Rca CTC-25 overview and help

[Electronic M]

If you have HV your fly is still decent. There are a variety of things in the HV cage that can cause that noise. First off the HV cage and the parts inside it need to be VERY clean...Even a thin hard to notice layer of dust can carbonize into a conductive path.
Second: the filament leads between the flyback and the bottom of the HV rect tube and the insulator cup around the base of that tube as well as the HV lead to the CRT and the top lead to the HV regulator can all break down and arc/ develop holes and or conductive carbon tracks fron HV side of the insulation to grounds on the outside of the insulation (I've seen and fixed these issues many times)...Examine it thouroughly with the set on and covers open with little to no room lighting to acertain the exact source of arcing, and if you clean these parts (which you should) examine them carefully.

Third (it has been a few years since I last had a CTC-25) IIRC these molded the top cap of the HV rect tube into the fly HV winding....If the HV rect tube is too physically short it will not seat properly into the cup and arc...Makesure you have one of the taller versions of that tube (different makes made them taller and shorter at different times). Also on RCAs with the HV top cap molded into the flyback there is an issue with the outer rubber tire breaking down and becoming conductive between the cup and the center of the winding. The solution is to peel off the rubber tire scrape away any carbonization beneath the tire and recoat the area the tire once covered with sensor safe RTV silicone.

Another note in the days these sets were new many people in humid climates did not own airconditioners or dehumidifiers, and these sets were designed to handle it. If the fly absorbed too much from being off for weeks/months it would heat up and boil/bake out the moisture sometimes bubbling out a bit of wax too, then normalize and continur to function...If you recoat it before letting it do this maybe leave a small breathe hole or two on the side for it to vent then seal them after it has baked out a good bit.

Also important is making sure your horizontal is set up properly the osc, needs to be adjusted properly as per the sam's proceedure, grid drive/bias at the horizontal output needs to be strong, and perhaps most importantly yout H linearity/efficiency coil needs to be adjusted for minimum H output cathode DC current. All the horizontal adjustment proceedures should be explained in your copy of the Sam's...Preform them.

RCA flys can last indefinitely if you make sure conditions around them are ideal...If they engineered a bit more margin in like Zenith did then you could afford to be more lax with horizontal maintenance.

[ZenithNut]

Originally Posted by Electronic M

If you have HV your fly is still decent. There are a variety of things in the HV cage that can cause that noise. First off the HV cage and the parts inside it need to be VERY clean...Even a thin hard to notice layer of dust can carbonize into a conductive path.
Second: the filament leads between the flyback and the bottom of the HV rect tube and the insulator cup around the base of that tube as well as the HV lead to the CRT and the top lead to the HV regulator can all break down and arc/ develop holes and or conductive carbon tracks fron HV side of the insulation to grounds on the outside of the insulation (I've seen and fixed these issues many times)...Examine it thouroughly with the set on and covers open with little to no room lighting to acertain the exact source of arcing, and if you clean these parts (which you should) examine them carefully.

Third (it has been a few years since I last had a CTC-25) IIRC these molded the top cap of the HV rect tube into the fly HV winding....If the HV rect tube is too physically short it will not seat properly into the cup and arc...Makesure you have one of the taller versions of that tube (different makes made them taller and shorter at different times). Also on RCAs with the HV top cap molded into the flyback there is an issue with the outer rubber tire breaking down and becoming conductive between the cup and the center of the winding. The solution is to peel off the rubber tire scrape away any carbonization beneath the tire and recoat the area the tire once covered with sensor safe RTV silicone.

Another note in the days these sets were new many people in humid climates did not own airconditioners or dehumidifiers, and these sets were designed to handle it. If the fly absorbed too much from being off for weeks/months it would heat up and boil/bake out the moisture sometimes bubbling out a bit of wax too, then normalize and continur to function...If you recoat it before letting it do this maybe leave a small breathe hole or two on the side for it to vent then seal them after it has baked out a good bit.

Also important is making sure your horizontal is set up properly the osc, needs to be adjusted properly as per the sam's proceedure, grid drive/bias at the horizontal output needs to be strong, and perhaps most importantly yout H linearity/efficiency coil needs to be adjusted for minimum H output cathode DC current. All the horizontal adjustment proceedures should be explained in your copy of the Sam's...Preform them.

RCA flys can last indefinitely if you make sure conditions around them are ideal...If they engineered a bit more margin in like Zenith did then you could afford to be more lax with horizontal maintenance.

Thank you very much. Thats all ver helpful and i will clean it up real well. The flyback hasnt melted down or anything. Any special cleaning solutions? Mild soapy warm water?

[old_coot88]

Originally Posted by ZenithNut

... Any special cleaning solutions? Mild soapy warm water?

OMG, NO, nein, nyet!! No telling what kind of conductive residues might get inside.

[ZenithNut]

Originally Posted by old_coot88

OMG, NO, nein, nyet!! No telling what kind of conductive residues might get inside.

Got it!

[Electronic M]

Originally Posted by ZenithNut

Thank you very much. Thats all ver helpful and i will clean it up real well. The flyback hasnt melted down or anything. Any special cleaning solutions? Mild soapy warm water?

For most cases isopropyl (rubbing) alcohol is my preferred cleaning agent. On the metal cage, the HV cables and the plastic HV rect bottom cup (with all wiring and socket removed from cup if the dirt is especially stubborn I will use glass cleaner or goofoff as the cleaner.

[ZenithNut]

Originally Posted by Electronic M

For most cases isopropyl (rubbing) alcohol is my preferred cleaning agent. On the metal cage, the HV cables and the plastic HV rect bottom cup (with all wiring and socket removed from cup if the dirt is especially stubborn I will use glass cleaner or goofoff as the cleaner.

Thank you.

Next time I power the set up I want to watch the current draw. I know the watts on it is 350. So the current draw shouldnt be over 3.2 amps or so once the sets warmed up.

I have a fluke 27/fm. How do i hook it up to watch the current draw? Do I put the negative of the meter to chassis ground and then the positive lead on one leg of the line?

[Electronic M]

Originally Posted by ZenithNut

Thank you.

Next time I power the set up I want to watch the current draw. I know the watts on it is 350. So the current draw shouldnt be over 3.2 amps or so once the sets warmed up.

I have a fluke 27/fm. How do i hook it up to watch the current draw? Do I put the negative of the meter to chassis ground and then the positive lead on one leg of the line?

Line current and horizontal output cathode current have too loose of a correlation to be used interchangeably.

The cathode current can be measured by unsoldering the ground lead from the cathode pin of the h output tube socket then connecting the meter positive current terminal to that pin and the meter negative to ground (sometimes you should put a .47uF cap parallel to the meter ). The current will be in the neighborhood of 170mA to 230mA DC. make sure your meter has a 500Ma DC scale... I'm not familiar with your meter so check it's specs/manual. Also it is preferable to use an analog darsonval movement meter to a digital meter... it is a high frequency pulsed DC current on the cathode. An analog meter will average it well and be the same instrument that Sam's and the factory used to measure that. Some DMMs may get confused by non constant DC... I have not had that issue, but since I have an analog meter I use it instead of my DMM.... it is better for adjusting the efficiency coil for minimum current than most DMMs since it will show you minute changes that a digital display will hide in rounding to it's smallest digit.

One recommendation when you're done measuring the cathode current connect a new wire to the cathode pin, run it above chassis to a good spot to ad a fuse holder, ground the cathode thru a 1/4 amp fuse. Doing this will help protect the flyback from excessive current, and the fuse holder above chassis will also make a convenient current test point for future measurements... all you will have to do is remove the fuse and connect a meter across the holder terminals.

[ZenithNut]

Originally Posted by Electronic M

Line current and horizontal output cathode current have too loose of a correlation to be used interchangeably.

The cathode current can be measured by unsoldering the ground lead from the cathode pin of the h output tube socket then connecting the meter positive current terminal to that pin and the meter negative to ground (sometimes you should put a .47uF cap parallel to the meter ). The current will be in the neighborhood of 170mA to 230mA DC. make sure your meter has a 500Ma DC scale... I'm not familiar with your meter so check it's specs/manual. Also it is preferable to use an analog darsonval movement meter to a digital meter... it is a high frequency pulsed DC current on the cathode. An analog meter will average it well and be the same instrument that Sam's and the factory used to measure that. Some DMMs may get confused by non constant DC... I have not had that issue, but since I have an analog meter I use it instead of my DMM.... it is better for adjusting the efficiency coil for minimum current than most DMMs since it will show you minute changes that a digital display will hide in rounding to it's smallest digit.

One recommendation when you're done measuring the cathode current connect a new wire to the cathode pin, run it above chassis to a good spot to ad a fuse holder, ground the cathode thru a 1/4 amp fuse. Doing this will help protect the flyback from excessive current, and the fuse holder above chassis will also make a convenient current test point for future measurements... all you will have to do is remove the fuse and connect a meter across the holder terminals.

I will buy a 0-500 dc milliamp meter so that I may do that.

For the record though how can i set my meter up to look at the

[Electronic M]

Originally Posted by ZenithNut

I will buy a 0-500 dc milliamp meter so that I may do that.

For the record though how can i set my meter up to look at the

Look at the what?

[ZenithNut]

Originally Posted by Electronic M

If you have HV your fly is still decent. There are a variety of things in the HV cage that can cause that noise. First off the HV cage and the parts inside it need to be VERY clean...Even a thin hard to notice layer of dust can carbonize into a conductive path.
Second: the filament leads between the flyback and the bottom of the HV rect tube and the insulator cup around the base of that tube as well as the HV lead to the CRT and the top lead to the HV regulator can all break down and arc/ develop holes and or conductive carbon tracks fron HV side of the insulation to grounds on the outside of the insulation (I've seen and fixed these issues many times)...Examine it thouroughly with the set on and covers open with little to no room lighting to acertain the exact source of arcing, and if you clean these parts (which you should) examine them carefully.

Third (it has been a few years since I last had a CTC-25) IIRC these molded the top cap of the HV rect tube into the fly HV winding....If the HV rect tube is too physically short it will not seat properly into the cup and arc...Makesure you have one of the taller versions of that tube (different makes made them taller and shorter at different times). Also on RCAs with the HV top cap molded into the flyback there is an issue with the outer rubber tire breaking down and becoming conductive between the cup and the center of the winding. The solution is to peel off the rubber tire scrape away any carbonization beneath the tire and recoat the area the tire once covered with sensor safe RTV silicone.

Another note in the days these sets were new many people in humid climates did not own airconditioners or dehumidifiers, and these sets were designed to handle it. If the fly absorbed too much from being off for weeks/months it would heat up and boil/bake out the moisture sometimes bubbling out a bit of wax too, then normalize and continur to function...If you recoat it before letting it do this maybe leave a small breathe hole or two on the side for it to vent then seal them after it has baked out a good bit.

Also important is making sure your horizontal is set up properly the osc, needs to be adjusted properly as per the sam's proceedure, grid drive/bias at the horizontal output needs to be strong, and perhaps most importantly yout H linearity/efficiency coil needs to be adjusted for minimum H output cathode DC current. All the horizontal adjustment proceedures should be explained in your copy of the Sam's...Preform them.

RCA flys can last indefinitely if you make sure conditions around them are ideal...If they engineered a bit more margin in like Zenith did then you could afford to be more lax with horizontal maintenance.

Hey.

So I got a 0-500 dc ammeter. I have a few things to report in. Im cleaning the hv leads and cage. I am also getting ready to pull the fly cage to re silicone. One thing I forgot to mention is that I did end up loosing vertical but there was still a bit of something you could adjust with the brightness which I imagine was the horizontal.

The boost rectifier diode has gone open. It is listed as a 1n3195. Sr102/X6 has also failed. It is in series with the yellow lead going into the primary of the vertical output. Im having trouble finding a replacement for it. It is a hv rectifier and is listed in sams under General electronics GECR-2. So I will need to replace the boost rect diode and hv diode.

You suggested fusing the h output cathode with a .25 amp fuse. What voltage rating?