Hi Gang,

Last Saturday I was able to pick the 24 in Muntz. I started tinkering with it on Monday. First order of business was to test the crt. The 24ap4 was still under vacuum. The crt is a rebuilt replacement. I put my B&K crt tester on it and all I could get was a crummy reading of 250 on a scale of 1000, where 200 is the cutoff between good and bad. After about an hour of warmup with no improvement I started to gently restore it. After working carefully I have achieved a solid 420 which I think will yield a watchable picture in a subdued lighting environment. With a brightener attached I get a solid 800. So if need be I can always go that route.

Next order of business was to fire up the chassis. I got sound but no picture and no high voltage either. So I shut it down and proceeded to carefully remove the chassis which has the 24 inch crt mounted on it. WHAT A MONSTER CRT. If you look at the rear view of the set with the chassis inside you can see that the crt occupys most of the cabinet interior. The crt is huge.

After I got the chassis out I carefully removed the crt from the chassis and put it aside.

Here is a tip I got from John Marinello on removing the crt. I have always had a bit of trouble with the crt socket hanging up on the focus or deflection yoke when sliding out the crt out. John said to tightly wrap a piece of paper around the end of the neck, covering the socket and the glass and tape it in place. That way when you slide the crt out, the lip of the socket can't get hung up on the inside of the focus and deflection yoke. thanks for the tip John, it works great.

So now I turned over the chassis. I was just appaled at the crapy repair work that had been performed on this chassis. All sorts of jury riged repairs including resistors that were just wraped around wires without even soldering. Several caps were completly drained of wax and you could see the foil bundle inside the cardboard tube. At some point the verticle output transformer and the deflection yoke had been replaced.

So Tuesday night I started recaping the old beast. I finished tonight. Then I installed my 5 inch test crt for the big test. The big question....will it work?...will there be high voltage?....will there be a raster?.....will there be video and audio?.....

YES!!!!!!! TO ALL OF THE ABOVE.

After a few adjustments and replacing a few weak tubes, I got a half way decent picture. I will leave further tweeking until after I have the 24 incrt installed and the chassis is put back into the cabinet.

A couple of oddities about this set....there is no HV cage, what you see in the photo below is what you get. You can't operate the chassis without the speaker because they have a power supply choke mounted on the speaker, and the audio output transformer is mounted on the chassis. Very wierd. In the photo of the set with the doors open, you will see what looks like a pencile box door that you would expect to find operator controls behind. But the door is not hinged, it clips on with some clips and comes completely off to access the controls. And the controls behind that panel dont have any knobs, just bare control shafts. Muntz was truely the king of cheap. The tuner dosent even have any fine tuning control. Talk about no frills, this set never heard of frills. The only controls on the front are on/off/volume, and contrarast, on the left, and the chanel selector on the right. No agc adjustment on the chassis either. I does however have horizontal linearity, (which some of my Zenith portholes do not have)

I will post additional pictures of this monster after it is completed. Until then these photos below will have to serve to wet your appetite.

Enjoy!

http://www.audiokarma.org/forums/attachment.php?attachmentid=61368&stc=1&d=1189662677

http://www.audiokarma.org/forums/attachment.php?attachmentid=61369&stc=1&d=1189662677

http://www.audiokarma.org/forums/attachment.php?attachmentid=61370&stc=1&d=1189662677

http://www.audiokarma.org/forums/attachment.php?attachmentid=61371&stc=1&d=1189662677

http://www.audiokarma.org/forums/attachment.php?attachmentid=61372&stc=1&d=1189662677

http://www.audiokarma.org/forums/attachment.php?attachmentid=61373&stc=1&d=1189662677

Good grief, that chassis is bare bones!
The little 8" RCA's have more parts than that!
Kinda surprising the Madman used a transformer instead of a voltage doubler power supply.

That set really lives up to the madman's cost cutting reputation.

Well, I can see why I thought it was their equally rare 19" set. It's the same chassis! And, that was also a bear!
Yep. Nice, and cheap. Nice, and cheap. Great job bringing this monster back to life. How does the picture look with it's original CRT?

Did you also put new electrolytics in? You were truly lucky to find this set. I wanted it, but, just couldn't go pick it up. At least it's been saved. Great job...
Bill Cahill

Thanks Bill,

I have not installed the 24 inch crt yet. When I do I will post photos of the finished project.

I have not restuffed the cans yet. I will be doing that shortly, when the new electrolytics arrive. I also wanted to see if the other major components were functional before expending the effort. No sense in puting a lot of work into a chassis if some unobtanium component is defective.

I wouldn't worry too much about the crt. Even ones I've seen that are at the '?' work good enough. It seems to be when that needle only moved 1/4" or so that you really have a problem.

One thing about a Muntz chassis like that...there really isn't much that can go wrong!

Kinda surprising the Madman used a transformer instead of a voltage doubler power supply.

You can bet he got a good deal on the trannies from somewhere! ;)

Wow! I thought my electrostatic Motorola 9VT1 was a simple chassis. I see there are very few setup controls also. I would expect this set to have imperfect linearity, retrace lines, yoke ringing and other performace anomalies associated with inexpensive sets. The only bragging feature is that it has a 24" screen. Any idea what that set sold for new? Please post a picture of it set up with the original CRT. I'd love to see what one of these looks like when operating according to factory specs.

If Muntz was alive today he would probably make an LCD set where the entire chassis consists of one surface mount IC embedded into the back of the display.

I think there are more caps in a Motorola VT-71 than in the Muntz. I counted around 27 looking at the underside photo. Can't wait to see a shot of the 24" crt.
kevin

Hey Bob:

That set is looking good! I suspect that it will produce a pretty nice picture. That chassis is not all that bad. It still has three stages of IF which is more than some sets had. The really stipped down Muntz's came out a few years later. I think that big chassis helps to make it look so bare. I'm currently working on an unusual Motorola VK-101 and I'd much rather work on the Muntz!

Steve

Bob,

Great work on the Muntz! How much HV does the set produce? Looking forward to pictures of it operating.

Hi John,

According to my Pamona HV probe which has a 0 to 40KV scale, I am getting 16KV at the socket on my 5" test crt.

It will be at least 2 more weeks before I have the set completed. I have ordered caps to restuff the cans and will be going on vacation for a week before the caps get here. After the cans are restuffed, I will re-install the 24inch crt and post another photo of the BIG tube operating.

Bob

Hi Kevin,

Actually there were 23 caps if I countd the dead ones correctly. Stay tuned...photo of the big tube will be about 2 weeks from now.

bob

Hi Steve,

So when are we going to see a photo of that VK-101 Steve? Saw a photo of one in the net. Cool looking set. You sure have good luck in getting some cool sets.

I think the Muntz will probably get a pretty fair picture from what I see on my test crt. also need to do a little touch up work on the cabinet. It has a few scratches and is rather dirty. The chassis had a lot of soot on it from being in a dirty basement for many years. Need to take the safety glass off and clean that area real good too. Need to patch some tears on the speaker cone too. But most of the hard work is already done except for re-stuffing the cans.

Bob

Aw shucks guys, you make me want to restore my 1954 RCA Victor Model 21-T-373 instead of getting rid of it...

Nice job on the Muntz TV.

Sal Brisindi

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.

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.

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.

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

Dave A

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

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

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

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 :)

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.

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

Very nice work on the Muntz!

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 :tears:

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.

That is way cool, Bob.

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.

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.

Experiment with the horizontal osc. screen grid resistor. You may be able to reduce the width without losing HV.

You know, reading up on Earl Muntz, I think he had the right idea, at least with TV's.

I don't know about reducing the amount of IF gain to simplify the circuit, but simplifying the rest of it doesn't seem like a bad idea at all.

The simpler something can be made, the less there is that can go wrong, and really, a black and white TV shouldn't have to be that complex.

Problem was that he eliminated things that were needed unless you lived close to the transmitter. Sync was touchy, and gain was marginal, so that AGC couldn't handle fading very well. Also, as you've discovered, no width adjustment.

Very cool though it's hard to get a sense of the size from a picture.

Is that Julia Child on the screen or Dan Aykroyd?

If I were to build a TV, I'd go with as simple of a design for the chassis that could provide good performance. I wouldn't do this to save on costs, but to make repairs and servicing easy. I would use a CRT that would last for at LEAST 20 years, probably a studio monitor grade CRT.

So, I guess I'd go cheap on the chassis, but all out on the CRT. To me, the CRT matters the most.

Very cool though it's hard to get a sense of the size from a picture.

Is that Julia Child on the screen or Dan Aykroyd?

It was a cooking show on the local PBS station, Don't know who she is.

I will try and post another photo later this week with a 12lp4 next to it for size comparison. That should give you a good idea how huge this crt is. although it is still 6 inches smaller than the tube in the Dumont Royal Soverign. I guess that one qualifies as gigantic.
Bob

I swear the picture of the working set on the right looks like COLOR!!!

Hi,

In electronics engineering, the art of designing a device with minimal components as cheaply as possible is called "Muntzing". This set is a pure example of Madman Muntz engineering. Worked OK 10 feet from the TV station! Not so hot when the TV station was a DX catch!

Well, the cabinet refinishe project took longer than I expected. 2 weeks total. Cabinet had a number of major gouges and scratches, so the repair work was more involved than originally thought. Front doors were of particular difficulty, as they took about a dozen coats of lacquer to level all the scratches. One coat per day with wet sanding every other coat.

I hope to one day get a good crt for this set. This one is not very good. I have to drive the video so hard that it causes poor picture detail.

Below are several photos.

First one is the chassis sitting next to an RCA 12" to get an idea of the size of the crt.

Then the complete set sitting next to an RCA 21" console for relative size comparison.

The last 3 are just to show.

All in all an interesting set, but picture quality is inferior to most of the sets I have worked on. I think a better crt would improve that issue a great deal though.

Enjoy!

Wow Bob, that really looks great!

I tell ya those two crt's look a heck of a lot different in size than 9". Anybody else get what I'm saying?

Great job on the Muntz! They may be cheap but this is on nice looking set. Much more stylish than many better made sets I have seen, like G-E's to name one.

Tubejunkie, I don't follow you.

The difference in size between the Muntz 24 and the RCA 12, sitting on the bench is 12 inches.

The difference in size between the RCA 21 inch console and the Muntz is 3 inches.

Where are you comming up with 9 inches. Or did you think the Muntz was a 21 incher. The Muntz is a 24 inch roundie.

Sorry, my mistake. I think what I did is got to thinking about the picture and scrolled back and saw 12" and right under it 21". Somehow I went on and applied those #'s to my thoughts on the picture. Brain Fart bigtime!!

Its funny after I posted that I got to thinking that the two complete sets in the other picture look a lot more than 3" different in size. At least I got the math right. I think....

Nice work! Wow, there's a lot of unused acreage underneath that chassis! Bet that drove Muntz nuts wondering how he could save a few pennies by cutting back on the sheet metal.

Reece

I hope to one day get a good crt for this set. This one is not very good. I have to drive the video so hard that it causes poor picture detail.



And Yoda knows a brand new 24AP4 is on its way...

I had the opportunity to visit Bob yesterday and see his collection including this 24 inch Muntz. He did a beautiful job on the restoration, both cabinet and electronics. It looks even better in person than the pictures here show.

Steve

I am curious about your small test CRT. Do you have multiple ones of various characteristics to accommodate many different chassis requirements? Or did you just get incredibly lucky on this matchup? And how safe is it to run 16.5 KV on a 5 inch CRT? Isn't that way more than it needs?
Regardless of all that, congratulations and a big salute to you! --Tom in Tucson

That little test crt is a special crt desgned to be a universal replacement. The high voltages do not seem to bother it, and it does not need an ion trap. It is one of the handiest items I have. Bought it on epay for about $5 plus shipping. They come on epay every once in a while, and are usually pretty inexpensive.

Tom,

The 5" test CRTs (such as the 5AXP4, and later 8" versions) were specifically designed to work in almost any electromagnetically deflected TV. The 5AXP4 features a max working anode voltage of 18KV, and automatic self focusing. While the picture displayed on the screen might be overscanned in higher deflection angle TVs, the image was (is) still useable for making checks.

Nice job on that very pretty Muntz. The picture you show is probably about as good as it'll get. Does that set indeed have 3 picture IF stages? Most Muntzes I've encountered only had 2. Sensitivity and bandwidth converge at very poor compromise.

Also sync circuitry was minimal. And forget about keyed AGC.....

Not sure what to tell you on the horizontal oversweep issue. If you do take steps to try to reduce the amplitude keep a sharp eye on your HOT cathode current, lest it exceed tolerable specs.