My new project. Dumont Television

[mkoser]

Well I decided to take a gamble... I ran the set for about three hours tonight while I was sorting through the sams and cleaning my workshop. I was watching the history channel, and it was as if I was watching the current news!

In the three hours that it ran, the picture didn't fade, flicker, distort or change in anyway.

There is also absolutely NO hum at all in the audio....

The question is.... should I recap it, or just let it alone?

I'll take pics of the chassis this week.

MK

[Eric H]

If those caps have a blue and orange Sprague label they've probably been changed.

If the originals were black they are probably hot and covered with a paper tube to keep you from getting shocked, watch out, if the replacements aren't covered they may live!

If they are mounted directly to the metal chassis then no problem but if they are mounted in a Phenolic insulator chances are they have B+ on them.

[Jeffhs]

I agree with old1625 -- the picture on your DuMont set looks almost perfect. I'd keep that set if I were you. Like Zeniths, they don't make DuMont TVs like yours anymore (the DuMont Corporation has been out of business for decades, although I do remember seeing the DuMont name being used [under license] on some 19" portables as late as the 1970s).


I never saw a DuMont round-tube TV with the separate FM tuning dial until now. In fact, the only other DuMont TV I ever saw in my life was, IIRC, an RA-112 console, 35-some years ago. That set had the famous DuMont Inputuner which tuned continuously from 54 to 216 MHz, with FM smack-dab in the middle of the dial. (The tuning eye was in the same spot on the tuning scale, and the FM band was clearly marked with the letters "FM" directly above it.) As this set only had one tuning dial and knob for both high- and low-band VHF TV and FM, I don't think the dial drive was that complicated--no more so than the dial cord in the better radios of the period.

Now I'm wondering. Since these DuMont sets had FM and also a very good audio system (your console looks like it has at least one good-sized speaker in the base of the cabinet), did they also have a phonograph input? As good as these TVs must have sounded for standard television shows and FM radio, I think it would have been a terrible mistake if the company had not included provisions for a phono turntable as well. These TVs have the potential to be all-in-one entertainment centers (albeit oldish, of course) if they do have the phono input.

[mattdavala]

Isn't there a turntable in the pull out drawer? My Dumont had its turntable stolen out of it. What brand turntable is it?

Best regards,
Matt Davala

[batterymaker]

If it were a Bradford, it should be an RCA 45 player, probably an RP-168 motorboard. But I've now noticed that this isn't a Bradford, so disregard my post. I'm a memory, forget me.....:-)

[bgadow]

The next time you run it for an hour or more, shut it off and then feel those filter caps. If they are really warm to the touch, change them. If they are about the same temp as the surrounding chassis I wouldn't worry about them. I would echo Eric's warning about B+ being on those cans.

My experience is that electrolytics from the 60s are still good most of the time, but their time is running out.

[mkoser]

Here are some pics of the cans and overall chassis.

Yes it does have a record player... It works like a charm!

http://flickr.com/photos/8293453@N08/3214510470/ one of the cans

http://flickr.com/photos/[email protected]/photostream/ the chassis, notice the labels on the cans

http://flickr.com/photos/[email protected]/photostream/ original caps?

http://flickr.com/photos/[email protected]/photostream/ picture kinda blurry, it's the camera.... not the tube

http://flickr.com/photos/[email protected]/photostream/ record player

http://flickr.com/photos/[email protected]/photostream/ the AM has its own dial scale... not the FM


do you guys think these caps are original???
thanks for looking,

MK

[Eric H]

The can in the first picture has definitely been changed, note it's mounted on an insulator.

I'd bet it's hot in relation to the chassis, just how hot I don't know but it wouldn't hurt to check it with a meter, you'd hate to lay your arm across 450 volts!

[Old1625]

That Sprague can must be a replacement. The can behind it may also be; you could try to pull the cardboard sleeve and see. The cans may be isolated merely so that they can be "star grounded" at another point, but more likely they are hot.

That the record player "works like a charm" tells me that this set has had some fairly recent and extensive TLC.

You're talking about a near 60-year-old set, and electrolytic capacitors can die on the store shelves in half the time, and the original idler drive puck in the changer would be glazed over like a golf ball, or altogether just dust and crumbs in the turntable pan. Also a crystal cartridge in the tone arm that is still giving output is likely to be a replacement in my experience; the crystal element in the original would have its bushings in dust, and would likely itself not be in good shape. Six decades is a long time.

The advice from bgadow about checking can temperature is good--along with the warning about voltage levels.

[mkoser]

If I recall, there are 5 cans with the Sprague label on them. There is one can with the cardboard over the can, but I didn't look closely at that one yet.

If they were replaced, it must have been at least a little while ago, since the dust on the chassis is consistent everywhere.

I see what you are saying about the phono...

Im just wondering, if this guy I bought the set from did some major work to it:
A)Why wouldn't he tell me (selling point!)
B) Why would he still only charge me 100 bucks...

I'm certain that the "picture tube warranty" card I found inside with a date on 1970 is authentic. It was wedged behind the chassis, with a thick layer of dust on it.

[Old1625]

Originally Posted by mkoser

If I recall, there are 5 cans with the Sprague label on them. There is one can with the cardboard over the can, but I didn't look closely at that one yet.

If they were replaced, it must have been at least a little while ago, since the dust on the chassis is consistent everywhere.

I see what you are saying about the phono...

Im just wondering, if this guy I bought the set from did some major work to it:
A)Why wouldn't he tell me (selling point!)
B) Why would he still only charge me 100 bucks...

I'm certain that the "picture tube warranty" card I found inside with a date on 1970 is authentic. It was wedged behind the chassis, with a thick layer of dust on it.

That's a head-scratcher to be sure....

At least the set must've been maintained up to when that CRT got put in. And unless it was a resto project such as we do, it is possible that the set was still in general use at least up to that time.

I guess it can happen; I was given an old Westinghouse table set that had an RCA Silverama replacement CRT put in it at some point. Unfortunately the back was missing, and the chassis was covered in deep mud. I literally hosed the mud out with water, reinserted the tubes after applying tuner cleaner and lubricant to the sockets and controls. After the set dried I simply plugged it in, and the darn thing worked perfectly. It ran for 2 years of regular use before the seleniums let go, and stank us out of the house.

In your case I think you got real lucky.

If you can see any of the blocking and bypass caps that would originally be bumblebees or wax-dippers you might want to replace 'em for grins--or do as I would do; just watch the TV and enjoy!

[nasadowsk]

That power transformer looks like it can power a few TV sets. It's freaking huge!

[Old1625]

Originally Posted by nasadowsk

That power transformer looks like it can power a few TV sets. It's freaking huge!

I'd made many a hefty power amp in the early days from power transformers cadged from '50s era TVs; they could be had for nothing usually, and $free was what I generally could afford. Most of those amps were powerful enough to get the attention of the police on occasion. Except for color sets on occasion there was nothing much in TV transformers after about '59 or so that attracted my attention for other use, as sets became much more energy efficient.

If you have any Sams dating back to the early '50s study what the power requirements were for these picture-producing space heaters....

[mkoser]

I talked to the guy I got the set from last night. He told me that he may have replaced the caps in 1970. I think he probably did when he did the tube replacement.

He said he can't believe that he forgot to put the chassis bolts back in...39 years ago....

This explains the caps issue.

Now my issue is, how well do new (1970 vintage) caps hold up.... Should I replace them again, or leave them be???

They do not get "hot" when running, only about the same temp as the massive transformer and tubes.
Matt K

[zenithfan1]

It sounds like they are good. Is there any way you can test the ESR on them?