Restoring a 1963 Admiral ctc-12 clone
 

I decided to tackle this set , I can't believe how many tubes are messed up in it with shorts/gas and grid issues , amazingly one 6GH8 reads ok , I've replaced most of them with nos tubes ,there was a 2av2 in the 1v2 socket , would that work ? it was bad anyway so I put a 1v2 in.

the circuit breaker was replaced but instead of being installed wires run out to one mounted to the back , also theres an electrolytic can with wires running from the original wires , it just lays on the inside side of the set , these are things I will have to properly repair.
when and if I get it up and running should I adjust the hv control for less voltage to anode so the fly doesn't get pushed as much as it could be ?
what should the anode voltage be roughly ? I used to know but don't remember , I don't work on color sets enough.
also the selenium on the convergence board should I be worried about it ?
there are so many orange drops in it that I wont touch them unless theres some kind of issue in that section.
anything I should be expecting or know about like the power diodes or other issues ? I don't see a degauser wire around the crt , just glanced at the schematic and don't see one
mike

I think the anode voltage should be in the 22KV range if everything is working correctly. Check your input thermistor (inrush limiter) if you have one. The leads like to come apart from the body of the thermistor. The resistance cold should be on the order of 10-15 ohms or so.

adj the HV will not do much to the flyback as it uses a shunt tube, and if working it just absorbs the excess current. there is an eff coil on the chroma board that should be adj for min current, this is all covered in the sams.

Leave the Se pack alone on the convergence, I have found that most of the time they are fine, you will know if the convergence does not work.

the 2 vs 1 in the focus circuit, the 2 was used in the later CTC-16 the 12's had a resistor in the filament circuit of the focus. If you see a resistor on the focus tube socket then it prob needs the correct tube the 1V2.

These sets often work just fine as found, I have several that have the orig filter caps. Sound like at least one may have already gone so I would at a min restuff that one. The film caps in the vertical circuit sometimes give trouble they are HV types 1600 IIRC. so if you have vert jumpiness or odd vert behavior then those should go. .0082 is the biggest offender as it takes the most punishment. Right off the plate of the vert out.

i will replace any film caps that are not orange drop or brown drops just to be safe , I just did the .001 at 2000 volts with a Sprague orange drop rated at the same value and voltage , the original is one of those that are in like a ceramic tube and didn't want to chance it but will test any that are removed for the fun of it just to see if they are leaking, I think there is another 2000 volt cap in the audio , I think I have a replacement for it too.
I never attempted power up due to the issues I already mentioned ( circuit break , electrolytic ) plus with all these tubes that are not good it really would have not been pretty , the 6dq5 was in bad shape so its hard to say if it would work with it anyway.

I don't think there is a thermistor in the set but will check anyway

the ones in the vert may be bad even if orange (and prob if brown). the symptoms will be poor vert lin and maybe jumpiness.

The .001's are good to replace, I read somewhere the one on the primary side of the vert out is there to decouple any horz noise that is leaking back from the yoke windings.

I think you are right about the thermistor, I don't recall seeing degaussing circuits until the 16's

If you care to you can add a jumper wire off the cathode of the horz out tube. I routinely do this to make cathode current checks easy. I just snip the lead that goes the ground and add a length of insulated wire to that pin on the tube socket, then lead it out to the back of the chassis with a spade type connector that can be screwed down after checking current.

I also will replace the caps that are often in the AC inter lock, may be bumblee bee in there across the line.

There are 3 caps in the grid circuit of the 6GU7 diff amps. One of them that rest right between the tube and a power resistor is almost always weak when tested on a old school cap tester. If I have the chassis out I generally replace all 3 of those .01's.

one last thing to check, there are a couple jumper wires on the chroma board often are rotten and will break right off. If this happens the screeen will be tinted one solid color like the screen drive is turned wide open. I have seen a lot of these break so its a common problem. You will know for sure if one of the big power resistors is cold on chroma board (one of the wires feeds thru that). They can look OK but still be broken. A slight tug upwards will reveal that.

Ok you guys would know this has a 21FBP22 in it not the 21FJP22 as listed in the schematic / sams , is this an older crt ? any advantage or disadvantages ? it looks like admiral date code 63-11
ok I will replace the caps in the vertical section as suggested , the set doesn't use 6GU7 tubes ,uses 6GH8 chroma bypass amp/color killer , 6JU8 chroma sync phase det killer det , 6GY6 z demodulator , 6GY6 X demodulator , 12BY7 Video out , 6EW6 burst amp , 6GH8 chroma reference osc , 6FQ7 b y amp r y amp , 6FQ7 horz blanking amp g y amp , that's the color board.
the jumped electrolytic that I mentioned had a hand written installation of 1979.

heres a question can I replace that electrolytic 160uf @ 250 volts with a 250uf @ 350 volts or a 470uf @ 250 volts or is going too high going to mess things up ?

he did something interesting , its a multi section can and all the values were connected together to make 140 uf which is 20 uf too low but it must have worked or was close.

what pin on the horz out are you referring to and if it is too high I have to change some resistor / resistors ?

oh yeah the .0082 @ 1000 volts could I put a .01 there ?
mike

The CRT's are the same. One has a bonded safety glass and the other one does not. Some have a clear safety glass and others are frosted and tinted. You could use a 250uf cap but would be better to use something closer. The voltage rating of 350 is good.You can always go higher but never go lower.What the tech did was OK.The tolerances of those can caps are usually 20% either way

surprise surprise surprise as gomer pyle would say , I tested the 3 capacitors I removed , the .001 @ 2000 volts is ok , the .047 @ 600 volts is ok and the .01 @ 400 volts is ok , so looks like replacing others would be a waste but I will check the ones that are known to go or be bad , looks like I'm just going to do the electrolytic capacitors since one was bad in 1979 I wont chance the others and slowly power it up , I will check power resistors and anything that might not look right before doing so.

so this set has a non bonded safety glass (21FBP4) ? , if that's the case it sure is tempting to clean it but a lot of work , theres is a couple spots that look odd , I thought maybe it was cataracts but this may be just dirt , hopefully it's not annoying while watching .

sorry I don't have pictures and step by step on this restoration.

mike

I would stick with the 0082 if that is what is there, and go high on the voltage, so if its a 1600, I put in 2000, the price is about the same and the fit will be better anyway as old caps are larger than new ones.

sorry about the 6Gu7, I should have checked, the caps that have been bad on those is the .01, its right behind the 6FQ7 that is close to the middle of the board (not the one on the end), but I replace them all anyway. I can say that its hard to tell if there was any change (the bad test was the fuzzy eye opening on the value check, leakage tested fine).

I presume you are checking the caps with a old school cap tester that can apply working voltages, those little hand held DMMs are worthless when checking caps since the failure mode generally does not show up at the low voltages they use. I replaced the .001 simply because my cap tester maxed out at 450v so I could not check them at the rated voltage.

Most of the time the film caps are ok, The ones that have given me trouble in the past have been those few in the vert circuit. I generally dont do mass recaps on sets of this era without at least trying to see if it works (that way you have a base line to compare to).

The issue on mass recaps is the introduction of user error, if you are good at diagnosis then you can generally find the problem but if not you can make a real tough dog out of what may have been a working set. RCA with its PCB make wiring errors hard to do, but there is still the possiblity of value errors, .001 for a .01 as an example.

What I do is when replacing (that I think may be a problem) is remove the cap, test with the cap tester, if bad I will leave the cap tester alone and check the new cap going in (always a good idea, I have had bad brand new caps). By leaving the cap tester settings unchanged I compare the value that came out to the value that goes in (even bad caps will give an indication of value on the old school cap tester). If I do not have to adj the settings much then that is a double check that the value is correct (besides just reading the cap values). So you not only check the part going in (value and leakage) but also confirm the value is correct. This is esp helpful with the new numbering like 103 for .01 etc...

yes old tester and applied voltage to caps , I will do the vertical caps to be safe , one of the annoying things is to pull something apart , put it all back together to find you have to open it up all over again.

one board (either the color or horz vert ) clearly says rca on the underside , also the sams where it points out parts locations in photos shows a color board that has bigger tubes then whats inn the set and schematic and tube location in the sams.

On the non bonded CRT's, they have a rubber gasket around the edge of the safety glass that oozes an oily substance that gets on the CRT face and inside of the safety glass. Unfortunately, the only way to clean it is by removing the CRT. I did it with my '67 Admiral roundie because it bothered me but it may not bother you. I would just leave it to very last after you get it running.

JC what kind of cap tester do you have? have not seen one that can do 2Kv in the leak test.

On higher hours RCA clones I'd check all the caps on the color board. I have seen some sets where a good portion of the orange drops there were bad, and the .01 orange drop nearest a tube actually was split open!....It was not shorted, but it did not have a defined value when tested.

I will check other caps to be sure , the previous owner did install a fan that looks like it might be from a record player so it was kept cooler while running then sets that didn't have a fan , I guess it would explain why there was so much dust under the chassis , normally I find it cleaner there , this fan pushed air around in there so it helped keep the air circulating , the cover to the hv / fly is not present , I'd guess to help keep things cooler, I don't see any signs of things being over heated, I remember years ago when fixing sets for neighbors seeing caps that were orange drop near a tube and they had that burned look on the side .

I guess I'm going to have to use the 470uf in place of the 160uf or keep the replacement in and check if it gets warm or hot , I don't have anymore caps to replace with unless I waste a 100uf @ 450 volts hooked to two 33uf caps or a 47uf , the circuit only requires a 250 volt cap so I'd be wasting the 450 volt cap .

If that 160uF cap is part of a voltage doubler circuit (which was common around then) I would recommend keeping it the same value as the other doubler cap...I'm fairly sure there is a reason why all doubler circuits I've seen use the same value for both caps.

well here is the latest , going through resistors and not finding anything really bad off except for one that is 150 ohms and its 230 ohms and another that is 1k and it reads almost 2k , haven't gone through the capacitors but if they are like the ones I removed I expected to have leakage and they didn't the others may be ok too but testing will show for sure.

mike

went through the capacitors in the vert horz board , they were all checking good , I almost gave up but then found a .47 with minor leakage that goes to the vertical hold control that changed my mind and the other which had a good amount of leakage was .1 in the agc section, I did find it interesting that on some when I de-soldered one leg of the cap to test it the end still connected would move a little on the board , I even found this to be true of a resistor that I never heated the pins , is it just because the solder joints are old or is it just because some weren't strong from the factory ? any ideas ?

oh yea the ctc12 clone how i remember, in my sears silvertone 1963, changed so many caps and it still has issues. maybe one day it will be close to perfect which these sets were never perfect but better then it is now. if its not verticle its hv and if its not all those its cant get the color just right, ahh one day . good luck with your set. those solder joints can move because the joint is old and needs to be reflowed or the foil trace has come loose from the board it self and you dont want to tear the foil otherwise you will be putting jumpers in to correct the connections of the traces that broke.

there were a couple others I found , a ground to the board of the convergence was loose , a ground to board somewhere else was loose , so as I go through the set I will be checking connections , the very few terminal hand wired ones seem ok , boards were a mistake .... perhaps you just need to redo all the solder joints on yours?

mike

Well I'm pretty much done going over the set , seems that the orange and brown drops are ok except for a couple I replaced , I didn't touch the if boad , I figure if theres a problem I will but left it alone , theres only one orange drop on it .
so as soon as I reconfirm that resistors I wasn't sure if they were ok or not I will give it a slow power up on the variac and then hope it works and will wonder how much adjusting may be needed as far as convergence.

what was the pin on the horizontal output tube I should measure the voltage on and what the voltage should be ? ( probably says it in the schematic )

mike

On the old RCA chassis, it's not uncommon to get fractured solder joints. I ran into this on a Silvertone combo set I worked on a couple of months ago, which had a couple of bad connections on some jumper wires that I needed to re-solder. Fractured solder joints can be caused by either repetitive mechanical stress or by thermal cycling (typically thermal cycling in an old TV set). Bad solder joints are also common where the PC boards solder to the chassis to pick up ground. Be sure to check these as well.

Well it is up and running , when slowly powered up it came to life , needs adjustments as you can see with the convergences , when it came on the picture was a blur , I tried another 1v2 and still a blur , I tried the focus and almost got a clear image but still blurred with the focus adjustment rotated as far as it would go in, so I then said what if I try the 2AV2 that was in the set to begin with - bingo a better image that focused well , odd since the tube chart and sams says 1v2 and in the set laying loose was a 1v2 admiral tube , this 2av2 doesn't even test well but seems to be working , the fly gets hot or warm , not too hot to touch , should it get warm/hot ?
there is also way too much green , tint has to pretty much go all the way to one side to get sort of normal colors , should I try the green drive or the green screen ? I can tell you the black and white image is pretty much grey that's why I'm unsure which to decrease for better tint .
is the blue issue the blue lateral or the convergence board ?
any other tips ?
the pictures show better then what can be seen in person as far as the color goes , the image is much sharper and detailed in person then the pictures show, looks like it has a clearer more detailed image then my zenith did or my friends silvertone.

thanks

a good set up and your done!crt looks ok so now just to a purity and convergence procedure and enjoy.

i don't recall purity tests , I will have to look it up , its on my color generator along with the dots and boxes but I don't recall what I'm supposed to do on the set , the screen or drive controls, convergence I know except it may be lateral needs adjustment too , wont know till I adjust the convergence board

check purity 1st before moving on to ANY convergence (static or dynamic).

just watched a couple youtube videos on this subject, I will try to do everything without moving the yoke and see where I get , if worse comes to worse I will move the yoke to make sure red is centered and go over the whole thing again , now with the these screen adjustments I should take the weakest color and turn it up as much as it will go and then take the others and make a uniform picture closest to grey as possible correct ?

in the past when working on color sets all I had to do was minor adjustments on convergence upper right , lower left etc

mike

On the screens: turn brightness to min, flip service switch to collapse vertical to single horizontal line, turn screens down until line goes away, turn up red until a faint red line just starts to appear, turn up green until line becomes yellow, turn up blue until line becomes white, return service switch and brightness to normal then check image with color off to see if gray scale stays gray. If it is tinted adjust color drive controls for proper gray scale.

Your blue lateral is indeed off in the pics. Use the static adjustments on the convergence yoke and the blue lateral to eliminate color fringing in the center of the screen. If there is objectionable color fringing away from the center of the screen use the dynamic adjustments on the dynamic convergence circuit board to reduce them as best you can.

If the gray scale is good and the tint control does not have enough range then the drive and screen adjustments are NOT the problem; there are problems in your color demodulator that may or may not be solvable with available demodulator adjustments.

This is the second time in this thread that this question came up as someone explained the way that they do it, but I hope that we can get some elaboration on what I have heard is a very critical measurement on these old color sets. I don't think that you are going to measure voltage, but I may be wrong. I think that it is a current measurement. With that being said, people using "amp clamp" meters could do this much differently than those using any other meter which must be connected in series with the circuit in question. Either way, a remote way of keeping an eye on this is highly beneficial.

Also, I have read that it is a good upgrade to install a fuse in this same circuit to avoid the evident damage that can be caused by something going wrong. So, if we can get specifics on the voltage or current measurement on which section (plate, cathode, grid), as well as some ideas on a good fuse size, I think that it would help a lot of the growing crowd of vintage color TV hobbyists.

I do have a rca wr-64a color bar/dot/crosshatch generator that I never used , I opened it for inspection and see a .005 dic exploded in the power section , I replaced it and its twin but the thermistor or whatever it is looks like part of it is missing so I'm not sure what the part number is and if it will work , I put it on a variac and there is oltage coming through but will let it sit overnight to help reform the electrolytics if they need to be , the one that is cardboard I should just replace anyway.
if it doesn't work I will have to use my cheaper b&k model 1230 digital i.c. color generator , it has purity , dots , crosshatch, gated rainbow and color level.

I looked on the schematic and HOT shows pin 3 and 6 at 200ma and pin 4 and 8 at 18ma 145v , pin 3 is the cathode as far as I know , so to measure the ma would be a pain without running a bunch of wires from under the chassis temporarily to measure it , but once measured if too high how do you get it down ?

In any RCA based color set it should SOP to measure HO tube cathode current(IIRC there should be a .47uF cap in parallel with the current meeter) and adjust the linearity coil for minimum cathode current. I prefer to follow the Sam's horizontal adjustment procedure, for a any given set, which usually has you adjust the horizontal oscillator for optimum performance prior to minimizing cathode current in the HO tube. It should be set to 180mA(IIRC) or lower if possible. Some roundys had a 250mA (ie. 1/4A) fuse in series with the cathode of the HO tube. IMHO it would not be a bad idea to add such a fuse mounted above the chassis...It would protect the fly from an horiz osc. failure, and allow for easy points to connect the meeter to for measuring the current.
RCA based HV systems have a tendency to blow out their flybacks from running too much current through the HO tube...Which is why replacements for RCA roundy flybacks are especially scarce compared to other flys.

You have a good flyback, Please don't waste it.

forgive me if what I'm about to say sounds stupid but I looked up the data on a 6DQ5 , it says the cathode is pins 3 and 6 , the schematic for the set shows pins 3 and 6 to ground and it says 200ma , so I am to measure between pin 3 or 6 to ground to get the ma ?

I break the connection to ground run it through the meter back to ground or I measure another way ?

or are we talking another pin not 3 or 6 ?

I only did ma once with a porthole and it was measuring one end and the other of a resistor and I got my ma reading and was able to reduce it by changing the value of the resistor, so on this color set to reduce it I touch the lin ?

don't put a resistor between ground and the pin to reduce?

I can tell you from the crosshatch that lin and width are adjusted so things are proper.

on the blue lateral I fixed that and I think I got the screen settings right , will have to go over it again to be sure.

mike

You might find a jumper to remove that connects 3 and 6 to ground. You break the cathode and then you measure the current there to ground. I have a ctc 10 and 11. All Horiz out cathodes usually go to ground

Wow, it lives. That set likely sat in that unheated garage for most of its life, so it saw extreme hot and cold along with humidity. It wasn't turned on for at least 25 years that I know of before you got it. According to my grandmother, that set might have been one of my grandfather's garbage picks.

so disconnect pin 3 and 6 from ground , hook the meter up and measure pin 3 and 6 to ground without it connected to ground ?

njroadfan he did install a fan , its a record player motor with a blade , he also noted several tubes replaced in 1972 and electrolytic replaced in 1979 that still works , just about every tube had to be replaced , the film caps and resistors held up , I replaced all but one electrolytic ( the one he put in ) to be safe .
I bet if he garbage picked it it was put out there because of the tubes it needed in 1972

mike

My grandfather was good about leaving notes with dates of install/repair on them. In this household we usually put the date of purchase on the manuals of electronics and appliances continuing his tradition. Thats mostly so we can curse more when it breaks well before it should.

too bad he or the previous owner removed the legs , you can see underneath where the metal thingies were screwed into the bottom for the legs to screw into
maybe if I can find legs and the screw thingies I can add them

ok had I read the entire sams I would have seen they explain how to do the cathode , they also mention how to do the hv regulator but I don't know if I want to mess around with that since I don't have a microammeter,
they do say adjust the hv control for 23kv at the anode , also they mention when doing the grey scale to turn the kine bias fully counterclockwise and then go on to the screen controls, they didn't say adjust so you get red to turn to yellow and yellow to white or grey , that is very helpful Electronic M , I thank you.

that 6BK4 sure has a blue glow inside it

mike

The "thingies" you refer to are leg mounting plates and can be found at most home improvement stores such as Lowes, Home Depot. You should buy plates that accommodate angled legs. The tapered legs can probably be found at the same type store or an unfinished furniture store. Some even have the brass caps on them. Not sure of the length of the legs on the Admiral. Someone on VK must have a CTC-12 type table model color set w/legs of this vintage and provide measurements.

-Steve D.

I may have a set of those angled leg plates. Probably some legs too.

Found them. The legs are 60's NOS made in Japan, my dad bough them by the case full when I was a little kid.

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