Dumont RA-103D "Rumson" restoration - Videokarma.org TV - Video

bandersen · #1 09-02-2023, 03:00 PM

I've been slowly working on this set the last few months and it's turning out to be a real challenge.

I forgot to take any good photos before getting started so let me fill you in a little. The owner found this on the East coast in rough condition.
It had been painted pink, was missing the back, had a brightener and as I was about to discover, real ugly old repairs/hacks.

His brother did a nice job refinishing it, but the knobs retain some of that pink

I think the dial glass broke in transit to my place. Should be easy to replace.

Chassis is filthy but doesn't look too bad from the topside.

bandersen · #2 09-02-2023, 03:07 PM

Some good news - the tuner ceramic shaft appears to be intact.

The original 12QP4 CRT was so dirty I thought it had a dag coating at first!

I tested very weak but I was able to rejuv enough to get into the green. Life test and cutoff are pretty bad though. We've already discussed replacing it with a strong 12LP4. It's slight longer and has a different HV cap, but I think it will work.

Here's a test fitting.

bandersen · #3 09-02-2023, 03:17 PM

Now what you've all been waiting for - the underside.
Doesn't look too bad - right?

Let's dig deeper.
First off, something very bad happened in this corner.

Seems the focus rheostat burned up and was "replaced" with a fixed power resistor.
Some of the connections were just twisted together. Wonder how well it worked?

bandersen · #4 09-02-2023, 03:32 PM

Next up, the B+ delay relay is shot and has been jammed closed.

and the linearity coil is open. Mice gnawed on a few of the wires too.

and broken terminal strip lugs. Also, several broken tube socket lugs.
Basically, wherever work was done, there is damage.

kvflyer · #5 09-03-2023, 02:13 PM

Quote:

Originally Posted by bandersen

Basically, wherever work was done, there is damage.
...

Bob, that's a shame. I will admit to damaging terminal strips and tube sockets a few times in my "early years" of restoration. But lately, I have a lot of patience and very, very carefully remove all of the old wire from the component. In the last set that I worked on, many times I would have to unwind two or three components which were wrapped on top of the wire that I needed to replace. If it were resistors (often) they usually got replaced unless they were spot on value. I don't think that there is a value that I don't have now. I have been collecting them for quite some time.

Anyway, sorry to blabber in your thread. I look forward to following this.

bandersen · #6 09-03-2023, 07:30 PM

Pulled the rectifier tubes and power it up. Poer transformer seems to be fine.
Was surprised to discover the vertical tower in the back with 6X4 sticking out is the negative bias power supply. I'm guessing this was added on in later revisions?

It's cleaning up well. May seem silly to some, but I hate working on a filthy chassis.

While I had the CRT out, I replaced the short electrolytic cans hiding underneath.

I used adapt-a-caps. Although the originals were twist-loc, there were already holes in the chassis in the right spot for phenolic insulated types.

bandersen · #7 09-03-2023, 07:35 PM

Also, start recapping underneath. Funny to find the video detector tube hiding down here along with several "gimmick" capacitors.

Electronic M · #8 09-03-2023, 09:07 PM

The 6X4 tower was a later revision. The doghouse RA-103 sets lack it.

The tuner shafts typically don't break on the square dials, and half of the round dials....Some of the round dials (I think the early ones) had the tuner shafts come straight out to the knob and lateral forces on the knob tend to snap the ceramic. Later round dials and the rectangular dial sets have a separate knob shaft that drives the tuner shaft through gears and those sets usually don't suffer shaft breakage. The later and earlier round dials actually have the dial spiral silk screened to rotate opposite directions and thus are not compatible....I need the dial scales for a later RA-103 round dial.

bandersen · #9 09-03-2023, 10:03 PM

Thank you for clearing that up.
I do have a Stromberg Carlson TV-12 clone wit no bias tower and direct drive with a broken shaft.

Electronic M · #10 09-04-2023, 02:31 PM

Quote:

Originally Posted by bandersen

Thank you for clearing that up.
I do have a Stromberg Carlson TV-12 clone wit no bias tower and direct drive with a broken shaft.

You're welcome. I've got a S-C TV-10 (a TV-12 with a smaller inner mask, a 10BP4 and a block of wood as a spacer), and a RA-103 doghouse and the only difference besides the cabinet is that S-C painted and paint stamped over a bunch of Dumont part numbers on transformers.

bandersen · #11 08-26-2024, 11:17 AM

Finally, back on the Rumson. I tracked down a replacement relay, focus control, hor. linearity coil, power resistors and tube sockets!

Every single power candohm section is open! This is just temporary until the chassis mounted resistors arrive.
I suspected something very bad had happen down here going by the chared residue and hack repairs.

Thanks to a parts chassis, now I know there should be another candohm down there.

One of these things is not like the others