Dumont RA-104

[Radiotronman]

I've been looking for a Dumont tv for a long time and one finally appeared before me. A friend I restored a Predicta for told me he had a friend with tvs and radios and wanted some restored. I contacted him and after talking awhile, he told me he had a Dumont Wellington, model RA-104. I really wanted a round CRT Dumont, but I'd take any Dumont I could find. This set has the 15DP4 CRT and seperate am radio chassis too. It's cabinet is in great condition with only a few small scratches. It also has the three speed record player. To say I'm excited to have this is an understatement. I've got several projects for people lined up ahead of it, but can't wait to get to this fine day! The picture is after I got it home with all chassis removed.

[Radiotronman]

Here is the cabinet with the doors closed. It is a very well made cabinet and very heavy, without the chassis in it.

[DavGoodlin]

Originally Posted by Radiotronman

Here is the cabinet with the doors closed. It is a very well made cabinet and very heavy, without the chassis in it.

My RA-105 Sussex is pretty close in heaviness. Be careful moving yours. I broke my CRT - it was unsecured on its crane rail and slid out as I lifted it off my truck. Another V-K member has a complete RA-105 but its in Wisconsin. I would buy the entire set just for the CRT. I also have an RA-103 Savoy parts set but sold the CRT to another V-K'er for his doghouse.

[Radiotronman]

I checked the CRT to see if it is good, even though I was told it was. It came way up into the green on my tester. I put the multiple chassis back into the cabinet and put the knobs on until I'm ready to begin restoration on it.

[Radiotronman]

While I was looking at my Dumont and cleaning tubes, I noticed this wood bracket at the bottom with a few screws. Nothing seems to be missing on the chassis. Was this a mount for some kind of aerial antenna or what?

[Tim]

During shipment from the factory, the yoke and focus coil assembly were fastened there in order to relieve stress on the neck of the CRT while shipping. When delivered to the customer, the installer would remove them, install over the neck of the crt and make final adjustments.

[Radiotronman]

Interesting, that makes sense, thanks!

[Radiotronman]

Just ordered my focus potentiometer to replace the one on my set. It's a 1k, 25 watt wirewound control. Surplus Sales of Nebraska had them for only $8. I also replaced the .05@1000v cap and the .035@1000 cap; since I had them on hand. I write down every cap I need to order, over 40 paper caps and 20+ electrolytics. Does anyone know what to replace the paper tubular caps in the chassis listed as 1.6 ohm caps? What are these? I've never seen them in sets before and what should I replace them with? They are like dyed on the sams as C4 and C5.

[Kevin Kuehn]

Shown on the schematic as polarized, so I suspect they are large mfd, low voltage electrolytic type? Apparently 1.5 ohms is their impedance at 120 hz. Using the below calculator I came up with 880 mfd to get close to 1.5 ohms. Looking at that Aerovox part number(PRS6/1000) I'm going to guess they're 1000 mfd @ 6v. I'll see if I can find that AV number in an old catalog.

http://www.allaboutcircuits.com/tool...ce-calculator/

[Kevin Kuehn]

Here's a Radio Master listing for those Aerovox PRS series. Oddly they don't list the complete part numbers. Maybe check and see if the 1000 mfd @ 6v fits the physical dimensions of what's in there.

[Electronic M]

IIRC the 104 is similar to the RA-103...I have a Stromberg-Carlson TV-12 chassis set that is a rebadged Dumont RA-103.....In the Stromberg's sam's that is on the ETF schematics page it lists the capacitance and voltage of those lytics...They are low voltage (IIRC 6 and 25V) high capacitance parts...You can easily find spares in junk SS gear.

[Radiotronman]

Great info guys. I wonder how critical the value is, given how high the capacitance they are?

[bandersen]

I wouldn't stray too far from the stated values. These are usually used on the centering controls with 1,000uF for the vertical and 250uF on the horizontal. You really don't want any hum or the image will ripple.

[Kevin Kuehn]

Interestingly if you look at C6 on the Sams parts list(vertical bypass), they actually listed that one as 2000 mfd @ 6v. Probably DuMont overkill?

[bandersen]

I've done sets with 2,000uF too. Motorola and a Sentinal IIRC. 2200 uF works just fine for replacing those.