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 Post subject: Dumont 1120 Clock Radio repair
PostPosted: Sep Mon 27, 2021 8:48 pm 
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Joined: Aug Tue 10, 2021 9:49 pm
Posts: 63
Location: Chesapeake, VA
 I'm restoring a Dumont 1120 clock radio.  Unfortunately all four screw posts have broken away from the cabinet.  I still have the broken posts attached to the screws.  Anyone know a good way to reglue the broken posts back to the cabinet?  Will JB Weld work??


Attachments:
Dumont 1120 9-26-21 broken clock posts 8.JPG
Dumont 1120 9-26-21 broken clock posts 8.JPG [ 717.28 KiB | Viewed 681 times ]
Dumont 1120 9-26-21 clock model 13.JPG
Dumont 1120 9-26-21 clock model 13.JPG [ 841.43 KiB | Viewed 681 times ]
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 Post subject: Re: Dumont 1120 Clock Radio repair
PostPosted: Sep Tue 28, 2021 12:28 am 
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Joined: Dec Thu 10, 2015 7:01 pm
Posts: 569
Location: Aurora, IL
I've had good luck repairing broken pieces like what you show using epoxy glues targeted toward plastics. J-B Weld has a two part epoxy called PlasticWeld. Loctite also has their own version. Their bond is very strong. If possible after gluing squeeze the pieces together with a small spring clamp or use a weight of some sort. If necessary use a piece of wax paper or parchment paper between clamp and glued piece if glue may ooze out of hole in plastic to keep clamp from sticking. Good luck!


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 Post subject: Re: Dumont 1120 Clock Radio repair
PostPosted: Sep Tue 28, 2021 5:53 am 
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Joined: Apr Sun 08, 2007 6:47 am
Posts: 5204
Location: British Columbia
It it's polystyrene plastic acrylic solvent cement from a plastics shop will weld the broken pieces of stud back together, with no clamps, which will result in a stronger bond, and a cleaner repair, then reaching for the J.B Weld, they sell it in some plastics shops. I don't know what it is about J.B but people seem to think it's the thing to reach for repairing anything, when it is not. It's almost as bad as this propensity towards using silicone on speaker cones, which should be left for caulking around the bathtub.
Regards
Arran


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 Post subject: Re: Dumont 1120 Clock Radio repair
PostPosted: Oct Mon 04, 2021 5:16 pm 
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Joined: Dec Sat 24, 2011 9:17 pm
Posts: 8555
Location: Vancouver Island, Canada
Agreed, solvent cement or airplane model glue, the stuff you shouldn't sniff.

The key here is to replace each piece exactly as it was before it snapped.
Those screws don't need to be torqued. It's not a truck wheel or cylinder head.
A firm but gentle touch on the screwdriver will do. :D

_________________
Watch the doughnut, not the hole.
Burl Ives, RIP, oldtimer.
[:l>)


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 Post subject: Re: Dumont 1150 Clock Radio repair
PostPosted: Oct Mon 04, 2021 6:55 pm 
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Joined: Aug Tue 10, 2021 9:49 pm
Posts: 63
Location: Chesapeake, VA
I'm gonna try SCIGRIP 10315 16 Acrylic Plastic Cement. I also just received a Bondic acrylic glue that UV light activated. I will test it out on some old plastic pieces, then give it a shot on at least one post.


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 Post subject: Re: Dumont 1150 Clock Radio repair
PostPosted: Oct Fri 29, 2021 4:40 am 
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Joined: Aug Tue 10, 2021 9:49 pm
Posts: 63
Location: Chesapeake, VA
I used SCIGRIP 10315 16 Acrylic Plastic Cement. Though it seemed to work well, it was very runny and hard to control. Having said that, it did seem to make a strong bond. I reinforced the repair with the Bondic acrylic welder. I also used the Bondic to build up and fill in gaps.

One post I had to form the post, used JB Weld inside a lubed piece of tubing. The bottom did not bond with the broken cabinet post but did conform to the jagged edges. After it set, I removed the plastic tubing....... with difficulty. Then I used the bondic and bonded it with cabinet.

I've been able to put the screws back in without breakage. Once I've finished the electrical repairs, I'll put the pieces back in and let you know the results.


Attachments:
Dumont 1150 post repair 1.JPG
Dumont 1150 post repair 1.JPG [ 2.7 MiB | Viewed 359 times ]
Dumont 1150 post repair 2.JPG
Dumont 1150 post repair 2.JPG [ 2.73 MiB | Viewed 359 times ]
Dumont 1150 post repair 3.JPG
Dumont 1150 post repair 3.JPG [ 1.98 MiB | Viewed 359 times ]
Dumont 1150 post repair 4.JPG
Dumont 1150 post repair 4.JPG [ 2.11 MiB | Viewed 359 times ]
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 Post subject: Re: Dumont 1120 Clock Radio repair
PostPosted: Nov Sat 06, 2021 5:20 am 
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Joined: Aug Tue 10, 2021 9:49 pm
Posts: 63
Location: Chesapeake, VA
I was able to reinstall both the speaker and the clock into the repaired posts. So far so good.

I completed the electrical repairs. Replaced the filter caps and the wax caps. I also had to construct the couplet, see pic. Before I started I measured the resistance reading on the couplet and found all of them way out of spec. So I built a new one.

The restored circuitry works very well except I do get a hum that I believe is coming from the clock. Any suggestions on how to suppress the hum?

I also need to find a knob for the clock that is the on off switch for the radio, see picture below. I've searched high and low and can not find one or one close to it on the internet. Any suggestions are welcome.

I'm considering going back in and installing Y safety capacitors. Do you think that is necessary??


Attachments:
Dumont 1150 couplet rebuilt 3.JPG
Dumont 1150 couplet rebuilt 3.JPG [ 2.08 MiB | Viewed 272 times ]
Dumont clock radio clock knob.JPG
Dumont clock radio clock knob.JPG [ 59.86 KiB | Viewed 272 times ]
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 Post subject: Re: Dumont 1120 Clock Radio repair
PostPosted: Nov Sat 06, 2021 5:06 pm 
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Joined: Dec Thu 10, 2015 7:01 pm
Posts: 569
Location: Aurora, IL
Excessive hum from the clock generally can come from two sources. One is if the coil winding is loose. A very low level hum is normal but the natural vibration that produces hum can become excessive if the coil is loose. Check to see if you can move coil freely. It should be fairly tight. They install a shim during manufacture to keep winding tight to metal core but can become loose over time.

Also make sure alarm is not currently set ON as it also be a source of hum if alarm is going off ( should be a buzz ) but if not adjusted properly it produces a loud hum instead. I just had to readjust the metal tab on the last one I worked on when alarm was going off to produce the intended buzz instead.

As for knob.. if it is a clear one you will need to find a donor. Could use the more available white until you find OEM


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 Post subject: Re: Dumont 1120 Clock Radio repair
PostPosted: Nov Sat 06, 2021 8:59 pm 
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Joined: Aug Tue 10, 2021 9:49 pm
Posts: 63
Location: Chesapeake, VA
Thanks, dacsman. Do you have any suggested websites as to where I could find a white one? The post is more of a blade.


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 Post subject: Re: Dumont 1120 Clock Radio repair
PostPosted: Nov Sat 06, 2021 9:26 pm 
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Joined: Dec Thu 10, 2015 7:01 pm
Posts: 569
Location: Aurora, IL
Guess I didn't look close enough at style other than to notice it was clear plastic. Do a search on ebay for clock radio knob.. you'll find a good assortment. Some may be exact replacement you are looking for although some are very pricey.

Edit: Looking at photo of clock dial I realize yours does not have the typical 1/8" round split shaft typically seen on this eras clock radio but looks like a flat shaft. If that is the case you would need to make sure your replacement knob is for flat shaft.


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