This should be fun (RCA TM-10 15GP22 monitor)

[Phil Nelson]

It's a video monitor.

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

Phil

[miniman82]

Update? Phil must be busy!

[Phil Nelson]

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

[miniman82]

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.

[Phil Nelson]

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

[ohohyodafarted]

Originally Posted by Phil Nelson

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

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.

[Phil Nelson]

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

[ChrisW6ATV]

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.

[Phil Nelson]

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."



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

[Tim]

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.

[holmesuser01]

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.

[Phil Nelson]

Originally Posted by Tim

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.

Thanks, I should have thought to look that up.

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

Phil Nelson

[N2IXK]

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

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

[Phil Nelson]

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

Phil Nelson

[WA3WLJ]

Something made it get real HOT