View Full Version : Nearly finished with this RCA 21D7487


Eric H
01-04-2014, 12:04 AM
This set is from 1957.

I took the chassis out for a preliminary examination, to remove it you also have to unbolt the tuner from the side of the cabinet and remove that along with the chassis, a cumbersome situation to say the least.

Knowing the RCA often put a mounting location on their color sets for the convergence board to sit while servicing the chassis I started looking for something similar on this, it only took a minute since the length of the wires limited the options.

Two screw holes on the side of the chassis with a slight convex bump to them, spaced exactly right to line up with the holes on the tuner bracket!

There were no screws present so perhaps they were removed or never supplied by RCA but they are threaded the same as the chassis screws so a couple screws and washers and I was in business.

Sams doesn't mention this but I'd bet it's in the RCA factory service literature?

This set also has the worst case of yoke rot I've seen, the cover on the back of the yoke holding the centering ring (only one) is completely crumbled to dust, even the yoke itself is distorted somewhat. I have a couple Triad replacement yokes but they don't come with the cover, they too are starting to distort some but are much better than the original so I'm going to swap one of them in.

bandersen
01-04-2014, 12:46 AM
Nice looking set. According to the Riders index, it's known as "The Ramstead" and covered in volume 19-89.

Username1
01-04-2014, 12:59 AM
2 AM and 7 of us can't sleep......

Nice set.... I'm goin back to bed.....

good luck.........

You have that back together by morning....

Eric H
01-04-2014, 01:55 AM
2 AM and 7 of us can't sleep......



You have that back together by morning....


No problem :D

Actually I brought it up on the Variac with a test CRT and got a raster!
When i tried it a few months ago I just got an electrolytic getting hot, must have reformed the filter somewhat, it still get's warm at 90 volts but at least it runs.

Tubejunke
01-04-2014, 08:48 AM
No problem :D

Actually I brought it up on the Variac with a test CRT and got a raster!
When i tried it a few months ago I just got an electrolytic getting hot, must have reformed the filter somewhat, it still get's warm at 90 volts but at least it runs.


IF it gets warm, replace it quickly..

Edit: Sorry Eric, I didn't even look at who was posting. I know that you know this. I was thinking it may have been someone newer to electronics.

Kevin Kuehn
01-04-2014, 11:49 AM
I like it!

Your chassis looks very similar to my 21-D-7177. It's somewhat challenging to replace the caps on the PC boards. I ended up sneaking in through the back holes in the chassis with the soldering iron. I also had the crumbling yoke cover and had to make a wooden replacement for mine.

wa2ise
01-04-2014, 12:18 PM
IF it gets warm, replace it quickly..
.

The fact that the TV sorta works indicates to me that it's worthwhile to do a full recap, as the important unobtanium parts are functional (flyback, power transformer, CRT, yoke).

kvflyer
01-05-2014, 03:36 AM
The fact that the TV sorta works indicates to me that it's worthwhile to do a full recap, as the important unobtanium parts are functional (flyback, power transformer, CRT, yoke).

"Truer words were never spoken". That is always a plus.

walterbeers
01-05-2014, 06:49 AM
Nice set, but don't even try to reform the capacitors especially the one that that gets hot. I brought a TV up once that an electrolytic popped and blew out a bunch on smoke. Great set to restore though, as the raster means at least the flyback, yoke,and power transformer is good. Hope the CRT has good emission. Good luck with your project!

hi_volt
01-05-2014, 08:23 AM
Very nice looking set and great 50's styling. Definitely worth restoring. Love the swivel base.

DavGoodlin
01-05-2014, 10:08 PM
Nice set. It will be helpful to see how you un-solder the capacitors. Otherwise RCA's are such a treat to work on. :)
I have a 1956 and a 1959 with the same obstacle. Those channel windows were so cool and it seems only RCA had them.
What is that funky white cheesy-smelling stuff on the knobs? I get that sometimes and the only cure is to toss em in the dishwasher.

In the era of mahogany or limed oak, is that finish a dark blonde with highlights?

Eric H
01-06-2014, 12:07 AM
In the era of mahogany or limed oak, is that finish a dark blonde with highlights?

The dark areas seem to be Walnut Veneer, the front is a Yellow/Blond, probably some type of painted finish but it seems to be real wood underneath.

Cabinet is good, it just needs to be wiped down with a little stain to fill in some small scratches here and there, the yellow is in great shape.

The knobs are okay, they just need polished up, the flash made them look whitish, the cogged belt driving the channel number dial is broken, I'll probably just fix it in place on channel three since it doesn't really have to function any more.

It didn't have a back when I got it but someone over at the Antique Radio Forum sent me one.

dieseljeep
01-06-2014, 10:39 AM
Nice set. It will be helpful to see how you un-solder the capacitors. Otherwise RCA's are such a treat to work on. :)
I have a 1956 and a 1959 with the same obstacle. Those channel windows were so cool and it seems only RCA had them.
What is that funky white cheesy-smelling stuff on the knobs? I get that sometimes and the only cure is to toss em in the dishwasher.

In the era of mahogany or limed oak, is that finish a dark blonde with highlights?
I used to unsolder the entire board when replacing caps on the vertical board. there was just too many of them, that needed replacement.
The .01/600V cap in the horizontal wave form circuit, I used to unsolder, though the access holes. I even replaced it in the home. I carried orange drop caps in the caddy, for that.
I pulled the chassis and set it on top of the tube caddy, so I didn't have to disturb the tuner and that lousy belt, as the leads were long enough.
On the '57 model, the tuner unplugged and you could remove the volume, contrast control, without removing the TMA. :yes:

Tubejunke
01-06-2014, 11:30 PM
I have found that a sets age and how long it has gone in dormancy dictate the need for full recap jobs. To be specific, my oldest set is a 1947 model, an RCA. I have a 1950 RCA as well and both sets required complete recaps; no way around it. However, many later 50s and almost all 60s sets will do fine with the original electrolytics. Just get rid of everything else non polarized except ceramic discs.

Funny how as much as this topic comes up and we talk about "full" recaps, I venture to say that most of us don't go through the ceramic discs, so really it's not a full restoration. Not saying it is wrong, because they have proven to be ultra reliable and it would be a waste of time and money to swap them out for what these days may just end up being an inferior part. Like the old TVs and radios, they just don't make them with the quality that they used to in many cases.

Electronic M
01-06-2014, 11:41 PM
Orange drops also often are still good, but there are exceptions to that.

Eric H
01-18-2014, 07:06 PM
I have replaced all the Electrolytics, recapped the Horizontal board and most of the Vertical board and now have a nice stable picture.

There are some white ceramic tubular caps on the vertical board I haven't changed yet, they are 10% tolerance Elemenco's.
I suspect the yellow caps we use are probably also within that tolerance but I think I will order some better caps from Mouser for that circuit since vertical is always troublesome with thermal drift and linearity issues.
The image is so good I may skip recapping the video circuits for now, it has sound also and I don't want to screw up the alignment.

This is running an 8" test CRT.

Eric H
01-21-2014, 09:00 PM
This set has been a really easy restoration, probably because it was refubished in 1964 and probably run well into the 70's.
It started with a raster, new electrolytics and papers in the Horizontal board got me a good image, most of the rest didn't affect it much and there are still three old caps in it that I don't have on hand.

Picture is really bright and sharp, picture really doesn't do it any justice.
Sound is loud and clear and I didn't have to fiddle with the i.f. cans at all to get it that way. this is the Deluxe chassis which probably helps the performance too.

I had to fabricate a new yoke cover centering ring retainer because the old one rotted to dust.
The centering ring does nothing so I shouldn't have spent so much time on it. :no: The centering is fine anyway.

Einar72
01-21-2014, 10:38 PM
The centering is excellent. Nice job, Eric!

Electronic M
01-22-2014, 12:42 AM
The centering magnets should have an effect...Assuming they did not get degaussed over the years.

Kevin Kuehn
01-22-2014, 01:00 AM
I'd have to take mine apart to verify, but I think Eric's may have something missing from it's centering ring assembly. It sure seems like it needs to be able to modify that large permanent magnet behind it.
How can a piece of aluminum alone do that? :scratch2:

Eric H
02-02-2014, 08:03 PM
I'm pretty much done with the electronics on this set, it works really well!

It's been playing Gilligans Island for the last few hours while I worked on other stuff so I made a short video to show it off.

http://www.youtube.com/watch?v=XC-KLSxT02I