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 Post subject: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Mon 17, 2019 7:51 pm 
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Joined: May Tue 05, 2009 10:21 pm
Posts: 353
Location: West Windsor, NJ 08540
Hi Guys,

I finally started working on my Zenith Royal 755LK lunch box radio that been waiting to be recaped and aligned. As soon as I removed the chassis I noticed that there was a hole in the center of the cone and also that the ferrite rod antenna had a break in it.

Need some advice on how to repair the felt type material that's in the center of the cone.

Any suggestions on how to repair this hole ?

Frank


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Zenith_Royal_755_Front_1ss.jpg
Zenith_Royal_755_Front_1ss.jpg [ 247.57 KiB | Viewed 463 times ]
Zenith_Royal_755_Top_view_1sss.jpg
Zenith_Royal_755_Top_view_1sss.jpg [ 237.32 KiB | Viewed 463 times ]
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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Mon 17, 2019 8:37 pm 
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Joined: Aug Wed 24, 2011 4:35 am
Posts: 4426
Location: Sunnyvale CA
Frank512 wrote:
Hi Guys,

I finally started working on my Zenith Royal 755LK lunch box radio that been waiting to be recaped and aligned. As soon as I removed the chassis I noticed that there was a hole in the center of the cone and also that the ferrite rod antenna had a break in it.

Need some advice on how to repair the felt type material that's in the center of the cone.

Any suggestions on how to repair this hole ?

Frank


Usually, the fibers aren't missing, just pushed to the side, so, bend a paper clip or use an Allen wrench to get behind it, gently, and pull them out, gently. Once you can see the end of the fibers, put some a tiny bit household cement (Duco cement or something like it, or balsa model airplane cement like Ambroid or SIGment) on the edges of the cut fibers, tease them up into close contact so the glue will go across the cuts, and then let it dry. As it dries, it will shrink a bit and pull them close to level.

Alternately, go get some thin felt, cut out a new circle, and glue it around the edges, over the existing felt. It would probably be possible to remove the old felt and replace it with the judicious use of acetone to dissolve the glue, but the problem might be that you dissolve all the other glue holding important parts together at the same time.

It's essentially only cosmetic, this felt is there just to keep dust and magnetic particles out of the voice coil area. If you drip glue or acetone in the wrong place, you can wreck the entire thing. A third alternative is to just leave it alone, it will work fine with a hole in there unless something gets in there and jams it up.

Brett


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Mon 17, 2019 9:26 pm 
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Joined: May Tue 05, 2009 10:21 pm
Posts: 353
Location: West Windsor, NJ 08540
Hi Bret,

Thank you so much for the great info.

Found a solution for patching the hole in the speaker cone.

Went to Walmart and found some felt pads for chairs for $1.47


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Mon 17, 2019 9:52 pm 
Member

Joined: May Tue 05, 2009 10:21 pm
Posts: 353
Location: West Windsor, NJ 08540
Here is a picture with the speaker hole patched.


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Speaker Cone repair.jpg
Speaker Cone repair.jpg [ 259.77 KiB | Viewed 441 times ]
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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Tue 18, 2019 3:45 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5941
Location: Indianapolis, IN
Hey Frank,

Been a long time since you've posted here---welcome back !

You'll like that radio once complete---excellent performer and good sound !

Did you add any glue to that felt disk ? Don't know how long that adhesive back will hold on with the movement of speaker cone...

John


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Tue 18, 2019 5:28 am 
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Joined: Oct Mon 02, 2017 8:53 am
Posts: 152
Location: Panama City, FL 32401
Hello Frank, nice looking 755. The same thing happened to me with the middle of the felt being torn on my 750. Apparently the hooks that hold the Zenith badge on the front somehow cut into it. It doesn't affect the sound fortunately. Don't know if any other lunchbox series radios had that happen.


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Tue 18, 2019 5:35 am 
Member

Joined: May Tue 05, 2009 10:21 pm
Posts: 353
Location: West Windsor, NJ 08540
Hey John.

Yeah, its been a while. Bought a new house and in the meantime I've been busy cleaning up the old house and packing things up.
I saw your Zenith Royal 800 post, great job you did refurbishing it, looks beautiful.

I cut a thin slice off the felt pad and glued it on with GGorilla glue. Also started to recap it, probably will finish up the recapping tomorrow.
The ferrite rod is broke so I am thinking about either glueing the rod antenna back togeather or rewinding a new ferrite rod antenna on a new rod.

I will definitely let you the progress that I make.

Frank


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Tue 18, 2019 5:41 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5941
Location: Indianapolis, IN
Thanks Frank !

Superglue gel works excellent on those ferrite rods if it is a clean break---have repaired several now and all are fine.

That felt pad should never come off with Gorilla glue !

Wasn't aware that you were planning to move---congrats on new home ! Are you still in same area ?

John


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Tue 18, 2019 3:46 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 13826
I've seen felt eaten away in transistor radios by tiny beetles, paper fine. All that was left was a bit of their remains, apparently grew too large to escape.

_________________
Tom


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Fri 21, 2019 12:43 am 
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Joined: May Tue 05, 2009 10:21 pm
Posts: 353
Location: West Windsor, NJ 08540
Hi John,

I finished patching the speaker hole and also finished replacing all of the electrolytic caps and I guess the next challenge will be repairing or replacing the broken loopstick antenna. In the past I have used Gorilla glue with good results but on this loopstick a few of the windings got damaged.

Update: I glued the loopstick back togeter and remeasured the inductance and now it reads 370 uh. I will reassemble the radio and see how it works in a few days.


Last edited by Frank512 on Jun Mon 24, 2019 2:49 pm, edited 1 time in total.

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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Fri 21, 2019 4:22 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5941
Location: Indianapolis, IN
Hey Frank,

If the windings didn't break and no wire is missing, you should still be able to glue that back together, gently work the windings back into position, and re-flow the wax with soldering iron. Have done that myself, including a ferrite-rod with multiple breaks within winding areas and they turned out fine---just takes care and patience to align rod sections with the tension of wire working against you. I would recommend Superglue gel, though, since it sets very quickly once broken ends "mate" properly...

Good luck !

John


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jun Fri 21, 2019 4:55 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 31985
Location: SoCal, 91387
Super Glue is the best for fixing broken ferrite cores. AFA the coil winding, a few turns less shouldn't really affect performance. I'd try gluing it back together, and tying the remaining broken coil leads together.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jul Mon 08, 2019 4:20 am 
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Joined: May Tue 05, 2009 10:21 pm
Posts: 353
Location: West Windsor, NJ 08540
Hi guys,

I used the gorilla glue and in the process of re-assembling the radio the ferrite rod antenna broke again.

Well, we will try again glueing back the broken ferrite rod antenna using super glue or epoxy.

Hope it works this time !


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jul Mon 08, 2019 4:35 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5941
Location: Indianapolis, IN
Hey Frank,

When I saw that you posted, thought the radio was finished ! Yes, Superglue should work much better if you're able to get the broken sections to mesh correctly and tightly...

Good luck !

John


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 Post subject: Re: Zenith Royal 755LK Lunch Box Radio Project
PostPosted: Jul Mon 08, 2019 6:17 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 31985
Location: SoCal, 91387
Super Glue DOES work on ferrite rods.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


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