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.

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?

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

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?

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.

Got it!

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?

Do"h

I want to look at the overall ac current draw the set is using. I checked my fluke meter and it tops out at 320ma so an analog dc milliamp meter is on its way.

On tube sets that test is much less informational than solid state. A meter that can't measure 5-10A AC can't directly measure the line current the set draws. (also some DMMs that can do 10A only do DC and some only do AC so knowing which the meter can do is important)....

All that said there is a way to indirectly measure the AC that set uses with your present meter (assuming it has an AC volts range) get a 5W or higher, 1 OHM power resistor place that resistor in series with one leg of the cord (can hack up an extension cord to do this (and make a universal adapter) ) then with the meter in AC volts range measure the voltage across that resistor...You can then compute the approximate current using ohms law: I=E/R= measured voltage/resistance...Given resistance should be 1 OHM that means measured voltage should be approximately equal to the current flowing. The accuracy of the resistor, the accuracy of the meter, where you connect the meter along the wire will all introduce some error to the measurement, but it should give a decent approximation.

My fluke meter can go up to 10 amps ac/dc
Youve been really helpful so far. Cleaning out the hv cage and all the leads. I swore this hissing noise came from the back side if the cage. It will be a while till I get that dc milliamp meter in the mail.

One thing i forgot to mention is that one of the power resistors has been replaced on the chroma board. Also Ive been told theres a trace along that board that tends to fail. Fortunately mines in good shape. All ive done to it to add on is replace a few e caps and reflow the ground stags. Some have mentioned hard wiring the ground with a wire.

To touch up on your earlier post the ctc 25 does use a cup ontop of the flyback where the plate cap of the hv rectifier sits inside. I will wrangle up a few and see if it helps next time i power it up with a ammeter telling me what the cathode current.

If any of the wire insulation is at fault from breaking down (and this IS a high hour set) what would be a good replacement? I imagine regular old heat shrink tubing wouldnt be good enough for the 24kv..

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.

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?

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/

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.

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:smoke:
LFOD !

With the virtual extinction of 60Hz linear power supplies most new rectifier diodes can handle at least horizontal rate switching. Even the humble 1n4007 is found in switch mode supplies these days. I've used many normal silicon rectifiers as boost and convergence doide replacements in tube sets had good results. The original boost and convergence diodes were selenium for fast switching...If they had the modern fast switching silicon diodes we had now back then they would have used them instead of seleniums.

Still it is not a.bad idea to convert switching time to seconds then take the inverse to get frequency and make sure that frequency is higher than that of the waveform applied.

I went to my local electronics shop and picked up a 1n4007 and a 1n5408 for the replacements

Electronic Memory.

Ive peeled the brown tire off completely. Theres this rubbery kinda pink stuff under it. I imagine that has to go too right?

There are no visible signs of conductance on the tire of the fly. There is one tiny spot where one spec of the winding is exposed but I think that only happened peeling the tire off.

Of course ive successfully removed the fly cage for cleaning too. I have almost everything short of a fuse and fuse holder I forgot to get when I was in town.

That pink stuff is silicone. If it is blackened or loose pull it off, otherwise it is fine to leave it be.

If you exposed the winding then you may want to check continuity before applying fresh silicone... if you somehow nicked a lead open it will be much more of a pain to find and fix after you coat it.

BTW if you want to see the process of coating it I have pics of a CTC16 fly I did a few years ago in a thread here on VK. Shango66 on YouTube has some videos of this too.

I ohm"d out each winding ie 1 to 2, 2 to 3, and so on. Everything was in spec. Looks like a piece of wax paper came off with the silicone.

All the loose old silicon is gone. So ill look at your thread.

Btw I love shango066 s channel.

I dont know if this was the source of hissing but the non painted metal shield surrounding the 6el4 shunt regulator, there is a clip to hold the hv leads and theres a "shadow" almost burnt into the metal. As in its really clean were the leads were resting against and browned on the edge.

Im having trouble finding your thread. I have all the old silicone off. I imagine im hust gonna put a nice even layer on right?

Pretty much.

It is this thread for what it's worth http://videokarma.org/showthread.php...=CTC-16&page=6 Some of the pictures are gone... IIRC I deleted them to make room when my Photobucket filled back before they instituted hosting ransom... Normally I try to preserve resto info I post but the cat I did that work for flaked out on payment he owed and I was a bit angry.

I have the sonic the hedgehog blue silicon evenly smoothed over the fly. The new diode has been installed, and ive disconnected the cathode (pin 3) of the h output tube from ground. I soldered a jumper from ground to the top of the chassis and another jumper to pin 3. My am meter will go imbetween these two points.

To be honest im sorta nervous about this. I just really wanna see it work. Ive worked on a zenith bw tv set and successfully restored both my fisher tube receivers. I think im nervous cause its color.

I know the silicon isnt really conductive when its wet but it is drying. Will be ready to fire up soon

I hooked everything up and the cathode current steadily rose up to 200ma and then kept going towards 300. I unplugged the h output cap and it dropped to around 40ma. If i touch the h output cap to the tube it goes up towards 300 but then it started backing down to around 250. Tweaking the hori linearity coil had some effect. If I touch the plate cap you can hear the hv jumping. My tube tester doesnt test compactrons so I sont know if its shorted or not. I might have an extra. I had all the controls turned down so I dont know if there was anything on the screen.

No smoke from the flyback and theres hv

*im not sure if the h output tube is shorted.

It got really freaking hot too

OK So I did not have the cathode and filament tied together. I fixed this and the cathode current is a bit more normal now. I was going to adjust the hor linearity coil so I put the plate cap back on top of the h output tube and BOY the hv got me. I will say it doesnt have near as much as a bite as getting bit by my 87 TBird doing the timing with an old timing light.

Tom/Electronic Memory when it powers up theres a "sound step" noise squeal and this squealing noise. Is that the horizontal running off frequency?

I had it on. This time it didnt squeal and it settled around 220ma then slowly lowered to 190 then slowly moved to 200ma then it sounded like something came up and the meter rushed up to near 300ma. Turning the coil didnt really do much is seamed. Of course when it jumped up i turned it off

Squealing is usually the osc off frequency. Not sure my imagination can do much with"sound step" though.

Do you have an oscilloscope? If you do you can use that to adjust the osc with the output pulled. If not get video on the screen and some vertical deflection and adjust the H osc according to the procedure in the Sam's photofact for your chassis. A minute or so of ~250mA shouldn't kill the flyback, much longer is not advisable though.

Yes I have a o scope. Sound step I mean like almost a quick step of different pitch squealing. Like playing EADG of a guitar then it stabilized. Last i powered it on the squeal went away. Im not getting anything on the screen or sound. Im gonna make sure all the tubes are socketd down

The wave on the 100ohm resistor to pin 2/6 of the h output tube is really "steep" compared to the waveform on the sams which has a really broad curve thing. im definitely turning the core and its not changing the wave form.

The wave form is much narrowed then the rather broad looking wave in the sams. Turning the slug has no effect on the wave form. Im looking at the sams thinking why that would be

Since I my CTC-25 info went with my CTC-25 to its new owner I'm kind of flying blind here.

Which slug are you turning? If it is the linearity slug that will have no effect on the frequency and probably very limited effect if any on the H out grid drive waveform.
Are you adjusting the slug with a proper plastic hex adjustment tool? If you use a metal hex key for adjustment you will crack your slug (which will make it feel like it is turning when it is not) in short order.

The general procedure I go on for a rough osc adjustment is this: Connect scope to a composite video source (a VCR or DVD showing a blank screen is nice for this) and tune the scope to show 1-3 cycles of horizontal sync/video lines, count the number of divisions between leading edges of peaks, leave scope H/time settings exactly as they are from here on, connect scope to TVs horizontal osc test points adjust the horizontal osc trans top slug for the correct width of the waveform (make sure peaks are same distance apart as you measured with composite video) then if needed adjust the bottom slug for wave shape in the osc section (don't worry about output grid yet). Generally, I rough in the frequency and wave shape then follow sam's instructions when I have a picture on screen to optimize things. If after adjusting the osc the waveform at the grid of the output tube looks bad check the components between the osc and output.
The osc trans will be next to the H osc tube (usually a 6CG7) on the sweep PCB...There are two slugs in the osc transformer a top (usually freq) and a bottom (usually shape) and they may interact a bit...Some RCAs did a dirty trick and did not give a bottom access hole in the bottom of the board for the lower slug...Instead, to adjust it you had to have a plastic alignment tool that only had a 1/4" or less hex section on the end of the shaft and was narrower than the hex over the rest of the shaft. That tool made it possible to adjust both slugs separately from the top. You can still find those alignment tools for sale online.

One thing to watch out for on RCA per your explanation of the stepped freq behavior is bad PCB solder joints...The worst spots are on the H osc, H lin/efficiency coils, and the board ground to chassis ground joints, and tube sockets that all have a lot of mechanical stress on them. If they crack you will get weird intermittent behavior that makes no sense. I will often reflow them whenever I have weird symptoms. A 75W or higher gun or preferably soldering iron is best for the grounds...Everything else, use a more tame iron for.

That is all the wisdom I've got for tonight. I'm going to bed. Good luck.

I was tunning the h efficiency coil so that makes sense why there was no change. I do not have a plastic hex. I have an "Ifixit" tool case with the proper size hex end but it is metal.

I dont have a vcr BUT i have a lot of old cartridge based nintendo and sega video game consoles I can use for a composite source. So youre saying to fire up the scope attatched to a blank composite source and then dial in the scope to get a wave form then keep the scope on those setting and attatch the scope to the tv and adjust the h slug to match the wave from a blank input setting from the composite signal of my choice?

I might end up doing some reflowing. I had audio and video before the chassis went on the bench. Now theres no sound or video. All I did was replace a few ecaps and re silicone the fly. Thank you for your help Tom.

Definitely get a plastic alignment tool and stop using the metal one before you crack your slug... I've been there done that, and can say removing a crack slug without destroying the coil can be a royal pain in the butt... sourcing a new slug can be tricky too.

The only thing you will need to change on your scope is the vertical voltage scale. Composite video is about 1vpp and h osc waveforms in tube set are on the order of 50vpp...
How new your game system is can be important if you plan to use it as a H frequency reference. Older game systems used 240p rather than 525i. That change shifted the horizontal frequency a bit, and while most sets can sync to it I'm leery of using some random spec a programmer came up with because they were too cheap/reasource strapped to create a proper NTSC spec video source.

If you lost video and sound together you probably want to check tuner and IF systems. Wiggle tubes and if you get noise that stage and everything between it and the video detector diode are fine. In some cases the IF lead to the tuner will open or go intermittent... I have a CTC15 clone where the tuner and it's IF lead are permanently connected to the main chassis with soldered wire. The point the IF lead solders to the tuner has no strain relief so when I pull the chassis the center conductor of the IF lead tends to break off of it's tuner solder post... killing both picture and sound.

Do you have raster? If not check your boost voltage. Troubleshooting, adjustment and repair all get easier with the screen lightning.

Now that i think of it i dont have the antenna or uhf/vhf cables connected. Ill hook the tunner up as needed. I ended up using my super nintendo to get a nice wave form 9 divisions wide and 30 high. The sams says theres a waveform off pin 8 of the h osc tube. It was thinner and super high/long, not sure what exact words to use to describe it. Ill get a plastic hex as suggested. Since I wont be tunning the slugs with a metal hex ill do as much more as i can in this set then im gonna get (a much simpler) zenith bw tv going chassis 17T20.

There's little point in doing the scope work till you have the correct adjustment tool. Another good reason to not use a metal adjustment tool is that the magnetic properties of the adjustment tool have the same effect as the magnetic properties of the slug.... simply inserting a metal tool or removing it has the same effect.on the circuit as turning the slug some amount...so if you get an adjustment perfect with the metal tool then as soon as you removed the tool the adjustment is thrown off of that perfect setting.

The "height" ie signal amplitude and wave shape of composite video and h osc waveforms are going to be radically different... the goal is to compare the synch frequency (width between pulses) and h osc frequency to allow calibration of osc frequency to a known reference.