Newbie's First Questions RCA TS 721 Restoration

[Chris K]

Another dumb question...I do have a high definition antenna for over the air digital broadcasts and a converter to analog box. Is there a way I can use this setup to play computer video through the analog RCA?

[Electronic M]

Your tuner should have detents. IIRC around then RCA was using a ball bearing and spring to make a detent and if the ball falls out you loose detent.

A DTV converter box alone won't work. You can use an HDMI to ATSC modulator if you want (it's expensive, but has it's advantages). In this video I discuss doing just that in my set up. https://m.youtube.com/watch?v=hKjt3x4WtWU

An HDMI* or VGA to composite video converter and RF modulator is cheaper and will also work. * DVI, Display Port, and HDMI use the same basic electrical interface so you can buy a cheap dumb DVI to HDMI or display port to HDMI cable if your computer doesn't have HDMI output.

[Chris K]

I think I can fix the tuner with a round head bolt and a nut mounted on the spring steel holder. Picture is getting better!

[kvflyer]

That looks more like it! You probably have it licked now. "Good on 'ya!"

[Chris K]

Thanks... gettin there. Thanks to VK I've gone from a blank screen to this in less than a week! The original capacitor carnage is below.

[Phil Nelson]

Originally Posted by Chris K

Picture is getting better!

Excellent -- looks like you are in the home stretch.

I don't know if you ran across it, but my website has an article describing how I restored my 721TCS (same chassis in a console cabinet):

https://antiqueradio.org/RCA721TCSTelevision.htm

These sets can definitely make a fine picture.

Enjoy!

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

[Chris K]

Absolutely Phil...your site was the first one I saw when investigating and researching this restoration. I love the picture grab from GWTW! Good Ole Daddy O'Hara half nuts from Lee's surrender at Appomattox.

My next task is to start running down a couple of remaining issues. First, it looks like I'm only getting around 4Kv on the HV anode. It's enough to give it a decent picture since it's only an 8.5Kv CRT but I'm kinda stuck as to where I go from here. BTW, the HV measurement was done on the anode while it was disconnected from the CRT. IDK if that makes any difference. The second issue is sound. There isn't any. The speaker tests fine and the AOT ohms out perfectly. I am getting some funky voltages on the audio output tube. I can post on them more specifically this evening.

Thanks for chiming in Phil. Best
Chris

[Chris K]

Originally Posted by Electronic M

Your tuner should have detents. IIRC around then RCA was using a ball bearing and spring to make a detent and if the ball falls out you loose detent.

A DTV converter box alone won't work. You can use an HDMI to ATSC modulator if you want (it's expensive, but has it's advantages). In this video I discuss doing just that in my set up. https://m.youtube.com/watch?v=hKjt3x4WtWU

An HDMI* or VGA to composite video converter and RF modulator is cheaper and will also work. * DVI, Display Port, and HDMI use the same basic electrical interface so you can buy a cheap dumb DVI to HDMI or display port to HDMI cable if your computer doesn't have HDMI output.

Hi Tom...would something like this work? I do have an HDMI output port from my computer.

https://www.amazon.com/HDMI-Converte.../dp/B07W58PNPP

[Notimetolooz]

You probably didn't need to replace the rectangular mica capacitors. Electrolytic and paper dielectric are the ones that are important. You can mess up the alignment if some mica or ceramic caps are replaced.

Some computers (probably older) have an analog video output.

The analog video output would have to go through a RF (NTSC) modulator to put it onto a TV channel that you can feed into the antenna terminals.

How did you measure the HV? It could be that your measurement method could be loading the HV more than the CRT.

[Yamamaya42]

Originally Posted by Notimetolooz

You probably didn't need to replace the rectangular mica capacitors. Electrolytic and paper dielectric are the ones that are important. You can mess up the alignment if some mica or ceramic caps are replaced.

Some computers (probably older) have an analog video output.

The analog video output would have to go through a RF (NTSC) modulator to put it onto a TV channel that you can feed into the antenna terminals.

How did you measure the HV? It could be that your measurement method could be loading the HV more than the CRT.

I was thinking the same thing, the mica domino capacitors did not need to be changed, however the one on the far left may be a paper “wolf in sheep's clothing” type domino.
There were 2 in my FADA set that I thought was mica, until one of them decided to let me know that they were paper by exploding and making a big mess!

[Chris K]

Originally Posted by Notimetolooz

You probably didn't need to replace the rectangular mica capacitors. Electrolytic and paper dielectric are the ones that are important. You can mess up the alignment if some mica or ceramic caps are replaced.

Some computers (probably older) have an analog video output.

The analog video output would have to go through a RF (NTSC) modulator to put it onto a TV channel that you can feed into the antenna terminals.

How did you measure the HV? It could be that your measurement method could be loading the HV more than the CRT.

I measured the HV with a B&K 0-40kv range test probe with the kilovolt meter on the probe, grounded to the chassis...actually I tried grounding to the chassis and the HV cage and the readings were the same.

Yes, the dark dominos are paper but, I changed the micas for 2 reasons...they were a bit out of spec and Phil, who graciously chimed in above, changed the micas in his restoration. The micas I replaced were in the horizontal trimmer area for frequency, output and lock. Is it possible to change the HV output by moving the horizontal output adjustment?

[Chris K]

Originally Posted by Yamamaya42

I was thinking the same thing, the mica domino capacitors did not need to be changed, however the one on the far left may be a paper “wolf in sheep's clothing” type domino.
There were 2 in my FADA set that I thought was mica, until one of them decided to let me know that they were paper by exploding and making a big mess!

The micas were primarily in the horizontal frequency, output and lock trimmer section. They were out of tolerance but not by much. Phil changed his so I changed mine!!

[Chris K]

Originally Posted by Notimetolooz

You probably didn't need to replace the rectangular mica capacitors. Electrolytic and paper dielectric are the ones that are important. You can mess up the alignment if some mica or ceramic caps are replaced.

Some computers (probably older) have an analog video output.

The analog video output would have to go through a RF (NTSC) modulator to put it onto a TV channel that you can feed into the antenna terminals.

How did you measure the HV? It could be that your measurement method could be loading the HV more than the CRT.

Here is the B&K

[kvflyer]

Just a thought, if the CRT is not connected, it can't act as a capacitor (aquadag coating). Could that cause the voltage to appear lower? You know, if you have an open filter capacitor, the unsmoothed voltage would be lower.

[Chris K]

Originally Posted by kvflyer

Just a thought, if the CRT is not connected, it can't act as a capacitor (aquadag coating). Could that cause the voltage to appear lower? You know, if you have an open filter capacitor, the unsmoothed voltage would be lower.

I changed all the filter caps...all new electrolytic caps (Nichicon)