View Full Version : Majestic 70 Leatherette restoration


cluelessgame
08-28-2016, 11:59 PM
A while back I rescued a 17" Majestic model 70 set from the gruesome fate of being turned into an aquarium. The chassis is a little rusty, the damper tube went to air, and there was a (thankfully empty) bee's nest hanging below the HV cage, but the picture tube tests pretty good and for $100 it was mine.

It appeared to have been to the shop early in its life - a few replacement caps here and there all those early plastic type - but no major red flags...yet

Being a set that I may sell at some point, I decided to shotgun the set and do a full recap. currently, I have replaced all of the paper/wax caps, both original and the early replacements, but have yet to do the electrolytics. I slowly powered it up and am getting a wide, bright line 1/4-way down from the top of the screen that flickers like the vertical is trying to start but can't.

The brightness control makes this line go from bright to completely dark, contrast control has no effect. focus control has negligible effect, so do all the vertical controls. horizontal controls change the pitch of the HV whine and there is no sound whatsoever. I've yet to check/replace resistors, but I know there are some that are bad (some have turned completely white from heat). and the B+ is a little low.

My main issue at the moment is that there appears to be things present (and looking original from the factory) that are not in the SAMS. It also appears that a bit of modification has occurred around the on-off/volume/contrast control stack. I already know the on-off switch doesn't work and had to jump the terminals for the power up. one end of the volume pot is, instead of tied to ground as the SAMS shows, jumped to the wiper pin of the contrast pot. from there, there is a piece of old component lead that goes to nowhere (hanging).

As for the other two pins of the contrast pot, one is attached to a green wire that goes up and is spliced with electrical tape to a smaller brown wire to a terminal strip lug and from there another green wire snakes up to another terminal strip lug where a 100 ohm resistor (not in SAMS but looks original) bridges over to pin 8 of the video amp tube. The other pin has another green wire that goes to a terminal strip lug, and from there, a tan(probably white) wire goes up to pin 5 on the video detector tube, while a resistor (another one that looks original but not in the SAMS) bridges over to a TS lug that two power resistors coming off the focus control are tied to. Both wires connected to the contrast control are obviously not original as they are hacked and melted all to hell.

Does anyone have a copy/scan of the Rider or factory service info in this set? or any info on the company "Majectic" in general? It seems like they weren't around for very long. This set does appear to be equipped for some sort of color conversion device, probably CBS's color wheel prototype. There's a switch on the back next to a 3-pin plug.

Electronic M
08-29-2016, 07:32 AM
I used to have a console with that chassis. Go after the whitened resistors first....When they turn white they are shot, and the set will not work properly with them that way.

Sam's is prone to errors, and often did not record production changes. If wiring looks stock get all parts in the circuit tested and on spec first, then if that fails note now it was wired when it came to you (so you can go back if needed) then make it match the schematic...Don't mess with the video/contrast till you have vertical sweep.

The tuners in these can get monstrously dirty, clean it well once you try to get signal through it. IIIRC I lifted a channel strip out and used it to hold a rag soaked in contact cleaner to the drum and rotated the drum till that rag got the hidden fixed contacts clean.

dieseljeep
08-29-2016, 10:59 AM
A while back I rescued a 17" Majestic model 70 set from the gruesome fate of being turned into an aquarium. The chassis is a little rusty, the damper tube went to air, and there was a (thankfully empty) bee's nest hanging below the HV cage, but the picture tube tests pretty good and for $100 it was mine.

It appeared to have been to the shop early in its life - a few replacement caps here and there all those early plastic type - but no major red flags...yet

Being a set that I may sell at some point, I decided to shotgun the set and do a full recap. currently, I have replaced all of the paper/wax caps, both original and the early replacements, but have yet to do the electrolytics. I slowly powered it up and am getting a wide, bright line 1/4-way down from the top of the screen that flickers like the vertical is trying to start but can't.

The brightness control makes this line go from bright to completely dark, contrast control has no effect. focus control has negligible effect, so do all the vertical controls. horizontal controls change the pitch of the HV whine and there is no sound whatsoever. I've yet to check/replace resistors, but I know there are some that are bad (some have turned completely white from heat). and the B+ is a little low.

My main issue at the moment is that there appears to be things present (and looking original from the factory) that are not in the SAMS. It also appears that a bit of modification has occurred around the on-off/volume/contrast control stack. I already know the on-off switch doesn't work and had to jump the terminals for the power up. one end of the volume pot is, instead of tied to ground as the SAMS shows, jumped to the wiper pin of the contrast pot. from there, there is a piece of old component lead that goes to nowhere (hanging).

As for the other two pins of the contrast pot, one is attached to a green wire that goes up and is spliced with electrical tape to a smaller brown wire to a terminal strip lug and from there another green wire snakes up to another terminal strip lug where a 100 ohm resistor (not in SAMS but looks original) bridges over to pin 8 of the video amp tube. The other pin has another green wire that goes to a terminal strip lug, and from there, a tan(probably white) wire goes up to pin 5 on the video detector tube, while a resistor (another one that looks original but not in the SAMS) bridges over to a TS lug that two power resistors coming off the focus control are tied to. Both wires connected to the contrast control are obviously not original as they are hacked and melted all to hell.

Does anyone have a copy/scan of the Rider or factory service info in this set? or any info on the company "Majectic" in general? It seems like they weren't around for very long. This set does appear to be equipped for some sort of color conversion device, probably CBS's color wheel prototype. There's a switch on the back next to a 3-pin plug.
Majestic seemed to have a relationship with Wilcox-Gay and Garod.
Their address was in Chicago, but they were possibly built elsewhere, maybe Michigan!
They also made phonograph records, that didn't sound or wear very well, like Sonora. :no:
Their products, weren't the best or the worst and disappearred around 1955 or so.
BTW, I like your idea on building shelf supports using plumbing fittings and pipe.

dieseljeep
08-29-2016, 12:02 PM
Service information is in Riders TV #8, the only Majestic in that manual.
The Volume control connections are low end to ground, wiper to .005 cap to grid of 6T8 triode, high end through a .047 to TV-phono switch.
The contrast control high end goes to pin 8 on the 12AU7 video amp and the wiper goes to ground through a 100 ohm resistor.
The Sams should be close enough in this area. They seldom goofed up that bad! :scratch2:

cluelessgame
09-08-2016, 02:55 AM
thanks, dieseljeep!

unfortunately now I think I've really hit an issue...possibly the reason the set was retired in the first place. it appears that the secondary winding of the vertical blocking oscillator transformer has gone open :sigh:

SAMS only lists a Majestic part number: C-9.230-4 with PRI:160ohm and SEC:1.3Kohm. I doubt I'll be able to find an exact replacement, but there are tons of them in stock on oldradioparts.com...I guess I just need to figure out (roughly) what the ratio is.... does anyone have a ballpark-estimate of a substitute range? It's for a 6C4 with 155V at the plate, and -48V at the grid if that helps.

cluelessgame
09-09-2016, 01:07 AM
Here's a picture of the transformer itself

Kevin Kuehn
09-09-2016, 11:37 AM
Majestic number C-9.230-4 crosses to a Thordarson 26A03 which has a 1:4.14 turns ratio. Thordarson lists others with that same ratio, but the mounting scheme and dimensions vary. There's a 26A03 listed on the ETF website, also one on ebay. http://www.earlytelevision.org/flybacks.html

cluelessgame
10-12-2016, 01:30 AM
Thanks Kevin! Ended up getting the one off of eBay, hooked it up making sure to get the orientation correct (comparing the SAMs to the diagram provided in the box) and....still no vertical....no raster, that is. There was some deflection though - the solid horizontal line was now flickering wildly in an area about 2 inches wide. The vertical size control had some, yet minuscule effect.

traced every bit of the vertical section over and over, only discovering a lack of voltage on the plate of the 6C4, but no indication as to why. All of the other components were correctly wired, and values were in tolerance. I even substituted a different 6C4 with no change. I began to suspect the b+, but all voltages were reasonable. One interesting phenomena, though, was that if I flip the switch on the back into color mode, the screen goes dark (as it should), and then flip it back, there's about one full vertical sweep, and then back to the 2" wide line of garbage.

Eventually, I decided to try swapping the leads of the secondary coil connections, and that did the trick!
When originally installing it, I noticed that the secondary output wires appeared to be color coded backwards to what the SAMs had. According to the diagram packaged w/ the replacement, the yellow secondary lead came out on the same end as the blue lead on the primary side (as opposed to in the SAMs where the blue and green leads come out the same end. so I wired it yellow to grid, and green to the 1.5M/4700MMF junction. So sure of myself that this was correct I didn't even consider it to be the issue until after weeks of pulling my hair out tracing the B+

So yay, I got that part fixed! Now on to the current issues:

Although I finally have full deflection, itís not a stable raster. It still flickers erratically, regardless of where the vert. hold is set (does have some effect). After grounding the wipers of the volume and contrast controls (which had apparently come undone) I managed to feed in a signal. The picture produced is able to lock in, so the flickering is from something outside the sweep circuit (I think).

At the moment, I suspect the flickering is somehow caused from the arcing Iím hearing (but canít locate) in the HV cageÖprobably should have mentioned it earlier, but since I was getting SOMETHING on the screen, I figured Iíd address it after the vertical gets fixed. Iíve cleaned off everything Ė having to remove the picture tube, focus and yoke mounts in order to take the cage off to get to everything Ė and discovered that this was a type of set that has a doorknob capacitor with the 1B3 socket screwed on top. Do those typically go bad? Its 500MMF rated for 20000V. There are also two resistors under the socket that are in tolerance, and everything is coated in some sort of black insulating gunk (corona dope?). Its chipped off a little in places, but the arcing doesnít appear to be coming from thereÖIíve pretty much narrowed the sound down to the tube itselfÖwhen I push on it the sound changes. I crimped up the contacts in the socket for a tighter fit on the tube pins, but that didnít help, so now I think itís coming from inside the base of the tube. Iím waiting on a new one to arrive to verify. Does anyone know if that can cause vertical flickering?

On an unrelated note, it also appears that one side of the audio output transformer is open. SAMs identifies it as Majestic Part No. C-9225-3C / Merit RO-16 / Chicago RO-16, having impedance PRI: 7.8KΩ / SEC: 4.1Ω ||DC res PRI: 450Ω / SEC: 0.7Ω. At the moment I am unable to track any of these down. How crucial are these listed values? I understand other types of transformers are selected based on resonance, but are audio output transformers as sensitive?

Electronic M
10-12-2016, 02:46 PM
My audio trans was bad too. I just grabbed a single ended 50C5 based one out of a Decca HiFi/stereo phono only console I scrapped for the changer...It worked fine. Any single ended audio transformer from a tube device should work decently.

Look for arcing/ corona in a totally dark room.

Sam's is full of errors on MANY of it's prints....I've found so many that I NEVER assume any info in sam's is correct. If sam's says 'the sky is blue' I'm going to look out the window and check before I assume they are right. If you do work based on the sam's verify it against the set and part in any and all ways possible.

cluelessgame
11-03-2016, 01:06 AM
Found the source of the arcing sound...turns out the HV "doorknob" capacitor went bad. By chance I noticed it was really hot when poking around and so I pointed my IR thermometer at it and powered it up and the temp jumped up into the 150's almost immediately after the sizzling began. I unscrewed the 1B3 base from it and powered the set on (holding the tube up with a wooden stick) and sure enough, the sound was gone and I had 10000+ volts at the suction cup! Unfortunately, it seems that the only replacement I can find is one going for $40 on amazon X.X

still no progress with tracking down a new audio output trans. (though, I haven't really looked) but I have found a few kinda close (but not really) on oldradioparts.

with the picture tube removed, I decided to do a little cleaning on the chassis. I tried doing what Bob Andersen has done in a couple of his videos - paint on some Rustoleum rust stripper, wait a few minutes, then wipe it off with a wet cloth, and then spray on some DeoxIt. I first tried it on the area that would normally be hidden inside the HV cage and it turned out pretty well. Then I did it over the big empty area under where the picture tube sits and now that whole area has developed a uniform layer of rust :sigh: did I forget something? I'd like to get the whole chassis all nice and pristine (again, I may be selling this one down the road) but I'm afraid to go any further. I also tried it on a small area on the side and, while no rust has formed (just slightly) the area seems to have gotten darker and sort of splotchy.

Kevin Kuehn
11-03-2016, 12:07 PM
Lots of folks seem to desire an even shinny chassis, but that uneven dull finish that develops over time on a chassis is actually a protective oxide that's formed on the surface of the cadmium or whatever plating was applied over the bare steel, in fact it was meant to do that very early in it's service life. It's actually the plating's less invasive oxidation that protects the underlying steel from rusting. Of course using anything corrosive to clean a plated surface will also remove part or all of that remaining finish. Once the plating is gone, then the remaining bare steel absolutely will flash rust unless it's thoroughly flushed of contaminants, force dried, and immediately treated with a new protective coating. So if it's a perfect looking finish you desire, you're better off cleaning with a degreaser, and then painting the plated metal surface.

bandersen
11-03-2016, 02:59 PM
I agree with the previoius post. I'm sorry you had bad results. That rust stripper trick works best on thick cadmium plating. I suspect yours is bare steel, has a very thin cad plating or is plated with something else. Also I don't think I used DeOxit, more likely WD40. DeOxit is expensive stuff. The idea is to leave a protective film. More recently I've been using Boeshield. It's a metal corrosion inhibitor developed by Boeing that works very well.

Electronic M
11-03-2016, 04:06 PM
Cadmium is also rather toxic so removing it is not the best for your health. Unless I have a rare chrome plated chassis or a factory painted chassis in front of me getting it shiny is of no interest to me....Hell I'll often leave mild brown-orange rust alone (if it ain't obvious from the outside) or hit it with a clear rust converting primer and leave it. Unless you've had rust-THROUGH happen it should have no bearing on the electrical function (though it can indicate a need to clean contacts).

cluelessgame
11-18-2016, 01:37 AM
I'm happy to report that the new doorknob cap did the trick. After replacing an out-of-spec resistor in series with the vertical hold I finally achieved a stable picture! :yippy:

right away, other issues became apparent. As far as picture quality is concerned, it's pretty...meh...watchable by far, but it's out of focus in appearance (the drawn image, that is. the electron beam itself is pretty crisp) and any text around the size of a nickle or smaller is hard/impossible to read - there's a bit of ghosting/smudging as well. Contrast is not that great, even when its maxed out and brightness is adequate, but very washed out and blooms a bit when turned all the way up.

I guess I should pause here and clarify that yes, I've tested the picture tube. emissions are well into the good. life test is iffy - the needle does fall into the "?" range if you hold the button long enough. I know its never going to be as nice and bright as a NOS aluminized tube, but I'm still pretty convinced its not achieving its full potential (too bad I can't just give it a motivational speech)

there are several parts of this set that appear to be modified, and other parts look original but aren't that way in the SAMs, most of which I mentioned earlier in this thread, but at the time I didn't pay much attention to it as I was too busy trying to get the vertical oscillator to work.

to reiterate: it appears that someone connected the free end of the contrast pot to the 210V bus through a 220K resistor. also connected to that side of the resistor is a long wire that runs up and over to pin 5 of the 6AL5 video det - agc rect tube. the SAMs shows it connected to pin 7 of the 3rd video IF amp 6AU6, which, from there has a 5000pF cap and 150ohm resistor paralleled to ground. The schematic calls for pin 5 of the 6AL5 to be around -.2v... it currently measures anywhere from +2v up to almost +5v with the contrast turned all the way down. The end of the wire connected to the contrast pot appears hacked in, but the other end, as well as the long wire to the 6AL5 and the 220k resistor all look original. turning the contrast knob also affects the sync as well. I tried hooking the long wire to the 6AU6 like the SAMs calls for, but noticeable change was observed.

The brightness control is wired differently as well. the SAMs calls for one end to be connected to the 210v bus. instead, its connected to the higher 260v bus (yet again, appearing to be original). according to Grob, brightness control works via cathode biasing, and the lower the cathode voltage, the brighter the picture...would switching it to the 210v bus brighten it up?

other issues: the picture also appears very stretched horizontally, but unfortunately both the horizontal width and linearity controls have no effect whatsoever. both are coils with screw/ferrite slugs mounted inside the HV cage, and both ohm out to the correct resistance.

lastly, there's an accross-the-board voltage anomaly...all of the voltages, including the one directly off the plates of the 5U4, are a good 30% higher than what they should be...and that's on 117v line voltage...even the HV cup is up into the 14-15KV range when the SAMs only calls for 10.35KV...perhaps with the primary side of the audio output transformer being open (I've have yet to track down a replacement) could it not be drawing enough current to bring the voltage down? or have I discovered free energy?

Kevin Kuehn
11-19-2016, 01:32 AM
The 6K6 audio output would normally pull about 30ma, which certainly will have some influence on power supply regulation, but I have my doubts if it would account for your overall 30% voltage increase. In all honesty it's not a bad looking picture you have there, contrast looks acceptable for that ambient room lighting. Does the focus control have any influence on the picture sharpness? Your scan lines do look to be fairly well focused. If the beam bender(ion trap) is mis-adjusted that could be limiting the max brightness.

dieseljeep
11-19-2016, 11:30 AM
I'm happy to report that the new doorknob cap did the trick. After replacing an out-of-spec resistor in series with the vertical hold I finally achieved a stable picture! :yippy:

right away, other issues became apparent. As far as picture quality is concerned, it's pretty...meh...watchable by far, but it's out of focus in appearance (the drawn image, that is. the electron beam itself is pretty crisp) and any text around the size of a nickle or smaller is hard/impossible to read - there's a bit of ghosting/smudging as well. Contrast is not that great, even when its maxed out and brightness is adequate, but very washed out and blooms a bit when turned all the way up.

I guess I should pause here and clarify that yes, I've tested the picture tube. emissions are well into the good. life test is iffy - the needle does fall into the "?" range if you hold the button long enough. I know its never going to be as nice and bright as a NOS aluminized tube, but I'm still pretty convinced its not achieving its full potential (too bad I can't just give it a motivational speech)

there are several parts of this set that appear to be modified, and other parts look original but aren't that way in the SAMs, most of which I mentioned earlier in this thread, but at the time I didn't pay much attention to it as I was too busy trying to get the vertical oscillator to work.

to reiterate: it appears that someone connected the free end of the contrast pot to the 210V bus through a 220K resistor. also connected to that side of the resistor is a long wire that runs up and over to pin 5 of the 6AL5 video det - agc rect tube. the SAMs shows it connected to pin 7 of the 3rd video IF amp 6AU6, which, from there has a 5000pF cap and 150ohm resistor paralleled to ground. The schematic calls for pin 5 of the 6AL5 to be around -.2v... it currently measures anywhere from +2v up to almost +5v with the contrast turned all the way down. The end of the wire connected to the contrast pot appears hacked in, but the other end, as well as the long wire to the 6AL5 and the 220k resistor all look original. turning the contrast knob also affects the sync as well. I tried hooking the long wire to the 6AU6 like the SAMs calls for, but noticeable change was observed.

The brightness control is wired differently as well. the SAMs calls for one end to be connected to the 210v bus. instead, its connected to the higher 260v bus (yet again, appearing to be original). according to Grob, brightness control works via cathode biasing, and the lower the cathode voltage, the brighter the picture...would switching it to the 210v bus brighten it up?

other issues: the picture also appears very stretched horizontally, but unfortunately both the horizontal width and linearity controls have no effect whatsoever. both are coils with screw/ferrite slugs mounted inside the HV cage, and both ohm out to the correct resistance.

lastly, there's an accross-the-board voltage anomaly...all of the voltages, including the one directly off the plates of the 5U4, are a good 30% higher than what they should be...and that's on 117v line voltage...even the HV cup is up into the 14-15KV range when the SAMs only calls for 10.35KV...perhaps with the primary side of the audio output transformer being open (I've have yet to track down a replacement) could it not be drawing enough current to bring the voltage down? or have I discovered free energy?
I hope you didn't have to pay $40 bucks for the doorknob cap. :sigh:
You should start hitting the Hamfests and swapmeets for some of those parts or listing it on this sites "wanted" column. The cap and the output transformer as well. :scratch2:

old_coot88
11-19-2016, 11:35 AM
Just a SWAG regarding the smearing of fine detail in the pic.. since there's evidence of hacking in the video amp area, maybe someone has tried to hack in a DC restorer circuit. Maybe you could post the schematic of the vid amp area.

Need to determine first if the smearing is occuring 'downstream' of the video detector or :eek:upstream of it. Always think of the vid detector as the "continental divide" when localizing any kind of smearing/ringing problem in the displayed image.

Kevin Kuehn
11-19-2016, 11:59 AM
From Riders. How about all those video peaking coils?

http://i452.photobucket.com/albums/qq245/Kuehn/VK%20Pictures/Majestic%2070%20Video%20Circuit%20Close%20Up_zps9c 8af2dv.jpg

http://i452.photobucket.com/albums/qq245/Kuehn/VK%20Pictures/Majestic%2070%20Video%20Circuit_zpsnv8vol7k.jpg

old_coot88
11-19-2016, 12:28 PM
Re. the hor. overscan and excessive HV, you could reduce the screen grid (G2) voltage on the H.output tube. But that would exascerbate the blooming problem.:sadwave: Maybe a piccy of the Hor sweep area..

Kevin Kuehn
11-19-2016, 02:32 PM
What do you all think of that two stage video amp circuit? The video detector is dc coupled to the 1st video amp grid. Then there's a dc path from it's plate through R33 all the way to the CRT grid. The only coupling cap is C30 between the 1st and 2nd video stages. I'm thinking there's no need for additional dc restoration. :scratch2:

old_coot88
11-19-2016, 06:08 PM
One other thought.. What is the heater voltage? Is it running substantially above 6.3 VAC?