24 inch Muntz restoration has begun

[ohohyodafarted]

I finally got around to re-stuffing the cans last night. And today In installed the 24 inch monster crt. Fired it up and it works (sort of). Picture is less than desireable because the crt is weak. (I am working on a lead for getting another crt)

But the more difficult thisn is that I have problems with Horiz and Vert stability. The controls are very touchy and nearly impossible to lock the picture. When you can get a lock it dosent hold, and the slightest touch of the H & V controls will start the picture rolling.


Bad part is to work under the chassis, I am going to have to remove the 24 inch crt because there is no way to work on the chassis with the crt installed. The thing is just too big. I will sub my 5" test crt for bench work.

Is there a common area that would effect both H & V locking ability. Picture is just too unstable to be of any use. Tested and swaped a lot of tubes but that has not helped.

I figured one of the experts here might be able to steer me in the right direction.

[peverett]

I would check the sync seperator circuit if both Vertical and Horizontal will not stay locked.

Another possiblity is the AGC circuitry, but ususally the picture is overloaded also when this is defective.

[Eric H]

I was going to suggest checking the resistors but it doesn't look like that set has any!

But seriously, I would look for resistors that have drifted up in value, especially ones that were high value to begin with.

[Dave A]

Or does this thing need a massive amount of RF to be stable?

Dave A

[Eric H]

Dave makes a good point, what are you running it off of, antenna or DVD?

[ohohyodafarted]

Originally Posted by Dave A

Or does this thing need a massive amount of RF to be stable?

Dave A

You may have something there Dave. When this chassis was on my bench here at home using a 5 inch test crt the darn thing seemed to be very stable. In conjuction with the above, you should understand that I live in the middle of where all the Milwaukee transmiter towers are located. I am less than 1 mile from no less than 6 1000 foot high transmiter towers with several stations per tower. The signal here at my home has always been way overloaded. It bleeds into everything.

Today when I installed the 24 inch crt, it was at my workshop at the factory where I work. That location is about 3 miles further away from the towers, and the signal is noticably weaker at my workshop.

Perhaps I should try and feed a DVD player into the set and see if it is stable that way?

But even if it is a mater of weak signal, I would have to think the set needed to perform better than this when it was delivered. Otherwise nobody would have been able to watch the thing under normal signal conditions.

Going to try some more tubes tomorrow before removing the big crt.

Thanks for all the suggestions,
Bob

[ohohyodafarted]

Originally Posted by Eric H

Dave makes a good point, what are you running it off of, antenna or DVD?

At home I was using a 3 foot long peice of 300 ohm twinlead. at the factory today where the instability manifiested itself, I was using a set of rabbit ears.

I am going to take a DVD player to the factory tomorrow and try that first. But even if the DVd player works, that means that I am going to have to figure out why it dosent lock on a normal signal that other sets have no problem with. There must be something out of wack.

Will update my findings here tomorrow night.

Bob

[Eric H]

Could be something wrong, or it could just be a Muntz with so little gain it just wont work well unless you live next door to a transmitter

[peverett]

Reminds me of a story about a Muntz TV. A former TV repairman told me that he had a customer in Dallas who owned a Muntz. It worked fine in Dallas, near the transmitters. When the Dentist retired, he moved about 100 miles from the transmitters, taking the Muntz with him. Of course, it would not then work, so he asked the repairman to fix it. As it was so cheaply made, it was hopeless.

[ohohyodafarted]

Originally Posted by Eric H

I was going to suggest checking the resistors but it doesn't look like that set has any!

But seriously, I would look for resistors that have drifted up in value, especially ones that were high value to begin with.

BINGO! you were right on the money Eric. a 3.9 meg resistor on the 12at7 sync/sep tube. It had gone to 8.2 meg. I also replaced a couple of other resistors that were about 30% out of tollerance too. Picture seems nice and stable here at home. Tomorrow I will reinstall the 24 inch crt and hopefully if all goes well I will take a couple of photos and post them here tomorrow.

Don't know what that 3.9 meg resistor does but it seems to have fixed the problem.

I also pulled the drum out of the tuner and cleaned up all the contacts, and the picture improved quite a bit.



Thanks for pointing me in the right direction.


Bob

[wajobu]

Very nice work on the Muntz!

[ohohyodafarted]

I installed the crt this morining and did some tweeking on the tuner and now we have a working set. Picture is not that great. A better crt would help so I dont have to drive the video so hard to get a picture, but it's not too bad, if you stand far enough away. Detail is not so great, but then this set has a minimum amount of tubes and the circuits have very few components.

I started the process of re-finishing the cabinet today. That will take most of next week. When the cabinet is ready I will reassemble the complete set and take some final photos to post here. I need to have a new safety glass made, because the putz that I am, I broke the original getting it out of the cabinet

I think the knobs on the doors are not original. The current set of 4 knobs has an antique copper finish and the rest of the metal parts on this set are antique brass. Also there are marks on the wood behind the knobs that suggest that there may have been some metal rosettes against the door behind the knobs. I dont have a photo of the set when new so I don't know what kind of knobs are suposed to be on the doors. In any event I will get a new set of antique brass knobs so they match the rest of the hardware.

So here are 2 photos of the chassis with the big 24 inch tube operating. My machine shop is in the background.

[John Folsom]

That is way cool, Bob.

[wa2ise]

Originally Posted by ohohyodafarted

In conjuction with the above, you should understand that I live in the middle of where all the Milwaukee transmiter towers are located. I am less than 1 mile from no less than 6 1000 foot high transmiter towers with several stations per tower. The signal here at my home has always been way overloaded. It bleeds into everything.


Bob

That's about the only place a Muntz TV would get decent reception.. :-)
"Mad Man Muntz" designed his TV sets to be super cheap. bare minimum of an IF strip, for one thing. He'd often go into his development lab and randomly snip out resistors and caps to see if the set could do without.

Later on, the FCC mandated minimum performance standards for TV sets.

You can back off on the height a little. As the cabinet masks off some of the top and bottom of that roundie tube.

[ohohyodafarted]

Originally Posted by wa2ise

You can back off on the height a little. As the cabinet masks off some of the top and bottom of that roundie tube.

I will do that, but unfortunately there is no provision to reduce the horizontal width, and when you reduce the height, round objects in the center of the screen become oblong left to right. Got any suggestions to reduce the width. it is at least 4 inches wider than the actual crt. If I move the lateral control on the neck of the tube, I can't even find the left edge, although I can find the right edge of the picture.