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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Tue 05, 2019 7:39 pm 
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Location: Ann Arbor, MI
How did you get the cabinet refinished? Did the white paint come off cleanly?

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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Tue 05, 2019 7:47 pm 
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I got a professional to do it. This is a fellow who restores antiques. He came to my house, made suggestions, and then picked it up and returned it about four weeks later. Interestingly when he removed the white paint he found black paint underneath, although that could have been a primer.
I had decals made, and he applied them.
Thanks.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Wed 06, 2019 2:06 am 
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Did he manage to save the photo finish?

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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Wed 06, 2019 2:14 am 
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Tom, No, he did not.
I reviewed the "photo finish" topic from this forum. He told me his removal process would take everything off. But, it came out so nice, I wasn't disappointed.
This had gone from my wife saying "Get that out of here," to "This is a nice piece of furniture." She's seen pictures of original TVs with what I guess is the original finish.
I'm currently trying to figure out how to remove the "sparkles," which I understand are noise, and which aren't present when I play back DVDs. I'm probably going to try a new HD/Analogue converter, and maybe a shielded cable. I can't figure out what's causing it.
Thanks for asking.
Randy


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Wed 06, 2019 5:21 am 
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Location: WI 54812
You could also try another 75 ohm to 300 ohm antenna transformer. I've had those go flaky and pick up interference.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Wed 06, 2019 4:07 pm 
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Many DuMonts had a coax from the tuner to the antenna terminals...That coax was typically 72ohms IIRC....so using a 75 to 300 ohm matching transformer actually makes the match worse....in those sets what you want to do is take a modern 75ohm coax lead, cut one ends connector off strip the leads and hook them to the antenna terminals in the same manner as the tuner coax lead is. That or get an RCA to F type adapter (IIRC some sets used an RCA antenna connection instead of screw terminals).

May want to check for HV arcing and if it has an all glass CRT if the aquadag is grounded to chassis. Sparkly interference like that is typically from arcing either in the set of in a brush type motor within a few hundred feet of the set...Some modern switch mode supplies (which are in everything from non-incandescent bulbs to microwaves and computer power supplies these days) can do that too.... having a cheapie 2000's 5" monochrome portable CRT set to walk around and do interference checks with is good.
May also want to switch your modulator from ch3 to 4 or vice-versa...with the current ATSC3.0 channel repack there are more and more DTV RF carriers on VHF and those will interfere with any analog application on that channel.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Fri 08, 2019 3:18 pm 
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Thanks. I'm trying a new set top box first. I've ordered one.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Sun 10, 2019 9:24 pm 
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I hooked up a new settop box. Some of the sparkling still exists. But......
Just for fun I connected a cable from the Video Out of the setup box to the Video on the Dumont. (Yes, the Dumont has a female RCA jack labeled Video, and another one labeled Phono.) The sparkles went away. Still a lot of sound noise though.
Here's my question/problem. The Dumont Video In doesn't seem to do anything. As long as the setup box is connected to the Antenna, there's a picture, with our without the Video connection. So, is there a way to have the Dumont display video from the Video In? Or did I just luck out when I added the settop box video connection?
Thanks.
Rand


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Sun 10, 2019 11:11 pm 
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rb462@aol.com wrote:
I hooked up a new settop box. Some of the sparkling still exists. But......
Just for fun I connected a cable from the Video Out of the setup box to the Video on the Dumont. (Yes, the Dumont has a female RCA jack labeled Video, and another one labeled Phono.) The sparkles went away. Still a lot of sound noise though.
Here's my question/problem. The Dumont Video In doesn't seem to do anything. As long as the setup box is connected to the Antenna, there's a picture, with our without the Video connection. So, is there a way to have the Dumont display video from the Video In? Or did I just luck out when I added the settop box video connection?
Thanks.
Rand


Although I've never seen reference to that video jack in Riders or Sams service info, I've traced the wire to a capacitor that's in series to pin 7 of the Video Amp tube. Pin 7 being the cathode, so that jack would have to be considered a low impedance video output. Interesting that it's on some sets and not others, and no one seems to know what it was originally intended for. The reason for the connection resolving your sparkles is that possibly the cable shield is offering an alternate grounding path to the set top box.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Sun 10, 2019 11:36 pm 
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Oh! So the jack is actually an output? But the phone jack is an input? Interesting.
Thank you very much for tracing this.
I guess I'm at a point where the sparkles are resolved, and I call this success?
One interesting thing: I bought a new settop box, and it doesn't work as well as the old one. For some reason, I get more "No Signal" screen messages, even though I'm using the same antenna, which, I think is the original 1952 antenna that came with the set. I'm not convinced that buying an HDTV antenna would improve the picture.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Mon 11, 2019 1:09 am 
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rb462@aol.com wrote:
Oh! So the jack is actually an output? But the phone jack is an input? Interesting.

Yes. Consider that back in 1950 no consumer would have had a video source to plug into that jack. For that matter I don't know what use the output would have been. Oh, one other thing. I'm not sure if running the DuMont video out signal into the set top box is going to do the box any harm, but maybe try running a single wire from the chassis of the TV to the that of the set top box. If a single wire doesn't have the same effect on the sparkles, I'm at a loss as to what's going on. Probably something magical. 8)


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Mon 11, 2019 1:23 am 
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Perhaps it was meant to supply a video signal to a color wheel demodulator?

-Steve

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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Mon 11, 2019 2:03 am 
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azenithnut wrote:
Perhaps it was meant to supply a video signal to a color wheel demodulator?

-Steve


That very well could be.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Tue 12, 2019 1:17 pm 
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Now, all of a sudden, the sparkles are back. I didn't change anything, though.
And, sometimes, the picture sort of freezes.
With all this, I still love the set. In fact, I'd like to get a tabletop set from the same era and have it restored.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Tue 12, 2019 2:00 pm 
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The freezing is entirely within the set top converter box.

Does your old box have a video out?

Sometimes a poor connection in the shield of the cable between the box and the TV can cause sparkles and interference.
Try replacing that cable and make sure the connections are solid.

-Steve

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-Zenith
-Sparton
-Pre-War FM
Consoles and floor models, the bigger, the better!


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Tue 12, 2019 8:45 pm 
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Go to your local thrift stores and look for a VCR/DVD combo player from the 90's that usually has a selectable channel 3 or 4 RF output. They should be inexpensive and you can compare that signal source to your set top box. Besides being able to watch DVD's of old movies, they make a very handy piece of test equipment because you can play a DVD with test patterns on it.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Wed 13, 2019 12:08 am 
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Actually, I’ve already done that. The picture from the DVD output has none of the noise. And, you’re right, it is neat to be able to watch ad Sullivan on a black-and-white TV. But I still don’t know what’s causing the picture noise from the converter box. Or, maybe it’s coming from the antenna.


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 Post subject: Re: Dumont Tarrytown RA-113?
PostPosted: Nov Wed 13, 2019 4:28 pm 
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If your VCR/DVD unit has audio/video inputs you can connect the a/v outputs of your converter box to your VCR, select the A/V input channel on the VCR and DTV will pass through the VCRs RF modulator....As an added bonus you may be able to record DTV that way too.


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