CTC-15 restoration
 

Starting a restore for a VK Member. This CTC-15 chassis is in rough shape. This is a high hours set and has signs of a lot of old and new work. It had a raster recently and CRT should be OK. I will be checking it.

There was no video however, then no nothin... there are some parts clipped, bad electrolytics and all but vaporized terminal strips under the square/ hots. some wires are not much better. A previous attempt by someone has a top-hat in place of a boost diode, glass diodes in place of the dual diode, resistors stacked to attain needed value, and a good number of those wooden looking :thmbsp: resistors checking way high.
Are there any pitfalls I should know about the 15 chassis? The things we were used to seeing 35 years ago don't necessarily relate to the state of that equipment 45 years later.
This may well be a diamond in the rough and I'm excited for the owner. Its even a remote. I'll post some pictures next visit.

Ground stakes on all boards

power resistors on chroma board with crystalized solder pads, reflow

jumper wires on top of chroma board,green corrosion, breaks off. The CRT will turn a solid color like screen control turned up too high.

Grid coupling cap, .01 between the power resistor and a 6GU7 will be weak, the other .01 grid coupling caps for the difference amps will prob be ok.

a trace on the side of the PCB near the horz out tube may fracture, back this up with a buss wire. It connects to a 390k resistor at the horz blanker tube. this shows as a loss of HV due to the blanker tube supplying too much neg bias to the horz out.

Caps in the vert feed back .0082 1kv mainly. the vert out cathode bypass cap, 50uf I think, its on the sweep board. Often ok, but if you doing for someone else then prob should be replaced.

1k power resistor on term strip near vert out trans, ofter the term strip solder has crystalized due to heat.

focus stick, sometimes goes bad mounted to side of fly.

horz output tube coupling cap. I replace this just to be safe.

Filter caps, of course these can be bad, if someone else set then I would restuff the cans just to be safe.

thermistor is fragile often broken.

on off switch is gets a lot of abuse. I use a remote power switch (the kind that are often sold during Christmas time for remote turn on of light) to save wear and tear on all my old vintage stuff.

Check line voltage. PT may have a high line voltage jumper that can be used. Better to use if line voltage is high, which is often the case.

check and adj horz eff coil, often a minor tweak can save 10-15ma or more good for fly life.

Check shunt tube and HV setting per sams. there is a 1k 5% resistor that is used to check voltage drop across for checking current in shunt. Generally you want to see about .5 to 1.5v drop across this while watching normal programing. think you will see this with the HV set to about 23kv and the fly current around 200ma

Thanks DaveWM

Good info, esp. the .01 coupling caps in the driver ckt. The .0082 in the vert is rated at 2KV. and is one of the cut components. This seems a bit over kill. I'm thinking 1600v replacement. Thoughts?
There is a thick layer of sticky dust on almost everything. A blower doesn't do much and Deoxit and Q-Tips is an expensive way to cleanup but the results are good. I really need to see everything. Do you have a recommendation?

yea 2kv I would stick with that, large pulse from the transformer.

I generally just used compressed air to get the big dust bunnies out of the way, use care around any coils or wires. If it really bothers you I have found rubbing alcohol and q tips works fine.

to check those chroma jumper wires just give them a slight tug, they will break instantly if bad, when they do break they stay put so it looks like they are fine.

there is prob a tube cap on the bottom, connected across the primary of the vert out, think its a .001 2kv and prob one on the audio out as well. May as well replace those, mainly since I cant test them at rated voltage (spikes).

Of course there is the across the line tube cap that should be replaced as well.

What I generally do is scan the parts list for HV caps, and make up an order from that, making sure I have them covered. I get them from mouser, HV caps are found in the film cap section as "snubber" caps.

Pictures attached.
 

The bright camera flash makes it look better than reality. The cleaned up spots do look better.
I think I'm going to inject a composite video signal and eliminate the tuner and IFs . The display is so bad I can't tell where to begin. I will say that the CRT cathodes are sky high so my dark screen issue will start in the video section. I have re flowed the grounds on the chroma board and that cleared up some filament issues.

futz around with the AGC pot. check the control grid voltage on the video out and see if it varies with the brightness setting.

try subbing in a new video out.

The flyback is the weakest point I would say.

Dave is dead on.

I would add color crystal.

If the crt is good try and lower the HV down to around 20kv, letting it run up to 25kv is just asking for the doughnut to arc out and burn up.

Being a shunt(load) regulator adjusting the HV down should add more current load to the HV rectifier and thus the fly-back. Output tube current is the operative here and if any thing would reduce fly-back current it would be the CRT brightness, screen grid volts at the HOTube and the circuit being at resonance. A screen grid method was used in later chassis designs in the square screen, tube, portables.
I have checked the AGC pot and it slightly lightens the dim raster, but not the answer yet. I'm going to check basic voltages at the Vid out and work back.
The CRT had intermittent green as the loose cap was touched. I re-flowed the green pins and then re-flowed them again with an added thin solid wire inserted in the socket pins and is now stable. The CRT checks really good otherwise but Im not comfortable with this turn of events especially when I could see someone previously soldered the pins before me, but its stable for now.
Forward boys, we march on.

Where would I find a schematic (RCA / PDF or such) with scope readings or more voltage details? I found a basic that I've been using but it's very basic at www.boxcarcabin.com/rcaschematics.html, but I need more info.
Right about now I wish I had a test jig and a million dollars:lmao:

Those are a bunch of scans of the schematics that came with the tvs I posted there.

You would think shunting the fly would cause more heat and it may, but keep in mind the failure mode of the flybacks. Its arcing from the top of the doughnut to the bottom and its caused by high voltage breakdown. I have disassembled and re waxed and repaired a few of these. Trust me when I say shunt it.
If you want to lower overall heat, use the high line voltage tap on the power transformer. That will lower the headroom on the high voltage and increase the life of everything in the set big time.

Ill look and see if I have the full service manual on the 15.

PM me your email and what info you need (what areas you are having issues with). Ill get you a custom set together tonight.

I have tons of information on color stuff and cant scan it all with this crappy little scanner.

Still dark
 

I'm thinking its a blanking issue. CRT checks VERY good. I have focus voltage, screens are up, but not much brightness. The bias sw has little to no affect even in the service mode.
My Sams shows there should be +90 v on the blanker grid, but there is not. The plate has 130 plus or minus. On the very left inch or less of the screen I can see noise, the rest is black.
What develops this +90 volts?

confused, you have HV correct?

what are the pin voltages on the CRT again?

whats the plate voltage of the 12BY7?

Plate 12BY7 210

CRT K 284 G1 147 G2 903 well into cutoff right?

hmmm

plate voltage is off, should be around 320v as should be the K G1 should be around 200v. You have about a 130v neg bias vers about 120v. which is not much. don't think that would cut it off.

I would check the brigtness control and make sure its working properly. as you need to get a handle on the odd plate voltage. Make sure you are reading with no signal. I like to use a VTVM for testing voltages, although a DMM would be fine, just not a VOM.

Pin 2 of the blanker should be -95v.

Make sure you have about 5kv of focus voltage. If the focus voltage is too the CRT will be dark.

I would say some resistance checks of the video out tube would be a good start, need to that plate voltage up (even though that would cut it off even harder, but start there.

Oh are are you reading the red K of the CRT? should be +320, just in case you read one of the other K and did not have the drive G1 drive fully advanced.

check the plate of the AGC keyer tube, look for the 600v PP spike on a scope.

The chassis is out of the cabinet in stand-alone. The HV is of course reduced (no DY attached) as is the pulse from the purple wire winding so the AGC plate pulse is low for now but still at 300 V peak and the blanker is low at the grid at -34volts. There are a number of resistors that have been replaced by me due to out of tolerance by a moderate amount. Plate resistors on the GU7s are out as well and still need replacement. Should be 27k and presently measure 21 / 22K and the tubes run hot. Focus volts is in the ballpark. Still the only video to be seen is at the left 1 inch or so of the screen and that's not very bright considering the screen volts and a good CRT with HV. Still plugging away.

I had a set that did a similar thing. If I turned the contrast one direction it looked like this(see thread: http://www.videokarma.org/showthread.php?t=252862) but id I turned it the other way, I got a weak but full raster. ALL the canned electrolytics were dry. Good HV and B+, screen volts OK.

The quad E-can at the end has been replaced (bad seal, dripped, dried out) others are OK. I have subbed to make sure any way. Replaced the .1 on the agc line to the IF strip and the video from the detector looks more stable on the scope. Looks good going into the 12BY7, bad coming out I may just shotgun all the related components and reflow all the joints. I hate black magic fixes like that, I would prefer to know what exactly the fault is, but this is getting time consuming for this one problem alone and I have not yet seen what other things will have to be addressed.

screen resistor/contrast pot/service switch for trouble with the Video out.

I have also replaced the grid coupling cap on the video, but if you are good at the grid then that should not be a problem, unless is just a bit leaky. That "could" account for the low plate voltage. I know you did voltage checks but don't remember the results.

I am assuming the 50uf cap on the contrast control is not shorted.

Gonna go Oh Yea when ya hear this one.
 

Brief raster on the left dark screen with close focus. Drum roll please


The focus rectifier! Likely shorted. After seeing decent signal on the scope (after soldering all the parts in the area and grounds I still had the strange symptom yet wave forms and DC on the CRT grids and cathode looked good. The last thing to ponder "the focus grid. The voltage was a bit rich in AC content so a rectifier change was in order. I also discovered the previous person had a 100 ohm resistor in place of the 1 meg in series with the focus lead also.

I now have a picture in near focus but a unresponsive focus control. I can now view a picture and see there is much to do like AGC and sync issues. Vertical gain next, then color. The CRT is looking decent but the cap is scary loose and I've had to re-flow the solder in some of the pins.

Any suggestions to secure the base to keep it from moving short of JB weld? I don't want wires to break from movement

Progress is being made

if there is still some of the brown glue left but just not stuck, I have had luck with a product called "flex zap" you can get it at model shops. Its a kind of CA glue but has some give to it so as not to shock break in heat cycles.

If the focus is not responding, 1st check the focus voltage and make sure you are getting an adjustment of at least 500v. I use a simpson 260 in the 5kv mode.

does the focus coil look cooked?

Focus coil looks OK. I am going to check the value of the HV cap between the coil and the stick. I have run across a number of creative part subs so far.

As far as the CRT base cap goes I want secure it against mechanical movement but would like to have the option of getting behind it in the future if a last ditch (desperate) effort is needed by somebody. My concern is that even slight movement over a long period of time will lead to wires breaking off at the nibs. Present servicing and restoration just adds to the problem as the chassis is reconnected for testing and repair at present.

I think the flex zap will fill the bill. Never tried to break the bond after using it, but I suspect it would not take a lot.

when you were having the dark CRT before, I thought you said you had checked the focus voltage?

I have not seen a bad 130pf but that does not mean much as I have not been doing this long. Did you get a chance to see if the focus voltage varies at all with the coil? If not I would think one of the coils may be open. the way I understand how it works is sorta like an adjustable bucking transformer, two coils out of phase, the core simply moves from the out of phase to the in phase thereby adding or subtracting to the pulse from the fly that is then rectified by the stick. the 66meg is a load and the cap a filter.

I used an old meter and it showed just over 5kv but I suspect what it didnt show was the high AC content. Moving forward.

Pogress, but small vertical sweep.
 

Finally have a watchable picture but still a ways to go. My latest focus problem was a 100k resistor across the focus coil cooked its way down to 1700 ohms! I also found missing resistors in the horizontal osc stage. The most pressing issue for now is the vertical sweep. All vertical caps have been replaced except the cathode electrolytic. The tube has been swapped with no improvement. A couple out of tolerance resistors replaced as well. Can someone tell me what the deal is with the VDR? They never went bad in the old days but time could create a new scenario after 45years. The controls work, just not enough vertical gain.

I did find a bonding agent for the CRT base called Loctite GO2 from home depot. It seems to grab onto anything and when cured it has the feel of silicone with very little flex. It cures clear. The package indicates it should take the heat...Time will tell. The CRT was showing signs of being intermittent so I re-flowed all the pins secured the base after seeing stability return. The emission is good on all guns

This restore has not been fun at all due to the previous attempt to fix it. There have been poor choices in part substitution, values changed in an attempt to "make it work". Added to that this set shows signs of very high hours manifested as heat damage to terminal strips, heat blasted wire, and this chassis wins the Most Number of Out of Tolerance Resistors award of any restore or repair I have done.

End of rant:scratch2:

1st thing to confirm is that electro, if its open the vert will deflection will suffer.

next are you testing it with the convergence board plugged in?

I would not worry about the VDR, but if everthing else check out you can remove it and test. I use a cap tester to apply a voltage to it, and check the current thru it. IIRC its about 1ma at 800v. I doubt its a problem unless its shorted.

also check the boost voltage and look for some high value resistors that supply the boost voltage to on of the pots (I cant recall if RCA calls it the height or lin pot, but one of them will have boost voltage on one side and B+ on the other).

I think there its a 2.2 meg or some other high value resistor that if it drifts up will hurt deflection.

I got zapped but good once by a vertical centering pot on one of my many RCA sets. I think it had B+ on it.

you said all the vertical caps, if that does not include the boost filter cap, check that as well. Its a .1 or .22 can't recall, mounted on the sweep board. This is if the other stuff does not help. there is also a resistor in the grid circuit of the vert multivibrator that is pretty critical, 24k I think, look for the gold band 5%.

I'll look for those two parts in particular. The cathode cap is on the change list for sure. I'll also be checking for about a 150 ohm path between convergence pins 1 and 2. I'm going to verify the B Boost voltage but I suspect it's close as the screen for each gun is pretty perky.

Parts changed

Pictures added

Still suffering a lack of vertical deflection.

I now have a remote unit but I believe its for another RCA set but I think it could work. A freq counter loosely coupled shows 35 to 50 khz depending which button is pressed. That seems a bit broad to me and there is only one adjustment. I was expecting there to be only 1.5 kc apart for each function.

Lets talk REMOTE...control that is
 

This set has a CPT10-A reciever and the handheld does not match the Sams schematic. The diagram shows a different component layout and has trimmer-caps to tweak each function.

The handheld I have has only one adjustment and the measured freqs dont match up even close to several functions. Some do. The only ID on the inside on the PCB indicates E-143365-1 RCA-5.

The only trimmer was soldered so it was replaced. The channel freq is right on and I'm back to the original issue. I get the idea this is not the remote for this chassis or I'm going to have to play capacitor roulette for each function.

Is this the wrong one? Is there a practical solution.

Did you change the lytic on the sweep board? I think it's 50uf... can't tell in your photo if that's a new sprague or and old one in the cardboard sleeve. That capacitor usually opens up the picture if adjustments do not.

Other than your picture not opening all the way, it looks really nice. I'm jealous that your Vislanda is a remote set. Mine is not.

That (cathode) cap has been replaced and checked and subd.
At this point all parts have been replaced with the exception of the yoke and V. transformer. The path through the convergence is good at about 130 ohms. I have not replaced the VDR. B- boost checks about 1100 volts with a triplet meter.

Wish I could say this ones mine. It belongs to a local VK collector, I'm helping him out with the varied technical issues.

This one (CTC-15) is a beast as far as this vertical issue goes. This is a high hours set and had a number of problems you'd expect to sometimes find, but all at the same time. It also has had a lot of previous attempted repairs.

Odd thing is I recently had a CTC-16 that fought for Vertical as well. It just barely makes it and I'm taking a wait and see, figuring if it gets worse, it'll be easier to find.

Hard to tell if it's a linearity problem or height problem, can you post a pic with crosshatch pattern? If it's not lin, is the correct voltage reaching the vert out tube plate? If not, I'd replace the vert out trans or sub a yoke to see if either of those solves the problem.

This is the best I can get at the moment. The top tends to crush. I can get linearity with a smaller sweep but if I go for max the bottom streches and the top flatens out. I don.t think the DY is bad as there is not a whacked geometry. The VOTrans is quiet and cool. With the service switch on there is about 396 volts on the plate of the output tube section, Grid 0v and cathode 85v. so its pulling current and the plate volts seem healthy. I suppose there could be a shorted turn but I would expect a more visual symptom.

Now since the last chassis removal the brightness control has stopped working. Wish I had a jig and more room. argh...

Does the vertical centering pot work? I has 2 go bad in my 2 16's and cause strange problems. Might just be a broken wire on the brightness pot. my 9 has extreme hours on it and all the wires want to just fall off when you look at them wrong. Looks great otherwise. :)

I can see a white ceramic tubular capacitor under the deflection board. Don't know what it's for, but I bet it needs to be replaced. Those are never good.

mstaton, In case you didn't know, this is the same set that was posted under Curbside months back ago, which you posted.. I found a shipper on U-ship to Florida..

http://www.videokarma.org/showthread.php?t=254480

I'm surprised it's still listed on Ebay.. I guess it hasn't been the three month mark yet..


The vertical is starting to look better and better.. Hopefully the Remote issues can be worked out..

I found other threads on here who have had the same issues with this and the 16 chassis.. seems to be common

http://www.videokarma.org/showthread...ighlight=ctc16

http://www.videokarma.org/showthread.php?t=147493