Zenith K731, My first post

[Sandy G]

The earlier-late '40s ones were, I think...

[Nolan Woodbury]

This question has nothing to do with radio, but how to you guys get these big, nice photos to upload? The window I use to post pics here restricts to a very low pixel count, which looks like a postage stamp when placed. I have nice pictures to show!

....back to the K731 talk. Brad, your Zenith looks swell! Love the dark, almost cherry finish and that cabinet is the style I favor. The antenna leads should be soldered, and I'd check the paper caps underneath for leakage. The big, series dude on top should be checked too, but those seem to last a lot longer. You'll have to pull the chassis to see them and don't forget to keep it unplugged; these are fully hot when connected.

Nolan - I use PhotoBucket.com to store my pics. Thanks for the tips but I right now I have much simpler problems.

Where does the green wire off of the antenna go? I can almost make it out in one of my pics but I am not quite sure.

Brad

[Tom Bavis]

The 12DT8 is the only tube used for FM, and not AM. So try it first.

The dot before 100 is for Zenith's own FM station in Chicago. A handy dial calibration point at the factory?

See if there's a wire broken off at the tuning cap - could be where the green wire goes, since the white wire doesn't...

Go here:
http://techpreservation.dyndns.org/s...ics/Zenith.htm

And choose 7m07 as the model number. (I'm fairly sure this is the model #)

[Chad Hauris]

Tube function:
12DT8 FM RF amp and convertor

12BE6 AM convertor

12BA6 1st IF

12BA6 2nd IF

12AU6 FM limiter (3rd IF)

14GT8 or 19T8 FM discriminator, AM detector, 1st audio amp

35C5 audio output

[Blooze]

Nice radio. Mine is the 7K07 chassis and I'm still trying to find a schematic that actually matches the radio. I've looked at the 7M07 and the tubes are slightly different, but the rest might be the same? Any suggestions?

[Jeffhs]

Originally Posted by Tom Bavis

The 12DT8 is the only tube used for FM, and not AM. So try it first.

The dot before 100 is for Zenith's own FM station in Chicago. A handy dial calibration point at the factory?

That little white dot can also be used as an alignment aid if you ever have to realign the set. The symbol marks 99.5 MHz and was, as mentioned, the frequency of Zenith's owned and operated (O&O) FM in Chicago in the '50s through about the mid-'70s. The station was known as WEFM in those days; it is now WUSN, "US99" C&W (country/western). Most of Zenith's radios from the '50s until the end of the '70s had the dot at 99.5, but by 1976 or so this was just a carryover from an earlier time (the WEFM era) and was kept on the radios only for nostalgic value. Both my Zenith K731 and C-845 have the 99.5 marker on their slide-rule tuning dials, but the '845 has two parallel horizontal lines, rather than a dot, at this point. My C845 also has the two parallel horizontal lines on the AM tuning dial at 640 and 1240 kHz (the old Conelrad emergency warning frequencies) in addition to the Conelrad symbols themselves. One version of the K731, probably a slightly older version than mine, has the CD symbols on the AM tuning scale (my set does not have these icons, so perhaps it is one of the newer models made after 1963, the year Conelrad was abolished in the U.S. in favor of the Emergency Broadcast System).

[Nolan Woodbury]

Off hand, I don't know where the green one attaches Brad, but I have a K731 handy to peek inside if needed. PM me or respond if you need me to track this down-

Thanks for the kink...I now realize if you pull photos from a URL, there's no size restriction...

[Tom Bavis]

7K07 chassis is coverd in Sams folder 653-12
7M07 is in 778-10

Check with your library, or the online sources I have mentioned elsewhere.

Originally Posted by Tom Bavis

7K07 chassis is coverd in Sams folder 653-12
7M07 is in 778-10

Check with your library, or the online sources I have mentioned elsewhere.

Tom, I am such a newbie!

What is Sams folder?

I was able to get a Djvu schematic "Model T350 R & W Chassis 7M07". I hope this is the correct one?

Thanks,
Brad

[wa2ise]

That green wire from the antenna should connect to the part of the tuning cap that is also connected to pin 7 of the 12BE6. You may have it connected to the oscillator coil section by mistake.

Nolan-
I can't figure out where the green AM antenna wire goes. I do have a schematic of the chassis but with my limited knowledge of electronics, it doesn't help much.

This is where I attached it, but it doesn't seem to fix the problem. The AM worked well until this wire fell off. The wire is attached to the tuning capacitor now, but this must be wrong since I still have can't receive the AM band. I took 12BE6 out to get a better photo.

Once I get this running again, I'm going to give it a good dusting!

Thanks for your help.

Brad

[Tom Bavis]

The antenna wire should connect to the capacitor section with larger plates.

Sams published (and still does!) the "Photofacts" folders - most service shops subscribed. Each one is 4-16 pages - schematic, parts list, photos. You can buy them from Sams ($25 or so...), but there are a lot of copies out there - I have over 1000 myself, most gotten for free.

Online sources:
michelletroutman.com
infotronix.us
findatube.com

[Nolan Woodbury]

All of the posts regarding the location are correct, but these pictures should clear it up nicely.

http://i78.photobucket.com/albums/j100/nolanwoodbury/K731C.jpg

Note that the wire connects to the tuning cap, then runs a separate wire that loops through a hole in the bottom of the chassis that connects to (I believe) pin 7 of the 12BE6. Not sure of this, 'cause the markings are worn and this radio has no tube identifier-label on the bottom. Still, it's the tube closest to the tuning mechanism.

http://i78.photobucket.com/albums/j100/nolanwoodbury/K731E.jpg