My K731 came...
 

...and it looks surprisingly good.

The front is pretty clean although there is an area on the right where the finish has chipped. The fabric has pulled away on the top right, Not sure how to fix that. There is a dot near the 100Mhz point, does this help date the radio?

http://i31.photobucket.com/albums/c3...1/P3310004.jpg

The AM antenna is glued to the rear panel. You can see the electrical tape holding the wire connection close to the antenna windings. This must not be "as shipped" and I can only guess this is a "fix" of some kind. The connection seems to be a proximity pick-up of some kind and not directly connected to the wires. Is this right? I may try to hot glue the pick up to the coil unless someone has a better way to do this.

http://i31.photobucket.com/albums/c3...1/P3310001.jpg

The internals look OK, dirty and dusty though, but I can clean that up.

http://i31.photobucket.com/albums/c3...1/P3310002.jpg

The rear panel show the Zenith "Long Distance" logo.

http://i31.photobucket.com/albums/c3...1/P3310003.jpg

Which tubes are for the AM band and which are for the FM band?

http://i31.photobucket.com/albums/c3...1/P3310007.jpg

The AM band works fine but the FM is dead. Should I replace all the FM tubes or is there a way to figure out which tube is bad without a tester?

As you can tell I don't know radio electronics, so I sure appreciate all the help and tips you guys can give me to get this radio running again.

Thanks - Brad

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

http://i31.photobucket.com/albums/c3.../GreenWire.jpg

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...

If you need a schematic of the K731
 

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 #)

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

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?

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...

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.

AM Green Wire?
 

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

http://i31.photobucket.com/albums/c3...nAMAntWire.jpg

Tom, I am such a newbie! :scratch2:

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

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.

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

Here's your location
 

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

This is the location where I attached the green AM wire. Can anyone tell me if this is correct? It is connected to the same tab the blue wire (looks blue in phot, actually a shade of green) is attached to.

In this position I can make out AM radio stations, but they are very faint and I have to crank the volume up to 100%. There is a lot of static, and if I tap the radio I get more static each time.

Can anyone tell me which pin is #1 on a tube?

Thanks - Brad


http://i31.photobucket.com/albums/c3...reen1small.jpg