View Full Version : 1958 RCA Super Corner TV


fixmeplease
03-03-2016, 12:20 PM
RCA 21-T-8478 U (21T8478) Super Model. Photofact Set 386, folder 4, Jan 1958. Black and white TV

I picked up this Tv a couple months ago. The CRT tested ok except for the life test but I decided to give it a whirl as I really like how it blends into my corner with the angles of my paneling. Im surprised these corner tv's never caught on. As you can see the exterior is in pretty nice shape. Theres one knob a little broken up but I can live with that. No scratches on the glass front which means I never owned it, lol. The large back panel is in great shape but its missing the smaller one where the speaker is. There is a matching flip up lid on the top for controls.

Because of it being fairly difficult to work on and not wanting to damage the yoke taking it in and out (or resoldering it on countless times) I went ahead and replaced all the electro's, paper caps, bumblebees, and a fair amount of resistors, maybe 45-50 parts in all. I detached the yoke so it wouldnt get damaged as i had to flip the chassis over a hundred times. I could get at about half of the board parts from the back side and did those correctly, then did the crush method on the rest, which was a PITA. 5 tubes tested bad and I got replacements.

For some strange reason, it worked when I put it together! :) The CRT isnt real clear but its watchable and the sound is real nice. Good enough to watch news on, or other things like that. CRT is a 21DFP4 originally, but has an Emerald replacement. From my reading these were not very good CRT's.

I want to replace the seleniums which is one of my questions as I have never done it. It has 2, both .280A, RCA #104483. The replacement parts listed include Sarkes Tarzian #M500 which is silicon and are still available online at reasonable prices. Am I better off to use that part or to use a modern diode? And if modern, which number? Do I need to add another resistor? This is a hot set and in the pic of the rectifiers you can see the resistor above it is in poor looking shape. I'm still new to this stuff so it may be hard for me to understand real tech talk so I may have more questions.

My 2nd question involves the yoke. Can I add a plastic connector to the wires so that I dont have to remove it to remove the chassis? Or is that a bad idea? It solders to the chassis right now. The housing was in poor shape and I can still get it mounted and working with a part I made of styrene, but am sure I will damage it with repeated removal. The chassis removal isnt too bad except for the yoke.

Thanks in advance, and I will likely have more questions.

BigDavesTV
03-03-2016, 12:47 PM
Great looking corner set, "fixmeplease," and you're right, it looks very nice in that corner! Basically, it is a very good idea to replace the Selenium rectifiers. Do use new silicon diodes, do not use new old stock selenium rectifiers. You may or may not need a series resistance, sometimes the DC voltage output is close enough to the schematic value, to be ok. the Sams should list the voltage after rectified by the diodes, and that will be at proper line voltage, usually 117vac. The resistor above the seleniums, is a fusible resistor, and they often don't look great, even when they are OK. Yes, you can add a connector in line of the Yoke wires, I have done this more than once, for ease of service. I recommend using a mating M&F Molex or AMP Connector bodies, that have enough "pins" in them to allow you to add a little separation of one space, between the two or three heaviest Yoke wires, just my own opinion. Best wishes on your continued restoration of this classic, and uncommon set.

MRX37
03-03-2016, 01:41 PM
That's pretty neat looking. Yeah, odd they never caught on... Well actually they kinda did in a way. BPC sets slope like that in the back making them able to fit into corners.

Maybe those consoles never caught on because there was less room to set stuff on top of them.

dieseljeep
03-03-2016, 01:47 PM
I'm surprised, they used a series-string, hot chassis design, as the set was rather pricey at the time.
I think, they made one the next year that was transformer powered. :scratch2:

Electronic M
03-03-2016, 03:02 PM
That's pretty neat looking. Yeah, odd they never caught on... Well actually they kinda did in a way. BPC sets slope like that in the back making them able to fit into corners.

There were corner sets in the 50's (possibly the 60's though I don't have a specific example in mind) and Zenith had a modern corner console cabinet in the 70's and 80's. It's not that they only existed for a short time and disappeared, but more like they were around for a long time, had limited sales, and disappeared with the console market.

MRX37
03-03-2016, 03:08 PM
That makes more sense as not everybody would want a TV in the corner.

fixmeplease
03-03-2016, 04:02 PM
When I was searching for info on this set after I got it, 1957. 58, and 59 were the only years I saw mentioned. Your probably right EM about them being around longer. I think I found a Philco online too but dont quote me on that. I "think" there were 2 corner models that RCA made at this time and this is the cheaper one, called Malvern and around $300 new. The other model had solid square type legs. I will attest to the dowel legs strength as Ive had to spin it a couple times.

I was told that it came from the attic of a closed TV repair shop. There was this tv and a very plain Dumont tabletop in the sale. They were the only 2 tv's in the place he said, so I figured it probably wasnt junk. I did not win the Dumont. Theres a tag from 1964 inside when a new CRT was installed with the owners name on it.

What part number diode should I use to replace the seleniums? Im at a loss on that.

wa2ise
03-03-2016, 04:41 PM
Maybe those consoles never caught on because there was less room to set stuff on top of them.

Maybe the reason was that you couldn't locate the TV anywhere else than in a corner.

Kevin Kuehn
03-03-2016, 04:49 PM
What part number diode should I use to replace the seleniums? Im at a loss on that.

Nice job on the restoration. :thmbsp:

1N4000 series diodes should work fine. I keep 1N4007's on hand simply because they have the highest peak reverse voltage rating from that series.

http://www.onsemi.com/pub_link/Collateral/1N4001-D.PDF

fixmeplease
03-03-2016, 05:43 PM
WA2ise, good point! For giggles I just measured. If the back came to a point, the front of the TV is 24" from the corner. I would think that would give a few extra inches of floor space in front compared to the others. Against a straight wall it would look very odd.

Thanks everyone!

Phil Nelson
03-04-2016, 02:36 AM
Cool set. Those corner TVs are not often seen; I don't think I have ever seen a restored one.

The reason they never became popular is what everyone said. A corner TV will ONLY look good in a corner.

If you think that's a big limitation, try walking around your house and counting the vacant corners where you might sensibly put a corner-shaped piece of furniture. I did that a few years ago when we saw a corner cabinet that my wife really, really wanted. We live in a big house and there was absolutely NO place to put it -- not even close.

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

fixmeplease
03-08-2016, 10:02 PM
Just an update. I got the diodes in and the voltages seemed ok without a resistor. One check point is supposed to be 145V and measures 149V. the other is supposed to be 260 and is 256. Those with a DVM, for whatever thats worth. I did not measure it with the seleniums in, but I had to turn the brightness down a little now. That could be why or maybe the CRT came to life a little. I moved it back into the corner where hopefully it will be for a very long time. Thanks again everyone for the advice and comments.

Electronic M
03-09-2016, 01:01 AM
Those voltages (if they are the highest and next highest V B+ rails) are easily close enough to speck for it to be left as is. The brightness increase is likely from an improvement in B+....Those old seleniums can start to drop more voltage than they were designed to as they age/go bad.