All I can see is the CRT neck at this stage. Nothing else printed on the glass of the neck. On the base it says Made in U.S.A. 5-22.

I just noticed that someone wrote in pencil on the bottoms of two guns. One says 5/13, the other has an asterisk drawn on it.

Phil Nelson

http://antiqueradio.org/art/RCATM-10CRTBase.jpg

If that date code is correct, there are older 21AXP22's out there. The one in my 21-CT-55 has 4-52.

Some 15G's have production id numbers etched inside, but I've never seen pencil before. No contamination issues apparently.

Yes, it's a 'new' 15G. Not many around with 1955 date codes. As was speculated before, this may be either selected or, considering the inside dates, custom built for a TM-10.

Pete

So, the date code is something like year-week (5-22 being 1955, 22nd week)?

It didn't occur to me that the penciled numbers would also be a date code.

If I get some time later, I can look inside for etched codes.

Phil Nelson

P.S. New is good for me, from a customer standpoint. The last thing I want to buy is the first example (of anything) off the assembly line :)

That would be my guess too...

And the gun was either assembled "rodded" or wired 9 weeks earlier (5-13).
jr

Don't really matter when it was made, its STILL Kewl as all H3ll, one of the best scores I've heard of since the "Prototype" set... This is almost as good as findin' a 1903 Ford Model "A"....Yes, they DID make Model "As" B4 1927...Henry couldn't bring himself to follow up Model T w/a Model "U" or "V", so he started over...

MORE DATE CODE Stuff...
 

That is so -- for RCA in the fifties. What ticks me off is when, in the next decade, RCA went to letter date codes for their 7- and 9-pin tubes.

As some of you know, I am slowly working on a 1956 Philco model 22D5102 color set with the TV-233 chassis. In the set, a Philco-branded, SYLVANIA-built 6AW8A date code -- for the 30th week of 1958 -- is "58 30", with the 58 stamped above the 30. However, a PHILCO-built 6M3 damper in the same set is stamped "249". I speculate based upon the history of the TV-123 in question that it stands for the 49th week of 1962.

Pete

Working at my usual snail's pace, I have gotten as far as easing the monitor onto its (protected!) face, so's to remove the CRT and get a peek at the nether bits. Looks pretty clean and unmolested underneath. I like that orderly layout.

After counting electrolytics (46) in the parts list, I decided to make a spreadsheet for ordering parts and keeping track of things that I replace.

Phil Nelson

http://antiqueradio.org/art/RCATM-10...erOriginal.jpg

http://antiqueradio.org/art/RCATM-10ChassisFaceDown.jpg

Rca tm-21
 

I have an RCA TM-21 that was purchased from NBC in New York about 30 years ago. It was FULLY restored to PERFECT working order by Herman Reynolds III and Bill Cushman in 1987. The only problem with it is that the anti-glare glass that attaches to the picture tube has started to separate.

I have an RCA TM-21 that was purchased from NBC in New York about 30 years ago. It was FULLY restored to PERFECT working order by Herman Reynolds III and Bill Cushman in 1987. The only problem with it is that the anti-glare glass that attaches to the picture tube has started to separate.

What an awesome project! I am sure you will have fun with this one, Phil.

Does it have RGB inputs? If so, it should provide a superior picture if sourced from Y, Cb, Cr.

Wouldn't that be fun? I don't see any inputs like that, though. On the first page of this thread is a photo of the back panel, showing jacks labeled R, G, and B, but they are identified as test points in the manual. Likewise, there are test points for I and Q.

I told myself I couldn't start on this guy until I cleaned up some of the long-delayed and half-finished projects I've had sitting around for as long as 13 years. Only one more to go, and then I can get busy on this.

I have assembled a complete set of good tubes for it and I have a sackful of new caps ready to install.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Dan-

Welcome to Videokarma.

That sounds like a nice monitor. The picture tube (CRT) problem is commonly called a "cataract", and it can be fixed by a couple of different methods. One big discussion here on VK can be found by searching for the word "cateract" (notice the mis-spelling).

If you want to discuss your monitor more here on Videokarma, it would be best to start a new topic, and copy your notes above into that new topic.

How old is this monitor?
Gush, it "swallowed" "only" 450 Watts!!!

The consumer version (CT-100) was 475 watts...

I'm counting on that CT-100 to help me reduce my heating bill in the wintertime, once I get mine operational. It will be a decent source of electrical heat. :)

I guess the remaining 25 watts was the tuner, IF strip and audio?

The CT-100 and this monitor use the same 15GP22 CRT, which was quickly superseded by bigger tubes, so I assume they were contemporaneous -- 1954 or soon after. A monitor could have remained in service for years, of course.

You might think they could simply strip the tuner, IF, and audio from a CT-100 and say, "Hey, I've got a monitor," but it's a little more complicated than that. This monitor uses 31 tubes vs. 37 in the CT-100. After I restore it, I'll write an article including block diagrams & schematic so people can compare.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

The monitor probably uses different tubes, since some of the features of the CT-100 would not be needed. Does it have sound at all, or is this thing strictly video?

It's a video monitor.

http://antiqueradio.org/art/RCATM-10...ockDiagram.jpg

Phil

Update? Phil must be busy!:yes:

Working even more slowly than my usual snail's pace, I have begun replacing electrolytics & whatnot in the TM-10 monitor. In the service manual, someone penciled in a little modification to the power supply:

http://antiqueradio.org/art/RCA_TM-10_P-S_Mod.jpg

The mod would add two 7-ohm, 25-watt resistors in series with the selenium rectifiers, presumably to reduce surge on startup.

I'm debating whether to substitute something like CL-60 thermistors for the resistors. If you have an opinion on that, vote early and vote often.

I have begun an article about the restoration. Obviously, there will be much more to come.

http://antiqueradio.org/RCA_TM-10_15GP22_Monitor.htm

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Any chance you can copy the mounts and ball bearings of those wand magnets? Not sure, but I seem to recall that the prototype needs a couple of those.

Making exact copies would take metalworking equipment that I don't own. Here are some photos that give an idea how they work.

http://antiqueradio.org/art/RCA_TM-10_Convergence01.jpg
http://antiqueradio.org/art/RCA_TM-10_Convergence02.jpg
http://antiqueradio.org/art/RCA_TM-10_Convergence04.jpg
http://antiqueradio.org/art/RCA_TM-10_Convergence03.jpg
http://antiqueradio.org/art/RCA_TM-10_Convergence05.jpg

The wands have a spherical part that allows movement within the mount, which is a simple clamp with beveled holes. At the ends, little swiveling clamps hold the cylindrical magnets.

If somebody held a gun to my head, I might try to fab something out of brass stock (assuming it wouldn't matter if the wands were non-ferrous). The spherical part could be a brass bead with a hole drilled through the center, soldered in place. The magnet clips on the end could be as simple as a piece of wire soldered to the wand and wrapped around the magnet. The magnets are practically weightless.

Eventually, I'll need to figure out how to replace the two missing magnets. Perhaps I'll try cutting bits from a frig magnet.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Nice job on the start of your restoration article Phill! Looking forward to seeing more as time goes by. It's giving me a good idea of what I have to look forward to when I get to a point when I can start the restoration of the TM-10 I acquired a while back.

Thanks. Balloting is still open on whether to use a thermistor in place of a resistor in that little modification. Since I already have some CL-60s on hand, I'm leaning in that direction. Or, perhaps it doesn't really matter.

I'd normally just put something in and then monitor voltages when I bring the set up for the first time. The rectifiers are not in a convenient place, however. To remove the cage around them, you need to pull the CRT and yoke, which does not invite casual experimentation.

Phil Nelson

Phil-

Since you are likely to replace the selenium rectifiers with silicon diodes, wouldn't you kill two birds with one stone if you put in dropping resistors along with the diodes?

Your new restoration page for this monitor looks great.

Yes, good point. A dropping resistor should do.

Meanwhile, I'm trying to decipher what was done to this set. The choke L34 is missing. Nothing left but a rubber stamp on the chassis and two empty mounting holes.

The parts list describes it as "reactor: choke coil," giving a stock number of 78961 and no other specs.

The choke is connected between the junction of rectifier CR1 and capacitor C3 and its other lead goes to terminal 1 of R241, the screen purity control.

Perhaps someone intended to replace the choke, which had failed and caused other problems. The wires have been ripped from R241 and from R3, the purity control. Both of the 22-ohm resistors wired in parallel with those controls have broken in half. In this photo of R3, you can see that someone crimped a salvaged resistor around a couple of ripped-out wires, maybe as a reminder to "fix this someday."

http://antiqueradio.org/art/RCATM-10_R3_AsFound.jpg

I'll sort out the wiring eventually. Not so sure where to go for a replacement choke. I don't have bins of spare parts on hand, and the manual gives no spec for it, other than the stock number (78961).

Phil Nelson

Phil:

That same RCA part number is used in the CT-100 as a filter choke. L57 in Sams. .63ADC, 17.3 ohms, .6HY. The only sub Sams lists is Triad C-40X. Thordarson Catalog lists 26C81 as their sub.

I would love to have a unit like this. I remember the 21" round version of this set from RCA and Conrac and wanting one of them, too, knowing how well-built they were.

I look forward to seeing this set pass an image soon. I'm very glad that you saved it.

Thanks, I should have thought to look that up.

I contacted Moyer and they said that they have the Thordarson part. Yay!

Phil Nelson

FWIW, the Triad C-40X is still in production, and available from Newark:

http://www.newark.com/triad-magnetic...0-20/dp/03F765

Well, I'll be darned. It's available from Mouser and Allied, too, and all at about half the Moyer price.

Phil Nelson

So what fried the choke ?
 

:tears:Something made it get real HOT:tears::tears::tears:

Yah, and which was the chicken and which the egg?

Did those 22-ohm resistors fail and take out the choke? Or vice versa? Or, did a failure in some other part fry them all? So many unanswered questions in a chassis that's still 98% unrestored :)

Phil Nelson