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Old 11-12-2018, 07:50 PM
ZenithNut ZenithNut is offline
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Rca CTC-25 overview and help

Hello,

A while back my prayers for a tube color set got answered with an rca ctc 25 combo. Its a "halmstead" in walnut veneer modern danish styling. It has a 1972 date code "black matrix" 23valp22 crt in it that tests dam good on my bk 467. Emissions barely drop if you dial the heater voltage down to five volts.

Initial power up was great. However after sitting around my house moisture penetrated the flyback. The last time I powered it up It still had hv but man you could hear it fizzing and hissing in there. Ive since not powered it on again.

Id like to maybe re wax it or seal the flyback with corona dope or rtv silicone. Id also like to get a spare flyback for this set as id like to use fairly often. Used or nos. If used id probably recondition it in a similar fasion to prevent future failure from moisture.

Does anyone have any method of repairing these?

Moyer electronics last a tried was clean out. Same with the early television museum. Ive found one guy in the facebook group vintage television collectors who has one but he wants a $$$ for it which is fine and im completely willing to pony up. I just wanted to try here as well.

I do have the sams and a 1967/68 rca color television manual that covers my set.

I am amateurish as far as experience with tvs go. I have this color set and a bw zenith. Ive mostly done old tube radios and tube stereos. I do have most basic test equipment except a pattern generator and hv probe but thats ok.
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Old 11-12-2018, 11:18 PM
Electronic M's Avatar
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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.
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  #3  
Old 11-13-2018, 11:10 AM
ZenithNut ZenithNut is offline
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Quote:
Originally Posted by Electronic M View Post
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?
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Old 11-13-2018, 11:34 AM
old_coot88 old_coot88 is offline
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Originally Posted by ZenithNut View Post
... Any special cleaning solutions? Mild soapy warm water?
OMG, NO, nein, nyet!! No telling what kind of conductive residues might get inside.
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Old 11-13-2018, 05:33 PM
ZenithNut ZenithNut is offline
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Originally Posted by old_coot88 View Post
OMG, NO, nein, nyet!! No telling what kind of conductive residues might get inside.
Got it!
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Old 11-13-2018, 11:44 AM
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Originally Posted by ZenithNut View Post
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.
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Old 11-13-2018, 01:20 PM
ZenithNut ZenithNut is offline
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Originally Posted by Electronic M View Post
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?
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Old 11-13-2018, 01:40 PM
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Originally Posted by ZenithNut View Post
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.
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Last edited by Electronic M; 11-13-2018 at 01:51 PM.
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Old 11-24-2018, 02:01 PM
ZenithNut ZenithNut is offline
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Quote:
Originally Posted by Electronic M View Post
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?
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Old 11-13-2018, 09:38 PM
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If it is the filament lead/winding that has arced through check the wire's resistance before replacing it. If it is resistance wire it will be more of a task replacing it correctly.

If it is the HV lead that has failed or a non-resistive HV rect filament winding there are a few ways to go...All of them involve getting/installing new HV wire. There are probably vendors online that stock wire with 40KV rated insulation. Non-resistive spark plug wire from an auto parts store may work. I tend to just steal and reuse the HV leads from 1980's and newer CRT sets that folks abandon at the curb. The last option is the only one that comes with a HV connector on the end of the wire. The first two options require you to remove and reuse the existing CRT HV connector from the old wire if replacing the original HV lead to the CRT.
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Old 11-14-2018, 02:54 PM
ZenithNut ZenithNut is offline
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Quote:
Originally Posted by Electronic M View Post
If it is the filament lead/winding that has arced through check the wire's resistance before replacing it. If it is resistance wire it will be more of a task replacing it correctly.

If it is the HV lead that has failed or a non-resistive HV rect filament winding there are a few ways to go...All of them involve getting/installing new HV wire. There are probably vendors online that stock wire with 40KV rated insulation. Non-resistive spark plug wire from an auto parts store may work. I tend to just steal and reuse the HV leads from 1980's and newer CRT sets that folks abandon at the curb. The last option is the only one that comes with a HV connector on the end of the wire. The first two options require you to remove and reuse the existing CRT HV connector from the old wire if replacing the original HV lead to the CRT.

Got it! It wouldnt hurt getting a bpc tv to harvest other parts such as capacitors or resistors.
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Old 11-24-2018, 05:12 PM
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Any of these should work for the boost diode. https://www.mouser.com/Semiconductor...r45Z1yopdfySGT May want to put 2 in series to ensure the replacement can take any possible voltage spike. Radio Shack used to sock a 2A 1.5KV part that I used to replace the boost on my CTC-15 but they ain't a thing anymore. Parts like diodes in sets of this vintage are probably over 3 generations obsolete so it is easier to look up the key specs and spec out a new one than find and trace forward all the missing links in the recommended successor line.

Any voltage of fuse is fine. The only spec that matters for fuses is the current. A you can take a .25A 125V fuse and put it in a device that wants a .25A 250V and vice versa and the device will work okay and the fuse will still blow at .25A current. You probably want a slow blow and not a fast acting fuse...The current averages ~200mA but spikes above 250mA for tiny fractions of each second. A fast act fuse is designed to catch that fractional spike and blow (creating lots of nuisance failure which you don't want) but the slow blow will average out the current and only blow when the average current reaches fault value.
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Old 11-25-2018, 04:20 PM
ZenithNut ZenithNut is offline
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Quote:
Originally Posted by Electronic M View Post
Any of these should work for the boost diode. https://www.mouser.com/Semiconductor...r45Z1yopdfySGT May want to put 2 in series to ensure the replacement can take any possible voltage spike. Radio Shack used to sock a 2A 1.5KV part that I used to replace the boost on my CTC-15 but they ain't a thing anymore. Parts like diodes in sets of this vintage are probably over 3 generations obsolete so it is easier to look up the key specs and spec out a new one than find and trace forward all the missing links in the recommended successor line.

Any voltage of fuse is fine. The only spec that matters for fuses is the current. A you can take a .25A 125V fuse and put it in a device that wants a .25A 250V and vice versa and the device will work okay and the fuse will still blow at .25A current. You probably want a slow blow and not a fast acting fuse...The current averages ~200mA but spikes above 250mA for tiny fractions of each second. A fast act fuse is designed to catch that fractional spike and blow (creating lots of nuisance failure which you don't want) but the slow blow will average out the current and only blow when the average current reaches fault value.
Im gonna go with this guy for the boost diode.



https://www.mouser.com/ProductDetail...%252bUjA%3d%3d

Should work well right?

Also wanting to find a sub for 1n3195 heres the data sheet. There is a NOS 1n3195 on ebay for cheap. That is also an option.

https://www.datasheets360.com/part/d...1594065512865/

Last edited by ZenithNut; 11-25-2018 at 04:39 PM.
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Old 11-25-2018, 07:26 PM
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Originally Posted by ZenithNut View Post
Im gonna go with this guy for the boost diode.



https://www.mouser.com/ProductDetail...%252bUjA%3d%3d

Should work well right?

Also wanting to find a sub for 1n3195 heres the data sheet. There is a NOS 1n3195 on ebay for cheap. That is also an option.

https://www.datasheets360.com/part/d...1594065512865/
First one you may want to put 2-3 in series to ensure against HV spikes/arcover causing it to short, but otherwise it seems fine.


The second diode looks like a common 1N4007 should be a sub for it.

In most tube circuits the important specs for the replacement diode to match or exceed are PIV (peak inverse voltage) and average forward current. The rest usually makes little difference.
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Zenith: The quality stays in EVEN after the name falls off!
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Old 11-26-2018, 07:11 AM
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One last thing is speed ( forgot what they called it ).
If you use a common 3A 1KV rectifier as a scan rectifier it will
blow within a few hrs because it overheats. Cant take the higher
freq. Same goes for in switching supplies.

IIRC boost diodes didnt test like a common diode ? I do remember
they rarely went bad.

73 Zeno
LFOD !


Quote:
Originally Posted by Electronic M View Post
First one you may want to put 2-3 in series to ensure against HV spikes/arcover causing it to short, but otherwise it seems fine.


The second diode looks like a common 1N4007 should be a sub for it.

In most tube circuits the important specs for the replacement diode to match or exceed are PIV (peak inverse voltage) and average forward current. The rest usually makes little difference.
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