RCA 630TS Power Supply

[Jonathan]

I am in debted to all you guys on the forums for helping me these past two years. I purchased a lot of old TVs and radios from ebay, getting to ambitious thinking I'll be able to bring them back to life. Well, of the 10 or so TVs I purchased, none of them work, as I have been trained on modern electronics, these old sets get the better of me. Once again, thanks for all your help and effort in responding to me. You guys are the only ones who can really help and you've done a great job.

Now for a slight change in subject. The RCA 630TS power supply, how exactly does it work? It looks to me that all of the set's current goes through the H and V pots. Is this normal? Can they handle that current or am I reading wrong? I measured across both pots and their resistances are about 20 ohms. This doesn't seem normal. The 250uF 50V cap failed and released all it's smoke the last power on, which I think voltage across it was exceeded quite a bit. I'm stumped and almost ready to pack it up and have it shipped to one of you guys for repair. I'm tired of it sitting on my bench for a year.

Thanks guys.

Jonathan

[mattdavala]

I feel safe knowing someone else will reply with more knowledge. I have no real electronics knowledge. I want a chance to take a stab at the power supply here and learn some from other people that will reply.

The B+ current does go though the controls, and they are of low resistance. They have to be because there is hardly a voltage drop before and after the pots. 280 Volts off the cathode of the rect tubes and 275 at the highest B+ output.

If the capacitor blew, disconnect the positive lead from the cap and power up the set using a variac, or light bulb in series trick to prevent something else from smoking.

Check your B+ voltage and compare to what the schematic says. You didn't mention it, but did you replace the electrolytic caps yet? Thats the most likely reason it failed. Others will fail too in a matter of time.

Good luck fixing this set. I'm 25 and have the luck of repairing one TV and it was due to re-capping the TV. It was a 56' model GE and not too complicated. Your 630TS would be a complete nightmare for me! I would be dreaming of paper caps chasing me. . . . chasing me towards . . . . towards . . . dreaded Black beauty caps!!! AHhhhh.

Good luck! Oh if you are testing B+ and its lower than it should be, disconnect 1 electrolytic cap at a time until the B+ goes back to normal. Or just replace the electrolytics.

Have fun and enjoy and keep me/us posted with progress. Do not give up!! Not an option.
Best regards,
Matt Davala

[Bill Cahill]

You really need to replace all the electrolytics, and paper caps before you power the set up. That includes ALL black beuties.
I also reccommend you get rid of the black body mica mold caps which are only paper caps in a mica style body.

Then, power it up on a variac of no less that 5A capability.
Let us know what happens. We'll help you.
Bill Cahill

[Phil Nelson]

I would second Bill's advice to replace all of the electrolytic and paper capacitors. After 60 years, they are all bad, and it's pointless to try detailed troubleshooting until they are gone.

In my 630TS, I also replaced four mica coupling capacitors and a few resistors. This article provides details.

http://antiqueradio.org/RCA630TSTelevision.htm

Have fun! The 630TS is one of the best designs of its time and performs well when restored.

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

[Jonathan]

Thanks for the replies, guys. I failed to mention I recapped the whole set, paper, black beauties, micamold, and electrolytic. Either I have made a mistake in wiring everything or the pots could be bad. The 250uF 50V capacitor failed when I powered it up after rewiring the capacitors in the power supply section as I had everything wired wrong. I am almost 100% certain the electrolytic capacitors are wired correctly. The resistance of the pots, should they be around 20 ohms? I'm going to get a variable transformer instead of plugging it right in, this way I can see whats going on without burning anything.

Jonathan

[Phil Nelson]

What capacitor are you talking about, exactly? C225A?

Which potentiometers are you talking about? The vertical and horizontal centering controls (R181, R211) are listed at 20 ohms on my schematic. The vertical hold control (R172) is listed at 1 megohm and the horizontal hold control (R168) at 50K ohms.

"Almost 100% certain" is not quite good enough when you're talking about the polarity of electrolytic capacitors. I would very carefully doublecheck the wiring of every electrolytic against the schematic. Burning up a new electrolytic suggests there is a wiring mistake somewhere.

Phil Nelson

[Jonathan]

Hello Phil,

The capacitor that failed is C225A. I can't remember if I had it backwards, but all the large capacitors all have their polarity correct. I made sure of that because not only are they more expensive to replace but they can fail in a more dangerous manner because they store more energy. I'm almost certain every electrolytic is the proper polarity, because thats one thing I'm careful about.

In place of the two 40uF capacitors that connect directly from the rectifier output to -100V I have an 80uF 450V electrolytic. After the field coil I have a 120uF 450V electrolytic instead of the 40uF and 80uF.

The pots I'm talking about are the horizontal and vertical centering pots. This was my silly mistake not to specify. Since they both measure 20 ohms they should be fine. Hard to believe that most of the set's current goes through these pots. I have to have a wiring mistake somewhere, I just can't find it.

Since C225A failed it was either backwards or there was more than 50V across it. There should only be 5V across it, and if there is more than 50V across it then the bleeder resistors could be at fault. I remember when I did power it up to measure B+ it was unusually high, about 100V higher than it should be, but I also remembered the bleeder resistors tested good. More testing needs to be done.

Thanks.

Jonathan