No. I cut them out and replaced them all, except for the one electrolytic I came up short on..I soldered it back in as a "placeholder" until I can get a new one today.

I did leave the aluminum cans in place, so I assume their "grounds" are still attached to the chassis. (Except for one that is attached to an insulating board which seems to have a separate ground as part of another circuit, C6 in the SAMS: Decoupling and Vert. Amp. Cathode, so it's ground is still connected to it's circuit) But the positive leads were cut loose and soldered to the positive leads of the new electrolytics.

Would there by any problems associated with that? Should I "gut" the old aluminum can caps?

The appearance of an old capacitor tells you basically nothing unless it has catastrophically exploded.

Caps may look perfect on the outside and be utterly worthless on the inside. Conversey, as ggregg noted, an old cap can also look awful on the outside -- all grungy, dripping, etc. -- and still be operational.

It's like finding a 60-year old car in the barn and trying to guess the condition of its engine by inspecting its paint job. Not a reliable guide :)

The failure rate for 60-year old electrolytic and paper capacitors is so high that you will save a lot of time and grief if you simply replace them all.

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

Howdy Phil!

So a cap with both ends bulged out can still be, technically, "good"?

Guess I should save those for spares! :lmao:

Photo of finished recap..except for the one electrolytic next to the transformer center-left, which is the one I came up short on because the SAMS parts list only indicates one 10uf 25 volt cap used. That one will be replaced later today, "Radio Shack be willing and the creeks don't rise". The other one is upper far right, normally covered by a metal box. It's tucked in behind the upper end of the yellow replacement cap up there. I put the one I had up there because it looked tough to get to, and it was, without a doubt, the most frustrating cap to install on the entire set so far.

If some of the electrolytic replacement looks a bit "ham-fisted", well, "c'est la vie", once the chassis is back in the set, I won't be able to see 'em, even from my house!

Lookin' good. I used to could see up close at a microscopic level back in my 20's, now I need to rely on a couple different strengths of reading glasses that I pick up at the grocery store.

Thanks! It's not as tidy as if I'd restuffed the cans and cardboard tubes, but there's a lot of room under that chassis for a lot of stuff.

I've been wearing specs since I was about 10 or earlier, but I used to be able to focus close up still wearing them. Over the last few years, that ability has just about disappeared. I've always been heavily "near sighted". Now, with my glasses on, I can see clearly from about a foot away to out as far out as I want, but things get blurry close up. I take my glasses off, and I can see crystal clear from about two inches out to about 6 inches out. There's an area between the 6 inch and one foot mark where I can't see ANYTHING clearly, with or without glasses, and that's where bifocals would come in.. call it vanity, but I'm resisting "old people glasses" as long as I possibly can! :cool:

Heh, I hear that. When I finally assented to trifocals I went home from the examination and found a letter in the mail from AARP.

fml :dunno:

I went with blended tri-focals.
I had the old style lined bi-focals, as safety glasses, years ago. They were nasty for night driving. It's bad enough, that you have to wear glasses. You might as well get glasses you don't mind wearing. :yes:

Finished up the recap job this eve, replacing the three 10000 volt caps in the HV section.

Reassembled, and powered up..no fire...no smoke..no buzz...no tubes glowing..no nothing....

Totally dead.

Did a bit of tracing of the power circuit through the on/off switch..and wouldn't it be a bummer if the set has been dead since around 1960 due to a bad power switch?

Well..the power switch IS bad. I jumped it and everything lit up on the bench. Still no explosions, no fire, no smoke, etc. But every tube lit up as it should.

Anyone have any luck repairing a power switch? If not, any idea where to get replacements? The switch is a combination on/off switch-volume control and hold control. I can solder in a temporary toggle switch for testing purposes.

I've posted a "Want Ad" with part numbers in the "Classifieds" section.

First, you have to determine what make of control it is. CTS, seems to be the most common. It could be Mallory, Clarostat, IRC or another East coast manufacturer.
Then, take the control all apart and transplant a known good switch.
One of the posters on this forum, could make up a control. IIRC, you sent them the defective control and they would repair or duplicate it. :thmbsp:

The one that is in there is marked "Centralab". I don't have any spares of any kind, so I'm going to have to locate a complete replacement. I would guess that an IRC switch won't fit on a Centralab control?

How could I forget "Centralab". They were on the Northeast side of Milwaukee.
I don't even think a CRL replacement switch would work. OEM and replacement parts, even from the same manufacturer, didn't interchange.
I'm only going by memory, as it's been ages. :sigh:

The SAMS photofact lists a "Concentrikit" by IRC, and lists a bunch of individual part numbers for individual components of the switch. Amazing how folks used to be able to repair stuff on that level!

I might try taking the switch apart and seeing if I can shoot some contact cleaner in there. It still "clicks" as if it's turning one and off...but apparently no internal contact. Don't have anything to lose since it doesn't work now.

I've found switches where the contacts are stuck open simply from setting too long and hardened grease. Sometimes a squirt of tuner cleaner/lube into the switch and cycling several times will free things up. One the other hand the contacts may be badly burned, in which case you'll need a replacement switch.

Edit - just seen you're already on the right track in you last post.

O.K., no luck trying to get the on/off switch to work, so I soldered in a jumper and am working the set off a switched power strip.

I remember saying early on that if I didn't get a TV out of this DuMont, at least I'd have a heck of a big old mono FM radio...and that's what I've got so far! :music:

I'm wondering though, since I've never seen this set do anything (including play FM radio, so I have made progress), exactly how is it supposed to act?

It has a three-position switch which switches from FM to TELEVISION to PHONO.

I'm getting FM radio on both the FM and TELEVISION settings, and when I switch to PHONO, the sound kicks off. On PHONO, I can plug in a phono cord and get a buzz if I touch the center conductor on the other end of the phono cord, so that seems to be working (I must have SOMETHING around here I can plug into that jack! Man, has technology changed! Curse you Optical Audio and HDMI!). On all settings, the heater filament in the picture tube glows. At no time, on any setting, does it sound like the picture tube is firing up..no static electricity sound, etc. No noise from the HV section.

I get a VERY dim eye tube, barely see it, but there is some action there while tuning through FM if I look close enough. Could be a wore out eye tube.

It appears I have a balky FOCUS control. When I turn that control, there is a "dead" spot in the middle where the sound drops out, but it picks up at either end, far left or far right. What the FOCUS has to do with that I have no idea at present.

My first though is that the FM/TELEVISION/PHONO switch isn't working correctly. Should I be getting FM sound on either TV or FM settings? Should the picture tube heater be lit at all times, on all settings? I would assume that switching to FM, the picture tube should shut off, but is that handled through the HV section alone?

Thank you for any thoughts/advice.

Cary, I believe you said this is your first TV, correct?

I also understand that you have neither substitute tubes, nor a tube checker, correct?

Next step is to dim your lights and verify that the plates on the 5U4 rectifier, the 6BG6 Horizontal Output, and the 6W4 Damper are not getting pink as this indicates something is badly wrong.

If any plates are glowing, turn the set off immediately.

Since you have not replaced any resistors, I assume that a resistance check will not be productive at the moment.

I cannot call the Sam's part numbers as the only schematic of the RA-112 is the Riders one at ETF which uses the factory numbers.

http://www.earlytelevision.org/tv_sc..._diagrams.html

However, I'm going to suggest that you measure all the resistance reading listed in Sam's from tube sockets, with the set unplugged. This will give practice for the next step and it might spot a pre-existing problem.

Make a Xerox of the two pages of Sam's and write down the resistance, at each point and color marking the ones that are off by more than 20%.

If no tube plates were getting too hot, your next step is to check the voltages that are shown in Sam's voltage chart.

Follow the same procedure of writing them down, again marking those 20% off in a different color.

James

Yes, you will get FM reception in both FM and TV positions and the CRT filament is lit at all times.
The only thing that happens in FM mode is that the CRT brightness is cut off. All the TV circuits are still running including the high voltage.
So you really are wearing out the TV tubes and CRT while just listening to the radio.

Check your schematic. Your B+ is fed through your wiper on the focus pot. I assume that is a wire wound. You might see if it is open in the center as that could be causing part of your problems.

I would be cautious about plugging in anything that uses transistors or chips into the record player jack, because this set has a semi-hot chassis though a 100 K resistor. Not enough to current there to hurt a person, but it might be terminal to a transistor circuit that was not buffered against a little AC.

James

I have a 15" RA103 or 104. It has the regular Dumont chassis, with the inputuner and FM radio. It also has a record changer and a AM radio chassis.
The strange part is the phono audio goes through the TV chassis. The radio is only used for AM radio reception. It's a six tube job, with a tuned RF stage.
Both chassis have a SE 6V6, output stage. The selector switch on the radio, cuts off the power to the TV chassis and switches the speaker to the radio chassis, when it's being used for AM reception.
I, personally, would have used the radio chassis for record reproduction.

Hey guys! Lookee what I found!

:thmbsp: :rockon: :yippy: :beer:

Howdy James!

Yes, this is my first set. I've done a couple tube radios, and a wind up phono (completely different tech!) The reason I've got this DuMont is because it's a family heirloom. I've run into some pretty good luck with it so far.It's nice to know it's history, and it's been in my possession for over 25 years, and I've been pretty protective of it.

As it started getting darker outside, I was able to look at the tubes as you suggested. No pink plates, so that was good. The darkness is also what led me to noticing that the CRT was apparently "coming back to life". I could see some VERY faint flickering, and started moving the ion trap around, and was able to brighten up the CRT immensely. I was pretty encouraged by that. Now I just have to figure out how to introduce a a signal so I have something to actually see.

We actually still have at least one UHF analog station broadcasting here..but alas, this DuMont has no UHF!

Thank you for the "system" for checking the resistors. I figure There's going to be some that need replacing. There's a LOT of them in there!

I do not have a tube checker. I've met a couple people who say they have one "somewhere", and say I can use it when they find it, but no one has dug one up yet. I'm starting to get enough tube driven stuff around here that buying a checker might be worthwhile. I do have a few extra tubes now. TV tubes are remarkably cheap, so buying them in lots is almost as cheap as buying one. I've got a couple 6J6's, 6BA6's, and several spare 6AU6's.

Thanks! Now I understand how it works, and now that the CRT is lit up, I see it's working just as you describe.

Now I'm no engineer, but "I am a thinker"..and it sure seems DuMont could have come up with a better setup than to have to power the entire TV, and wear out ALL the tubes (including CRT!) just to listen to the radio!

I've read of folks putting a circuit into their old radios with "eye tubes" that shuts off the eye tube a few seconds after tuning stops. I guess certain German radios did this right from the factory. With radio "eye tubes" getting scarce and expensive, I've thought about it for my '38 RCA console. I've read that useful life of a radio "eye tube", 6U5, 6E5, and the like, is around 1000 hours. Not very long if you listen to the radio a lot!

Just dreaming out loud here (figuratively speaking..errr...typing), but I wonder how hard it would be to unobtrusively install some sort of cutoff that kills the TV circuit..particularly CRT, when listening to the radio. TV tubes, in general, are plentiful and cheap..but CRT's sure aint!

It's always exciting to see that first light on the screen.

You may be close to having a coherent picture. What are you using as a source -- VHS player, DVD player, etc.?

As you may know, wherever your TV has two tubes of the same type (say, two 6AU6), you can swap them and see what happens. If no change, then chances are that they're either both bad or both good. In restoring dozens of radios and TVs, I've found that the majority of old tubes found in those sets were still good, so the odds are somewhat in your favor.

You can also perform a simple dud/not-dud test on a tube's filament with an ohmmeter as described at http://antiqueradio.org/FirstStepsInRestoration.htm .

I would not go nuts replacing marginal resistors at this stage. If one is WAY off or totally failed, then replace it, but consider that many parts of your TV are working "purty good" if you're seeing a lit screen. Going overboard with mass replacements creates more opportunities for mistakes. As earlyfilm noted, it's worthwhile to do the systematic tests and record the results in any case.

At this stage, I would focus on getting an image on the screen along with audio. Then you can do selective troubleshooting.

Good progress so far!

Phil Nelson

Howdy Phil!

Thank you for the words of encouragement! My one big, huge, overwhelming "if" was the CRT. I had no idea what it was going to do. Family legend said it was a "bad picture tube" that retired the set, but after I learned something about how vintage TV's work, the symptoms didn't fit. I had hope that something else was bad..now it's looking like it was a bad power switch all along. Still, the only positive test I could perform was your suggestion of checking the filament, and it did test good.

I'm not sure what to use for signal source.."earlyfilm" mentioned a slight voltage travels through the chassis on this set that could travel the lead and damage a transistor device...might it damage a VCR or DVD player?

Any suggestions?

If your VHS or DVD player has an output in the back marked "To TV" or "RF," you can connect that to the TV's antenna terminal through a coaxial cable.

If the player has A/V output (1 video plus 2 audio for stereo), then you can connect those to an RF modulator like this:

http://www.radioshack.com/product/in...95#tabsetBasic

You would then connect the RF modulator's output to the TV's antenna terminals, again using a coaxial cable.

This is how TV collectors watch recorded material on their TVs nowadays, since the USA discontinued analog TV broadcasts several years ago.

You can buy that kind of RF modulator other places; I only gave a Radio Shack link because their stores are found in many cities.

Earlyfilm was talking about a different connector on the TV -- the phonograph input jack. That was designed to use an old-school input. Modern solid-state devices (iPod, you name it) are not designed for that use and might be damaged if you plug them in directly.

It's possible your CRT is weak, but in the photo it is lighting up enough to see, so it should work well enough to get you through the restoration, at least. Perhaps when you're done it will be good enough to watch. The CRT used in these sets is not super-rare, so if you decide you need a better one, you should be able to find one eventually.

Phil Nelson

Cary,

First congratulations on getting one of the more complicated vintage TV sets, or I should say "systems," lighting up! These early Du Mont's are not what we call starter sets!

That set must have had years of dry storage storage! Usually one can hear the HV crackling up for the first time, but I forgot that you were from the driest area of the US.

Sorry I confused you. I was talking about modern AUDIO devices. Many of these are not protected against for this issue. Anything that is supposed to go through an antenna or video feed should be OK. Also, older tube era phonographs should be OK.

I'd try a your cable box if you have cable and it has an RF (channel three or four) analog output. If not, find one of the used set top boxes used to convert digital over-the-air programs in the early days of digital, that will be better. The most common problem with both of these is their output is slightly stronger than old high performance fringe area sets like your DuMont is expecting and that may cause sound buzz or picture bending, or even the picture flipping to negative.

The first thing to remember about a tube checker is that it also has to be recapped and then possibly recalibrated, since the same parts in them age just as a TV does.

Also you need to try to see if the focus control is just dirty or if it has failed. You have pretty high voltage there, so after cleaning, be sure to let the control completely dry before powering up the set, or you could fry it. This control is center fed from the raw B+ and helps provide both the 300v and 200v sources.

James

Not so, not with a Du Mont anyway. Sets that did no more than blank the raster with an external phono input are really nothing more than a gimmick.


Any design that was done at all seriously will cut the voltage to the sweep section when in a non-TV mode and the Du Mont sets do this.

ETA: Well damn. I just checked the RA-113 skiz and can see there came a time when the Du Mont engineers stopped being serious! Even my '51 Emerson combo kills the sweeps in phono mode...and it ain't no Du Mont.... :no:

Yeah, I was quite surprised to discover that while restoring an RA-113. I have a GE-802 with a beefy switch that cuts juice to most of the set while not in TV mode.

Cary,
Congrads on the successful power up. There is one paper cap i'd heartily recommend replacing as the first order of business. That's the coupling cap going to the control grid (G1) of the HO tube. The slightest leakage in this cap will cause the tube to overconduct, shortening its longevity.
If the tube is 6BG6, G1 is pin 5.



OOPs! Senior moment.:o Looks like you've already done a recapping. Presumably you got that one already.

Hi Cary,

I just 'tuned in' to this thread. Congratulations on resurrecting the Dumont. Not an easy first project.

I have a soft spot for DuMonts, obviously...:smoke:

http://i268.photobucket.com/albums/j...ps91b20d88.jpg

http://i268.photobucket.com/albums/j...psa85c7422.jpg

Turns out the rheostat that controls the focus is toast. About a third of the wire winds are eaten through.

I did hook up an old VCR/DVD combo with a built in RF output and was able to get a blurry picture..so that's good news.

Any hints on where I can find a 1200 OHM 25 watt ceramic rheostat with a long shaft? The Clarostat part number is RTV-220.

Photo soon...

Nice stuff! I hope to get as good a picture out of mine eventually. I just determined my focus control rheostat is a goner..

The SAMS calls for a 1200 ohm 25 watt rheostat...

Surplus Sales has a 1000 ohm 25 watt, left side of the page on link below..for $8..would that be close enough?

http://www.surplussales.com/Potentio...sRheost-4.html

Yup. Surplus Sales of Nebraska.

There's a 1k 25w and a 1.5k ?w on this page:

http://www.surplussales.com/Potentio...sRheost-4.html

Focus Controls are a soft spot on these old DuMonts.

Ooops. See you've already caught the SS of N page.

I bought a bunch of those a couple of years ago to keep in stock.

You can hang a 25ww resistor off the end of the 1k Control to gain a little more range, if need be.:smoke:

That's exactly what I installed in my RA-113.

http://antiqueradio.org/art/DuMontRA-113FocusPotNew.jpg

The shaft was too long, so I cut it down and filed a flat area to fit the knob.

Phil Nelson

Outstanding! Thanks for the input..I'll get a couple of those rheostats ordered so I have a spare around.

Restrung the tuner dial tonight. The list of "to-do's" gets shorter!

I called my mother a couple nights ago and told her "the DuMont lives!". She remembered when I hefted that sucker out of grandma's house and into her van, by myself, about 25 years ago. She used to watch that TV when she was a little girl. When she comes out to New Mexico for a visit later this year, it looks like she'll be able to watch it again. That's pretty cool.

Cary, if it were me, I'd also purchase one of the $1.25 10 watt 200 ohm resistors that Nebr Surplus has and add it on to one end of the pot. Yes, I know the new pot is within 20% of the original, but that pot and the focus coil are in a divider network in your power supply. I suspect that with both the new pot and that resistor in place your B+ supply voltages will be better behaved, and this could possibly improve your weak reception.

Jas

Thank you for the suggestion. I went ahead and ordered two rheostats and two resistors so I'd have a spare set. Does it matter which side of the pot I put the resistor on?

According to the tracking number, the package from Surplus Sales is on schedule to arrive tomorrow. I'm looking forward to install!

Whichever side puts the best focus nearest to the center of the pot.

With the non-open pot in the bleader circuit, it will shift some of the various "B" voltages and you may have to tweak some of the adjustments, including the ion trap.

J.