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 Post subject: RCA 621TS Restoration
PostPosted: Feb Thu 02, 2017 4:04 pm 
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Posts: 920
Location: Waxahachie Texas
Guys,
I just got this TV. I drove to Houston to get it. Over all in nice shape. It is missing the back though. No rust on the chassis except on the transformer.

The CRT, a RCA 7DP4 test like new! It is in great shape. I'll pull the chassis and see what lies underneath.


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Crist


Last edited by Crist Rigotti on Feb Fri 03, 2017 5:17 am, edited 1 time in total.
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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Thu 02, 2017 5:01 pm 
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Joined: Jan Sun 18, 2015 5:01 am
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Location: Waxahachie Texas
OK, pulled the chassis. There very minor rust spots on the chassis but no big deal. The bottom line is it looks like somebody did a partial resto on it. I should have noticed the fuse holder as my first clue. This one will be a good one that's for sure. Seeing it has been partially restored, should I take the chance and power it up using a variac?


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Crist


Last edited by Crist Rigotti on Feb Sun 05, 2017 12:25 am, edited 3 times in total.
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 Post subject: Re: RCA 621TS
PostPosted: Feb Thu 02, 2017 5:17 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25803
Location: Detroit, MI USA
Great find! You might be OK with a variac if you are careful, there appear to still be quite a few original electrolytics unless those cans have been restuffed. That Mallory can is a decades old replacement. Have to wonder what the last person did and why they stopped?

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Dennis

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 Post subject: Re: RCA 621TS
PostPosted: Feb Thu 02, 2017 5:23 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Fernandina Beach, FL
Very, very nice! Please do us all a favor... put some cardboard securely over that pristine oval electromagnet speaker!!!

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 Post subject: Re: RCA 621TS
PostPosted: Feb Thu 02, 2017 5:46 pm 
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Location: Waxahachie Texas
Mr. Detrola wrote:
Great find! You might be OK with a variac if you are careful, there appear to still be quite a few original electrolytics unless those cans have been restuffed. That Mallory can is a decades old replacement. Have to wonder what the last person did and why they stopped?


I took some time and looked closely at the E-caps. I think they have been re-stuffed. Every E-Cap terminal has been re-soldered and the cans look like the cardboard has been removed and replaced. One even has tape on it.

I just might power it up.

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 Post subject: Re: RCA 621TS
PostPosted: Feb Thu 02, 2017 5:47 pm 
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Location: Waxahachie Texas
Don Cavey wrote:
Very, very nice! Please do us all a favor... put some cardboard securely over that pristine oval electromagnet speaker!!!


Done! Thanks for the reminder.

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 Post subject: Re: RCA 621TS
PostPosted: Feb Thu 02, 2017 5:50 pm 
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Location: Detroit, MI USA
Crist Rigotti wrote:
Mr. Detrola wrote:
Great find! You might be OK with a variac if you are careful, there appear to still be quite a few original electrolytics unless those cans have been restuffed. That Mallory can is a decades old replacement. Have to wonder what the last person did and why they stopped?


I took some time and looked closely at the E-caps. I think they have been re-stuffed. Every E-Cap terminal has been re-soldered and the cans look like the cardboard has been removed and replaced. One even has tape on it.

I just might power it up.



If that's the case, I wouldn't hesitate. The caps which are visible appear to have been done fairly recently.

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 Post subject: Re: RCA 621TS
PostPosted: Feb Thu 02, 2017 7:15 pm 
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Location: Waxahachie Texas
I powered the set up.

First with the low voltage rectifier removed. All the tubes lit up. Then with the low voltage rectifier in but the H output tube plate cap removed. I measured 263 volts! Riders says 265 volts. I received good audio from a local OTA broadcast! Then on goes the H output tube cap connection. No raster. Bummer. Then I remembered the ION trap. Moved it around a little. Nice bright raster!

Hooked up my converter box and now the audio isn't so good on channel 4. But I got a picture! Horizontal sync needs lots of help. I'll bet its a mica cap. All-in-all, this set looks like it'll do good.


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 Post subject: Re: RCA 621TS
PostPosted: Feb Thu 02, 2017 7:26 pm 
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Location: Detroit, MI USA
It looks really good other than being far off frequency on the horizontal. You may be right about a mica cap causing that, I have found a lot of bad ones in RCA's of that vintage to the point where I think it's worthwhile changing all of them in the horizontal and sync circuits and checking any others in circuits that seem to have an operational problem.

You might want to first try setting up the horizontal oscillator following the instructions in the service manual, it's possible the previous owner didn't get that far or didn't understand how to do it.

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 Post subject: Re: RCA 621TS
PostPosted: Feb Fri 03, 2017 3:55 am 
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Location: Long Island, N.Y.
Nice find! - and a really fine example. I bought one of these almost 25 years ago with a restored chassis and it still plays very well. It still makes me smile when I watch something on it. One of the top vintage TV's of them all. Good luck and enjoy!


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 Post subject: Re: RCA 621TS
PostPosted: Feb Fri 03, 2017 4:00 am 
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Joined: Jan Sun 18, 2015 5:01 am
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Location: Waxahachie Texas
decojoe67 wrote:
Nice find! - and a really fine example. I bought one of these almost 25 years ago with a restored chassis and it still plays very well. It still makes me smile when I watch something on it. One of the top vintage TV's of them all. Good luck and enjoy!


Thanks. I feel fortunate to be able to own one.

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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Fri 03, 2017 6:03 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: San Jose, CA USA
That's got to be one of the cleanest 621s out there. Beautiful set!

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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Fri 03, 2017 6:16 am 
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Location: Waxahachie Texas
Tom Albrecht wrote:
That's got to be one of the cleanest 621s out there. Beautiful set!


Really? Wow, I'm stoked! I plan on making this my "show piece" to quote a good friend.

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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Fri 03, 2017 6:25 am 
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Location: Waxahachie Texas
BTW, I'm making a list of all the resistors and capacitors used in this set.

I'll do my usual practice of going up in wattage on the resistors.

I'll use the yellow tubular film caps from Sal or Just radios all rated at 630V.

All micas will be at least 5% 500V rated.

The E-Caps will be 450V or 500V except for the few odd values and much lower voltages. Those will still get at least 250V simply because the leads are thicker and less prone to breakage.

I know there is a door knob cap rated at 500pf but no voltage is given. I'm guessing at least 10K?

Are there any other caps that are rated at a higher voltage? I see C141 a 56pf cap in the yoke. Would this be like a 1KV or higher?

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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Sat 04, 2017 12:38 am 
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Watch your mica voltages. Some, IIRC, are 1000v. 8)

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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Sat 04, 2017 1:03 am 
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M3-SRT8 wrote:
Watch your mica voltages. Some, IIRC, are 1000v. 8)


How can I tell? The parts list doesn't say. Thanks for the heads up.

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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Sat 04, 2017 2:26 am 
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Some are marked or specified in the parts list if they aren't the "standard" 500 volt rating, but others may not be. The yoke cap is typically one with a high rating. You can easily get 2KV or higher disc ceramics in 56pf, look for a C0G temp coefficient.

You probably don't need to replace the doorknob cap, it's rare for them to fail.

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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Sat 04, 2017 5:53 pm 
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Location: Waxahachie Texas
Guys,
I've scanned the Riders info on this TV. It's from Riders TV 1 pages 44 thru 75. I then enlarged the Schematic and Wiring Diagrams and made separate files for those whose size is 36x24 for us old geezers.

I've uploaded them on Dropbox.

The Manual is about 12megs and the Schematic and Wiring Diagram are about 1meg each.

https://www.dropbox.com/s/awm0knizurcrz ... l.pdf?dl=0
https://www.dropbox.com/s/52cxfm9klnrap ... 4.pdf?dl=0
https://www.dropbox.com/s/ajfa53b9r97bx ... 4.pdf?dl=0

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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Sat 04, 2017 7:13 pm 
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Location: San Jose, CA USA
Another good place to get service literature is the ETF website: http://www.earlytelevision.org/tv_schem ... s_rca.html

There is the Rider manual, a service manual for this set, and the owner's manual.

Your schematic and wiring diagrams above are nice, since you've got it all on one page with good resolution.

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 Post subject: Re: RCA 621TS Restoration
PostPosted: Feb Sat 04, 2017 11:10 pm 
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Location: Waxahachie Texas
Mr. Detrola wrote:
Some are marked or specified in the parts list if they aren't the "standard" 500 volt rating, but others may not be. The yoke cap is typically one with a high rating. You can easily get 2KV or higher disc ceramics in 56pf, look for a C0G temp coefficient.

You probably don't need to replace the doorknob cap, it's rare for them to fail.


M3-STR8 and Mr. Detrola,
Thanks for the heads up on those micas. I know the door knob cap is probably at least 10Kv, but the yoke cap looks like it could be 800V or 2000V using the RMA/EIA code. I've included a picture of it.

Other than those 2, the parts list doesn't list any voltages or any warnings on the mica caps. I know M3-STR8 has restored a 621TS so he has experience on this TV.

So, is there any other mica cap that I need to be aware of a higher voltage rating above 500V?

Thanks for your help and comments.


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