Dumont RA-103D "Rumson" restoration
 

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 :no:

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

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Chassis is filthy but doesn't look too bad from the topside.
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Some good news - the tuner ceramic shaft appears to be intact.
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The original 12QP4 CRT was so dirty I thought it had a dag coating at first!
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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.
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Here's a test fitting.
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Now what you've all been waiting for - the underside.
Doesn't look too bad - right?

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Let's dig deeper.
First off, something very bad happened in this corner.
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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?
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Next up, the B+ delay relay is shot and has been jammed closed.
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and the linearity coil is open. Mice gnawed on a few of the wires too.
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and broken terminal strip lugs. Also, several broken tube socket lugs.
Basically, wherever work was done, there is damage.
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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.

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?

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It's cleaning up well. May seem silly to some, but I hate working on a filthy chassis.
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While I had the CRT out, I replaced the short electrolytic cans hiding underneath.
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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.
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Also, start recapping underneath. Funny to find the video detector tube hiding down here along with several "gimmick" capacitors.

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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.

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.
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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.

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

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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.
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Thanks to a parts chassis, now I know there should be another candohm down there.
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One of these things is not like the others :no:
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I just happened to have a 50W, 1.2K resistor handy. Original was 1.25K @ 25W. Now to sort out the wiring
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At least the ceramic inductuner shaft is unbroken.
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A 100 q-tips later
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I've found on the coils it's easier to grab a large white block pencil eraser and some De-Ox-Id contact cleaner spritz the eraser and use the eraser to scrub the tarnish off them while rotating them spritz the coils and wipe them off with paper towels. I pull out the slider contacts and wipe the contact patches on them clean on the eraser (a new one with sharp corners will get into the coil groove).

i told you a million times not to exaggerate!! :nono::D

Is it just the photo, or is that 12LP4 aluminized? 12KP4??

No, it's not aluminized.

How did you get that tuner cover off? It has small phillips head screws behind the RF towers and I can't get to them.

Lee:smoke:

Needle nose pliers and patience

Ah. No easy way. Just like when I cleaned up an RA-105B tuner 20 years ago.

Lee:smoke:

Who's up for a challenge? Speaker cone is trashed and output transformer primary is open.

New cone has been ordered and I dug up a transformer I think will work. At least it's the same size and has continuity.
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Meanwhile, I patched the set up enough to try a full power up. Relay is still bypassed and power resistor just tacked in place.
Need to dig up a new eye tube too.

Also, discovered the flyback is a replacement and not secured very well.

Replaced HV cable with more convention HV cup and rigged up a 5AXP4.

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After a few pops and cracks that made me jump, we have a raster!
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A lot of control fiddling later, we have an image. Tuner seems to be off by a couple channels.
I'm both surprised and relieved this set actually produces an image after all it's been through.
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Some tube swapping and more control twiddling and we have a decent image.
Mind you I have no shields installed and am feeding a signal in with alligator clips.
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One thing you can do is remove the IIRC 4 Philips screws under chassis that hold the tuner to the chassis and with the tuner loose you can get to those screws....I will add the caveat that Ive never owned a square dial 103 (only both versions of the round dial) so I don't know if the square dial tuners allow you to do this as easily. I've had at least 3 RA-103 tuners off in the something like half dozen RA-103s I've benched. Two were to swap when I was making a good chassis out of 2 mouse eaten ones, and the other was to deal with a snowy picture issue...That one it turned out that a mica in the lower compartment of the tuner that coupled the antenna to the RF amp had a snapped off lead at the cap body.

Just about done, but have one annoying issue.
The dial scale is off and I can't tune below channel 4!
Now the cam kicks in at the right spot where it spreads out the FM radio portion but LO is off.

Closer examination revealed that when I am tuned as low as it will go, there are still a couple turns left on the coil.
When I'm at the top of the dial, the coil is nearly at the opposite end.

It seems like I need to bump all three coils over one turn.

Is that even possible and, if so, how? Short of taking it apart that is.
Is there a way to adjust the mechanical stop?
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It sure looks like one could tweak C23 to shift the LO. Not sure if I can get at it easily or if that would also require tweaking C16 and C17 to track properly.
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Bob, if you have full shaft rotational travel stop to stop, just pop out all 3 sliding contact fingers (one under each coil) and reinstall them on the end winding. Just push them out from the side with a small screwdriver. I always pop them out to clean them. One coil is reverse spiral so one contact goes in on the opposite end from the other 3.

Yikes. Do they really come out that easily? That big IF can will make one section extra tricky.
Before I attempt, I want to double check reception at the upper end of the dial.

Yes, upper end also off by about two channels. Ok I'll give it a try

Well, down the rabbit hole we go...

I removed the stop and turned one more rotation towards the low end and it's now cleaned and lubed.
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So, the rollers are all shifted over one rotation now. Did it solve the problem? Sort of.
Yes, I can receive 3 and 4 now, but 3 is smeared over a big range. I think I need to adjust the cam behind the dial that alters the action through the FM band. Upper VHF reception seems a bit degraded but the goal to get clean 3 & 4 has been achieved.

Also went down to my storage space and pulled a nice speaker out a Stromberg Carlson clone. Also, a 6AL7, but it's very dim.

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Does anyone know what position the cam (arrow) should be in when installing the dial mechanism? I have the tuner fully counter-clockwise and have tried with arrow straight up but that's quite right.

I believe it should spread the action out through the FM radio portion.

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The RA-103D has four Phillips screws below the tuner.

Good.

Lee

Perhaps line the arrow on the cam up with that small pointer below the rivet on the arm with the pulley.

After screwing around, I got it working well enough. Did not discover any magic alignment point. Just a lot of trial and error.

Also picked up a NOS 6AL7 - much better.
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Then I installed a strong, used 12LP4.
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Time for reassembly. The weight of that transformer has a taken a toll on the cabinet.

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The cabinet had been painted white in the distant past then stripped and refinished by someone else.

Was very crunched for time so don't have any photos of it playing in the cabinet.
No worries - I have three more RA-103 based sets coming up :drool:

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I really appreciate the time and effort you put into this, posting videos so those of us who are TV repair novices can have practical, hands-on instruction. Having a good text on hand is nice, but watching someone do it in real time is invaluable. It seems to me that finding parts is the big deal when you work on this old stuff. You make it look so easy.....

Thanks. This model is especially troublesome with the focus control and relay often being bad.