Too bad this DuMont's not a tabletop
 

1949? I don't know DuMonts, and references are spotty.

With the small screen, I'm not sure it merits that much floor space. Guess it has a good sized speaker. Apart from that, is the audio section any better than most TVs of the time?

Phil

If that's an RA-103, it has a real F/S discriminator, and one stage of limiting, a 6SJ7 1st audio, and a 6V6 output, at least that's what's in my doghouse. Average. But it could have a different amp seperate from the chassis.

BTW Phil, Thank You for posting the info on the RCA 8" personal portables. It was invaluable to me when I did mine!
Kevin

Nice set but why is the tube off center?
It looks like it could be a 15".

Are you thinking of getting it? :yes:

Got a saw? :scratch2:

Seriously, Has anybody here ever converted a floor model to a table model rather than pass up a desirable set due to space restrictions in the "TV room" ? I never have, but have thought about a couple of times.


jr

Hmm, if you cut it down it wouldn't be very desirable any more. :no::D

Well, I'm thinking of going to look at it. Price is OK, but it's missing the knobs, the picture tube is loose (taken out for moving and not reattached), has a chip of veneer missing, and . . . it's big. I wouldn't cut it down, so I'd have to want it enough to have it in that cabinet. It's not like you can just run down to Target and get all those knobs.

On the plus side, it's a DuMont. I wouldn't mind getting out of my RCA rut.

Phil

Looks like an RA-105 with a 15AP4, or 15DP4 CRT. I sure do miss mine, having to give it away when my parents sold their house last year.

Hope you get it, Phil!
See ya,
Matt Davala

It's a 12" set. Relative to the chassis, the 15" tubes are always positioned somewhat high and further to the left.

So, same chassis as a Doghouse? Control layout looks the same except that this eye's directly above the tuner.

Phil

I was feeling smug about escaping my RCA rut today until I spied Dave's $50 621TS and broke into tears for some unknown reason. Still, for $40 and a 5-minute drive, I shouldn't gripe.

Also included: RA-103 service sheets and a box with about two dozen tubes. The cabinet has a loose, warped top, and some other boo-boos, but nothing I haven't dealt with before.

Check out the ginormous box cap strapped to the top of the HV cage. The "repairman" wired it in parallel with one of the p-s filters. :nono: Something mysterious happened inside one of the 5U4G rectifers, but there are two more in the spares box.

Won't be trying this out any time soon. It's #4 in the project queue.

Anyone know the name of this cabinet? Oh, I need a complete set of knobs, too.

Later . . .

Phil

Good save. That one is the "Meadowbrook". $525.00 in 1948.

Nice score :thmbsp:
Interesting. That chassis looks just like the one in my Crosley 9-407M

Indeed! GREAT FIND! :thmbsp:

They look identical to me...Anybody know the story? Did DuMont (or Crosley) build them both?

jr

EDIT... found this thread:

http://www.antiqueradios.com/forums/...er=asc&start=0

jr

I like the styling. It really gives you a feeling for the period.

John

Nice, I think you'll find that chassis is very easy to work on, lots of room.

Wonder what that big capacitor on top of the high voltage cage is for?

Thanks for the thread link - great read.
Phil and I will be able to compare notes on this restoration :yes:

Yah, that Crosley chassis does look like the same, from what I can see. Interesting.

The huge can on the HV cage must be an electrolytic, although I've never seen one that size, and the markings on it give no clue. I spoke too quickly before; it's wired in place of one of the filter caps, not paralleled with it.

I'm itchin' to start playing with it, but I forced myself to stick it back in the cabinet and wheel it off to the side until I finish other things. I do like that cabinet style, now that it's home.

That antiqueradios thread is a real textbook. Let's hope I don't find problems like a broken Inductuner shaft!

Phil

That looks like an oil filled capacitor to me.

John

Nice set. Ever since I got my first Dumont, I've been looking for more....
http://farm4.static.flickr.com/3445/...b29745c7_b.jpg

Mine is a '49 also.

MK

DuMont is the KING of power transformers! I remember my old RA-109A had this crazy thing that looked as big around as this one, but twice as tall. Wow! Dual LV rectifiers and all. I wonder if the HV rectifiers are dual. Mine were, but the 109 is a far different chassis.

That transformer is a serious piece of iron. About six inches tall. I have a special machine for moving these heavy chassis. It's called my 23-year old son :)

On this chassis I spy two 5U4Gs and one 5V4 by the HV cage. Not sure if I have the right papers for this set. The crumpled schematic lists RA-103/104A/110A and shows two 5U4gs and two 6X4s. Eventually, I should get the right schematic. The serial plate in back says RA-103, serial #27171.

I'd love to get knobs for this set. The seller told me they were all lost, but last night I went through the box of spare tubes (39 good ones --Yay!) and found this one. So I need four more like this, plus the big tuner knob.

Phil

I have the complete DuMont schematics, alignment and parts lists for RA-101 through RA-171. They list RA-103D, 104A and 110A as the same schematic so that's probably the one for your set.

Dang, change of plan. My wife put her foot down about "more ugly black and white TVs," so I slopped some Howard's on the cabinet and did a color conversion. Maybe I'll get used to it. At least it was worth a good laugh watching the trashman try to lift that useless old chassis from the curb!

(Just joshin' -- I was sorting a bunch of photos and just couldn't resist.)

:)

:lmao:
You really had me going there. I was getting all ready to write a really nasty response :)

Today I got a Sams (Set 93, Folder 4) from the library. It lists those models -- RA-103D, RA-104A, RA-110A.

Mine doesn't match. Sams shows a little sub-chassis with two 6X4 tubes, sticking up from the main chassis by the power transformer. Nothing like that on mine, and no evidence there ever was such a critter.

The serial plate just says RA-103-. No D or other letter. Serial # 27171.

?

Phil

I did an RA-103 "Chatham", in superb cosmetic condition, a few months back.

You'll have little problem with it, is my guess. It's a LOT less complicated than the 630TS.

Mine works great. A little quirky with Sound synching up to Video when first switched on, but, it settles down when warmed up.

My RA-105B "Sussex" is my most trouble-free vintage TV. I switch it on, and Picture and Sound are Rock-On. No tweaking needed, ever.

LJB:smoke:

Here's a partial schematic of a RA-103 C. Does it match?

http://www.bobandersen.com/images/sc...103%20C-01.jpg

That looks more like it, without 6X4s. Looking at my crumpled sheets, I have a page 13 from what looks like the same book, with schematic for RA-103D & others mentioned before. I also have pages 10, 11, and 12, labeled RA-103C. If the one you scanned is page 9, that may be the missing link.

I wonder if this set is in Riders . . . ?

Phil

Yep, I scanned page 9. Pages 9-12 are RA-103C from DuMont Television Service Data 1953.

Either I'm nuts or this guy knows something that I don't. I started on the power supply filter caps for my RA-103. This TV had the big box cap (10mfd/600v) strapped to the top of the high voltage cage.

It looks like he took the two 80mfd filters, C262 and C241, out of circuit, along with the 100K resistors R316 & R317, and subbed this 10mfd cap.

In the photo, C241 is above C262. The long blue and red leads came from the box cap. So that cap was wired between the positive of C262 and negative of C241. The resistors are nowhere to be seen; perhaps they were originally mounted on the cans.

I'll put everything back as per the schematic, of course. Just wondering whether this scheme actually worked. That was a big honking (possibly nonpolarized?) cap in that box, despite the low capacitance value.

(Don't ask me to fire it up with that thing in place just to see what happens. The answer is No :) )

Phil Nelson

I bet it worked ok ... the two 80s were in series with equalizer resistors across each one to keep the voltage on both caps approx equal. The two 80s in series would add up to one 40 with twice the voltage rating. Substituting a 10 for the 40 would result in increased "hum", but perhaps not terrible.

jr

I wondered why they used two caps in series in the first place, when a single 40 would do. Over-engineering for longevity? Parts cost/availability?

Phil

I suspect that that point might hit over 500V before the other tubes in the set warm up and start drawing current, so two 350V caps in series would provide a 700V rating. I don't think that 600 or 700V electrolytics were available. I think that to a certain extent, Dumont over engineered the design, to promote longevity. Since the set was likely quite well filtered, replacing the "40" with a 10 probably worked ok, perhaps introducing only a slight amount of hum. The ESR of the 10 was likely less than the two 80s in series, as well.

jr

Speaking of over-engineering, the TV has a time delay circuit to reduce surge. See the 6AL5 tube, V224, and K201 in the schematic.

From the service manual:

The relay circuit has been designed so that the relay is energized approximately ten seconds after the power is applied to the television receiver. In this way all capacitors and other components are protected from the high surge voltage which otherwise would occur before the tubes heated up and started to draw plate current.

Some of my later sets use a thermistor, instead. Maybe they didn't exist when this was designed (?).

Phil

Phil, that relay will have an open coil as often as not.
There's a modern relay that can be cannibalized for the 5000 ohm coil if needed.

WOW! I did not spot that... a 10 second delay should take care of *most* of the surge. These folks were serious ! :yes:

jr

I guess the relay's OK. Replaced four caps in the p-s and brought it up on the variac. Makes a dandy FM radio, with nice bright magic eye. TV audio is fine, too. Picture has some issues, but hey -- it's only 5% restored :)

Phil

Well you know it's the last 5% that's hard to get right. :D

Tell me about it. I think I have earned a gold membership card in the Ninety-Five Percenters club.

Phil

39 caps later, percentages are looking up.

Phil