Newbie's First Questions RCA TS 721 Restoration

[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 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.

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 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)

[Electronic M]

Originally Posted by Chris K

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

I bought one of those to try a while ago. I can't recommend it because the one I got would regularly black out and come back to normal. Maybe I got a rare defective unit, but if a good portion are like mine (likely for no-name Chinese stuff) it's not a great gamble.

Also IIRC the ad claims it will transmit...It doesn't seem to have the power for anything other than a direct connection and even then was going dark regularly.

[Chris K]

Originally Posted by Electronic M

I bought one of those to try a while ago. I can't recommend it because the one I got would regularly black out and come back to normal. Maybe I got a rare defective unit, but if a good portion are like mine (likely for no-name Chinese stuff) it's not a great gamble.

Also IIRC the ad claims it will transmit...It doesn't seem to have the power for anything other than a direct connection and even then was going dark regularly.

OK I guess I'll stay away for now and rely on the pattern/sound generator and the crappy over the airways digital, converted to analog, signals. On these projects, I try to maintain a conservative, step by step diagnostic and analysis approach but sometimes, at a point of "problem solved!", I want to race to the end game finish line ASAP. I need to concentrate on getting sound next.

[Notimetolooz]

That HV meter looks OK. I haven't seen that model before. Yeah, it could be the capacitor smoothing effect.

A quick and dirty way to check the audio output circuit is to touch the wiper on the volume control with a screwdriver with a finger touching the blade. Don't have the volume control turned down however. You should hear a hum. If this was a hot chassis set you definitely want it plugged into an isolation transformer to do this.
You would need a FM modulated 4.5MHz audio signal to inject to trace the signal further up (from the volume control towards the tuner).
A oscilloscope could enable you to trace the audio from the tuner toward the volume control.
Without those you are left with checking voltages, resistors and tubes, etc.