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PostPosted: Nov Fri 06, 2009 6:46 pm 
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Location: La Porte, IN, USA
Breakthrough!
Have Radio Canada International booming in on 9.615 Mhz on Band 5 of the set.
Had a a dead tuner module--which the manual says to just change. The manual has no directions for dis-assembly or repair of the A1A1 Tuner module, so I thought I was dead in the water. But I started taking out cover screws and removed a small cover from the module and found the B+ lead broken off and dangling. Soldered it back on and Wah Lah! ("VOILA!" )
Can tune stations fine on Band 5 ( 8.9 to 16 Mhz. )
Gears are messed up for channel band selector and band indicator, so that will be a really big PITA.
No AGC (AVC), but that should be fixable.
No BFO, but that should be fixable.
No Calibrator, but that should be fixable.
Rebuilt the 8.5 Volt regulator.
IF filter selector works well. Selectivity is razor sharp on "Narrow" position, and still quite sharp on "Wide" with good fidelity.

Looks like this set had a rough ride in-country. Pitting and corrosion of the module boxes. Some parts bent and/or broken.
But--IT LIVES!
Patience paid off--so far...
:) :) :)

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Last edited by OZ132HOME on Nov Fri 06, 2009 8:37 pm, edited 2 times in total.

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 Post subject:
PostPosted: Nov Fri 06, 2009 8:33 pm 
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Location: La Porte, IN, USA
Front bearing for the Band Selector "Gearbox" is shot--can't change bands with the panel Band Selector Switch.
Got the band shifted (with pliers) to Band 1, BCB, and broadcast stations come in great, with excellent selectivity and sensitivity.
AGC (AVC) works, for some reason on BCB. Did not appear to be working when I was on Band 5...

The Mechanical work--on the Band Selector and the tuning--is going to be even more challenging than the electronic repair.
I am really not good with precision mechanical work. Would rather take a sharp stick in the eye.

This set, made by Zenith for use by the USMC for signal intelligence gathering, is quite well designed, electronically at least.
With two tuned RF stages and 3 or 4 455 Khz IF stages on the first four bands, ceramic (Or mechanical?) IF filters it performs quite well on the BCB and lower short wave bands. On upper SW bands it is double conversion, and on the highest bands it uses a 10.7 Mhz IF and AM or FM detection. It is extremely well sheilded, each section a module totally enclosed in a tin box.
It bears little resemblance--electrically or mechanically-- to the Zenith TransOceanic, from which it is supposedly descended.
Or perhaps one might call it a ZTO on a large dose of Steroids...[/b]

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PostPosted: Nov Sat 07, 2009 6:56 am 
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Very cool indeed!
Keep going, you're doing great.

John


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PostPosted: Nov Mon 09, 2009 6:06 pm 
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Location: La Porte, IN, USA
Thanx for the encouragement, John. I can really use it.
Hate to see this particular piece of mil history not working properly.

Got gears meshed and able to select Bands 1 through 6, which all show signs of life.
Listened to several shortwave broadcasts stations last night.
Sensitivity and selectivity are on a par with a good communications type receiver.

The band changing gear box is the big thing right now.
Something to sub for that bearing?
Would rather be working on the gearbox for my 1960 Chevy---at least I could find all the parts I need at a local junkyard. Or a whole tranny!
With all the bumps and bruises this thing has, it feels as if something is bent out of alignment in the tuning shaft and/or gearbox. Very hard to turn...
When (if) I get that fixed, I need to find just the right sized "O" ring to use for a tuning belt, and figure out why in the world the frequency indicator tape only turns half as far as it should, while the actual tuner turns all the way from one end of the band to the other, as it should???

BTW, the tuning capacitor gang is quite unusal on this set. It looks just like a slug tuned variable inductance tuner--the kind they used in car radios. But the schematic shos clearly it is a gang of 8 variable capacitors. Very interesting...

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PostPosted: Nov Tue 17, 2009 3:35 am 
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Location: La Porte, IN, USA
Reception on Bands 1 through 8. Top two bands are AM or FM. FM detector working O.K.
Using an O ring for a tuning drive belt--this set uses a very unusual "Pic Belt" that looks (in the manual pictures) like nothing I've seen.
Fat chance I'll ever find a replacement. The O ring keeps sliding off the pulleys. Will post a picture from the manual, in case somebody has an idea...

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 Post subject:
PostPosted: Dec Tue 08, 2009 3:36 pm 
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Location: La Porte, IN, USA
This set has been temporarily shelved, til I come up with a tuning belt and a plan for replcing the gearbox front bearing.
Any ideas are still welcome...

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PostPosted: Dec Wed 09, 2009 12:57 am 
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Location: Nashville TN
Does the bearing have a number on it.If not you may be able to match it up at a bearing place.Orings look around to get one made for it or try cuting oring and glue or melt it back together.Just a thought.Sprman 8)

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 Post subject:
PostPosted: Dec Wed 09, 2009 2:11 am 
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OZ,
Do you have what is left of the old belt? If so, post a photo here with any dimensions and/or cog/tooth info so we can help locate a replacement.

John


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 Post subject:
PostPosted: Dec Wed 09, 2009 8:34 pm 
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Location: La Porte, IN, USA
No belt came with the radio, but a pic (from the manual) in on the way, soon as I get it up-loaded...
looks like an O ring with "teats" on it...

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PostPosted: Dec Wed 09, 2009 9:05 pm 
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Location: Mt. Airy, Maryland
Many printers and copiers use cogged belts. If you find one with the right tooth pitch, you should be able to slice it and patch it back together.


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 Post subject:
PostPosted: Dec Wed 16, 2009 9:25 pm 
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Location: La Porte, IN, USA
Here's a pic of the Tuning Drive "Pic Belt" from the TM manual:

Image

Ever see a drive belt that looks like that??? :?: :?: :?: :?: :?: :?: :?:

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PostPosted: Dec Wed 16, 2009 10:53 pm 
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Location: Freeport, LI, New York 11520
Here's a thought....

Is there anyway you can get those gears off the shafts? Then get a set of more common gears, the same diameter of course, that will accept a more available belt.

You may end up reinventing the wheel on this one yet!

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 Post subject:
PostPosted: Dec Thu 17, 2009 12:40 am 
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Location: Nashville TN
Looks like a belt used on Raymond electric forktrucks,to the encoder on the model 7400 AC. Sprman 8)

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 Post subject:
PostPosted: Dec Thu 17, 2009 12:50 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Sandpoint, IDAHO 83864
I bet a belt like that could be ordered from Stock Drive Products. They specialize in small motion control devices like this.
Curt

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 Post subject:
PostPosted: Dec Thu 17, 2009 2:10 am 
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"Ever see a drive belt that looks like that???"

Yes!

Doing some research.

John


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PostPosted: Dec Thu 17, 2009 3:00 pm 
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OZ,
Here's a supplier of belts
http://wmberg.smartcats.com/sc_app/default.asp?code=
If you look in the upper left of the photo on that page you'll see a belt like the one you need. You will need to get some info on the belt, like how many tooth it is and space between. Don't know if the TM gives all that.

You might email the company and give them the model of radio and part # of the belt from the TM and see if they can cross reference it.

Dave Ross gave me the lead. He bought a similar belt for his R-1490/GRR-17 from this outfit.

John


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 Post subject:
PostPosted: Dec Thu 17, 2009 6:58 pm 
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Location: La Porte, IN, USA
John,
Thanks so much. You are a gentleman and a scholar.
I really appreciate your help and encouragement.

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PostPosted: Dec Sat 26, 2009 8:26 pm 
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Location: Monterey California USA
Amazingly, there's another one on eBay right now, looks pretty complete with cabinet and assorted pieces. I see the crowd is going wild for it, too. Item #

280440978667

I think it may be a bit outside the forum rules to post an eBay # in this particular forum, but as the item isn't mine and the photos seem relevant, I thought I should mention it. Weird how various rare items seem to show up in bunches on eBay, at the same time, then disappear.

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PostPosted: Dec Sun 27, 2009 4:32 am 
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Location: La Porte, IN, USA
Geoff Fors wrote:
Amazingly, there's another one on eBay right now, looks pretty complete with cabinet and assorted pieces. I see the crowd is going wild for it, too. .


Sold for over $1K! Wow!
Image

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PostPosted: Dec Sun 27, 2009 2:33 pm 
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Location: Winchester, VA USA
Any receiver that has "7.24" as a PRINTED calibration has to be good!

Mike


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