanl speaker (there was a place for on) from the TV audio and left the main spearker connected to the amp. this way I could power up the amp and drive the L and R directly from my video source. it REALLY makes for a nice setup with that powerfull amp in true TV stereo sound. I would just use the tape inputs. I left the small speaker hooked up so you would just leave the TV volume turned down. I did not want to have the audio stage unloaded. The entire process was just done by the new wire harness, I even left the old one in place so it would be easy to return to the orig setup, if for some reason that would ever by desired.

Carmine
04-27-2011, 10:44 AM
I would be interested in how to do that conversion too, because I think all of my germanium transistors are shorted in my Emperor.

bgadow
04-27-2011, 10:59 PM
I didn't realize they used the flat chassis that late, or a stereo chassis like that, for that matter. The latter looks American made-is it? Very, very impressive. It was all downhill from here.