The Family DuMont

[Phil Nelson]

Originally Posted by CaryLee

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

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



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

Phil Nelson

[CaryLee]

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.

[earlyfilm]

Originally Posted by CaryLee

I'll get a couple of those rheostats ordered so I have a spare around.

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

[CaryLee]

Originally Posted by earlyfilm

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!

[earlyfilm]

Originally Posted by CaryLee

Does it matter which side of the pot I put the resistor on?

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.

[CaryLee]

Originally Posted by earlyfilm

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.

Well, I had a 50/50 chance of getting the extra 200 ohm resistor on the "right" side of the focus pot...and I got it wrong. Best focus is now with adjustment turned all the way to the left. Pulled chassis to move 200 ohm resistor to other side of pot.

I did get a MUCH better picture, though. Eye Tube still very dim. Think it's a bad tube, since I could see faint action looking directly at tube.

As far as the picture goes, a lot of "ghosting", and the top of the screen bends right..I think...I've been looking at the screen in a mirror as I make adjustments out back.

Gonna move resistor and try again. Don't think it's going to change picture quality much, if at all. l

[M3-SRT8]

As far as the Dumont tuning tube is concerned, you will notice that there is a resistor installed at the back of the socket. These are frequently bad, and need replacing.

[CaryLee]

Originally Posted by M3-SRT8

As far as the Dumont tuning tube is concerned, you will notice that there is a resistor installed at the back of the socket. These are frequently bad, and need replacing.

Thanks!

[CaryLee]

Got the new focus control yesterday, and like Phil said earlier, the shaft is a tad longer, and needs the flat filed into it. A little work with the Dremel tool and it was ready to go.

These controls from Surplus Sales of Nebraska were packaged in 1960! Talk about NOS! I almost hated to open up something that was sealed in it's package when Dwight Eisenhower was President.

[CaryLee]

In the interim I had also cut new glass for the dial window to replace the broken one.

I've read references to both plastic and glass being used for the dial window. It looks like mine had some extra "fingers" soldered on to hold thicker glass than what was originally in it. Don't know the history of that modification, but apparently it was for standard 1/8 inch window glass, because that is what fit.

Does anyone know if the brass trim around the dial window is solid brass? It's not magnetic, so I think it is. There's a bit of pitting on the bottom near the tuner knob..probably from fingers touching it. I'm wondering how much polishing it can take. I don't want to polish brass plating off if that's all there is.

[holmesuser01]

The resistor on the tuning eye is inside the base cover. On my set, the tube was bright, but had only minute movement on the display. The new resistor brought that back.

The tube is a 6AL7-GT. It's not terribly expensive.

[kvflyer]

Originally Posted by holmesuser01

The resistor on the tuning eye is inside the base cover. On my set, the tube was bright, but had only minute movement on the display. The new resistor brought that back.

The tube is a 6AL7-GT. It's not terribly expensive.

And the value of the resistor is often 1 meg ohm. Check it for color bands and since you are going to the trouble of checking it, might as well replace it with a new one?

[CaryLee]

Originally Posted by holmesuser01

The resistor on the tuning eye is inside the base cover. On my set, the tube was bright, but had only minute movement on the display. The new resistor brought that back.

The tube is a 6AL7-GT. It's not terribly expensive.

I've got another 6AL7-GT in the mail on the way to me..due Friday. You are absolutely correct about them being pretty cheap..shipping and all it was around $8. Much better than the eye tube for my 1938 RCA 99K! The 6U5 tube that radio uses are going for astronomical prices on Ebay..last one I bid on ended up going for over $30, but not to me.

Not sure what the deal is with my eye tube, but figure I can't really dig into it until I have one I know is good, or I could end up chasing a "problem" that doesn't exist. When I first turn the set on and it's warming up, the eye tube will light a little bit, not real bright but visible, then it fades out. It's never a real "crisp" looking display even when I can see it, and the tube display has a smeared "burned" look to it even when there's no power to it.

[CaryLee]

Spent this morning watching "Cahill, U.S. Marshall" on the DuMont, while working on adjustments to the set. I've got a big mirror sitting in front of it so I can see what affect the adjustments are having.

I want to thank everyone who has offered advice to this novice! I've been able to resurrect my grandparents old Teleset from a novelty/conversation piece/plant stand to an actual, working television!

It does seem the picture tube, while viewable, is not near "bright". I'm getting a full picture, have been able to center it in the CRT, and can get it pretty well focused. Unless there is some other factor that affects brightness, I'd say I am going to have to go on the hunt for another 19AP4. Not an easy task out here in New Mexico, where there are VERY few vintage televisions. I am VERY happy with what I have, though, considering the set has been "dead" for around half a century.

There are some very thin diagonal white lines that appear on the CRT from time to time, mostly they seem to be associated with the brightness and contrast settings. They cross the CRT from lower left to upper right. So skinny, I've not been able to photograph them. They do not distort anything on the screen. Any hints?

I've noticed that the "Brightness" control affects the focus quite a bit. Is this normal?

Lastly, when tuning, with the continuous tuner, I've noticed the picture seems to come in well, then seems to lose it's sync (get "wobbly"), then comes in good again before tuning out. I've attempted to sync the sound to the places where there is the best picture, but the sound seems to want to come in strongest closest to the "wobbly" picture. Any hints on what to check for?

Thanks!

[kramden66]

your brightness focus issue and lines which are retrace lines and lack of brightness suggest a weak crt , if you are not planning on running it for hours on end and only an hour or so a day or every other day I would put a brightener on it , you will get better brightness , contrast and less of the lines and control the focus / brightness , if you had a crt tester you could see what it reads , my Dumont has a weak one so I put a brightener on it but added a resistor so its only 7 or so volts , this is enough to improve the picture and not push it that hard , at 7 volts emissions rise to good on mine, a regular brightener could be 8 or 9 volts , If you don't have one I might be able to space one.

as far as the wiggle it could be where you are at in tuning range , if you reduce the agc it may improve this as well and reduce the wobbly effect .

mike