View Full Version : Dumont RA-109-A3


EdKozk2
03-07-2017, 07:32 AM
My son and picked up a Dumont RA-109-A3 "Sherbrooke" yesterday. We drove out to Platteville, WI to get it. It was listed on craigslist. We carried it home on my car's DIY roof rack. We pulled the chassis and broken crt before we lifted the cabinet. I didn't realize how heavy Dumonts are. The set is missing the speaker/output transformer, some knobs, phono cartridge and the back cover. The 19AP4 crt was cracked open under the tube base, useless.
Does any one have a picture of the back cover of this set?
Ed

Kevin Kuehn
03-07-2017, 12:27 PM
Ed,

Your back is probably very similar to my Westbury. My 19AP4 is dead too. Some day I may just have to sub in a 17BP4 or such. I may have few spare knobs around here some place.

http://i452.photobucket.com/albums/qq245/Kuehn/VK%20Pictures/DuMont%20RA-109%20Back%20001_zps2aw5yjlu.jpg

EdKozk2
03-07-2017, 01:03 PM
Thanks for posting the picture Kevin. I'll post a few pictures of the cabinet/ knobs in a day or two.

EdKozk2
11-17-2017, 11:12 PM
Well, I finally got to recapping this set a few weeks ago. I purchased a used 19AP4c CRT from the ETF this last summer. I still have to test and repair the phonograph yet.
Ed

IsthmusTV
11-18-2017, 11:33 AM
Nice work, Ed! There's nothing like a DuMont :yes:

-Clark

Electronic M
11-18-2017, 12:05 PM
That is a real good picture on that set.

Phil Nelson
11-18-2017, 05:51 PM
Nice work! Those early DuMonts are my favorites.

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html

Kevin Kuehn
11-18-2017, 05:56 PM
I like it. :thmbsp:

EdKozk2
12-12-2017, 02:10 AM
Thanks for all the kind replies.
Has anyone who ever repaired or restored a Dumont with the ferro-resonant power transformer ? The transformer on this set hums louder than any television I've repaired. It's only the transformer, no hum in the picture or sound. The transformer also gets hot too hot to touch after a couple of hour in operation.
Could a leaky 1.75 - 2.0 mfd 800vac (yellow dot) cause the excessive transformer hum and heating ? The cap is connected accross the 800 vac secondary winding.
Ed

bandersen
12-12-2017, 10:29 AM
Ferro-resonant power transformers do tend to run hotter and noisier, but it does sound like yours isn't working right. That cap forms a resonant tank circuit and is critical to the proper operation of the transformer.

Kevin Kuehn
12-12-2017, 02:20 PM
That cap is a dead short in my Westbury. I think others have found them bad too. I'm not sure what could be use as a replacement, but possibly a few 1000v metalized films in parallel. I wonder if you could hear the difference if you fine tune the value?

Electronic M
12-12-2017, 02:53 PM
I agree with Bob. I've never owned a Dumont with that trans, but I have owned a few VRT equipped SS Zeniths as well as some line isolation VRTs. They work best with a substantial load, and when loaded run on the hot side, but too hot to touch sounds wrong.

The caps used by these are typically motor run AC can type (paper in oil non-polarized IIRC). Look for the AC voltage rating of the original, and match capacitance as best you can in a replacement.

Tom9589
12-12-2017, 04:55 PM
I find it interesting that the Sams for this set doesn't even list a Dumont part number for this capacitor, much less part numbers from other capacitor manufacturers.

Could it have come with the power transformer?

EdKozk2
12-12-2017, 05:08 PM
Thanks for the responses. After the holidays I'll pull the chassis, yoke, and focus coil and test the set with another cap. I may try your suggestion also Kevin, I have some 1uF 460VAC caps I could combine.
Ed

Kevin Kuehn
12-13-2017, 07:41 PM
Do you guys feel this application needs an AC motor run type(film in oil) in order to effectively dissipate heat? I was planning to try AC rated film caps and see how warm they get. If not too bad I was then going to try re-stuffing the original can.

EdKozk2
12-13-2017, 09:41 PM
I find it interesting that the Sams for this set doesn't even list a Dumont part number for this capacitor, much less part numbers from other capacitor manufacturers.

Could it have come with the power transformer?

Hi Tom9589,
The transformer was made by SOLAR and the oil filled caps were matched to the transformer. That's why I mentioned the yellow dot color code, which is painted on the transformer and cap. I've been operating the set with the original oil cap so far.
Ed

EdKozk2
12-13-2017, 09:51 PM
Do you guys feel this application needs an AC motor run type(film in oil) in order to effectively dissipate heat? I was planning to try AC rated film caps and see how warm they get. If not too bad I was then going to try re-stuffing the original can.

Hi Kevin,
I would give it a try and let us know how it works. A while back I tested a Zenith 95-3172 ferro-resonant transformer with film caps and it seemed to work fine. The Zenith was an early 70's color set.
Ed

Kevin Kuehn
12-13-2017, 10:01 PM
I didn't mean to imply I was going to get around to trying those caps any time soon. I can't start on yet another project until I finish the dozen or so others projects I have scattered about. :nono: :D

EdKozk2
12-13-2017, 10:41 PM
I didn't mean to imply I was going to get around to trying those caps any time soon. I can't start on yet another project until I finish the dozen or so others projects I have scattered about. :nono: :D

I hear you, I may catch up with my projects by 2040.:D

kramden66
12-19-2017, 11:57 AM
I had one of these sets , never replaced that cap ,mthey transformer was loud but didn't get hot , used it a lot and no issues , I think it is loud because it is big but that's just my opinion , those who have one can saw if the set they have is loud or wasn't after replacing thr cap.
Could it be replaced with an oil filled type used in transmitters ?

EdKozk2
12-19-2017, 01:39 PM
I had one of these sets , never replaced that cap ,mthey transformer was loud but didn't get hot , used it a lot and no issues , I think it is loud because it is big but that's just my opinion , those who have one can saw if the set they have is loud or wasn't after replacing thr cap.
Could it be replaced with an oil filled type used in transmitters ?

I suppose you could use any oil filled capacitor, as long all the specs are correct: 800 VAC or better, non - polarized, 1.75 to 2.00 mfd and the case is isolated. I think your correct about the hum being louder, but the amount of heat the transformer gives off after an hour and a half is what concerns me. The transformer has 39 filaments plus a few dial lights to operate.

Electronic M
12-19-2017, 07:51 PM
+b+