CTC-10 adjustment lug?
 

I am finally back to this remote-contolled CTC-10W giant that has been pining away in my garage till I had room in the house to bring it in and work on it. The basic problem I have right now is no color - black and white is fine, and locks on the color signal, but once locks in all I get is varying intensities of purple in the picture instead of all colors. Tint control doesn't change it at all.
But first I have a question about this adjustment lug that's on the top side of the chassis in the color demod section, a grounded wire that can be plugged into two different positions. I can't seem to locate this thing on the schematics and want to make sure this is original, or not, and what it does, before I rule it out as possibly having an effect on the color section. Attached is a picture, lug is right in center of pic. Center lug = ground, two on either side are the adjustment plugs, two more on ends of lug go to wires and have a resistor bridged across them. thanks!

If the picture is just purple and you can vary the intensity of the purple by using the color control then the chroma signal channel is working but the 3.58 mhz oscillator is not. Check the grid of the 3.58 osc tube and make sure there is the appropriate amount of negative grid voltage. No voltlage means the oscillator is not running. One time I had a bad 3.58 crystal.

The tint control works by changing the phase of the locally generated 3.58 signal with respect to the phase of the transmitted signal so when the 3.58 osc is not working the tint control won't do anything.

Am not sure about the adjustment lug but it probably wouldn't have an effect on your problem. Track down what it connects to in the demod circuit.

I had gone thru it before and checked for opens on the coils just using an ohmeter in circuit and didn't find any opens. Also tried clipping another 3.58 crystal (a tube one from my CTC-5) with no change. So still poking around in it trying to figure out why I don't have any oscillating going on here. I may have to buy an oscilliscope to figure this one out. I will try checking the grid voltage with the voltmeter....Frenchy

I had this problem in a ctc-15 clone but it has been several years and I can't remember what the exact fix was. I know I replaced the crystal but it seems like there was an open coil in the osc. section. I think I salvaged one out of another ctc-15 clone chassis and that did the trick. Would probably be good to check all the voltages at the 3.58 osc tube.

I think I did use a scope to try and check out the 3.58 signal but it doesn't really seem like a necessity...the dc voltage readings should lead you to the trouble.

OK I just measured some pins on the 6gh8 oscillator tube:

pin 6 should be 222v, measured about 160
pin 3 should be 148v, measured about 100
pin 2 should be -5.8v, measuread less than -1 volt
pin 1 should be 54v, measure 60 (ok?)
pin 8 should be 2.2, measure 2.5 (ok?)
pin 9 should be 0.5 v, measure less than 1 volt (ok I think)

So the ones on the oscillator side of this tube seem off as opposed to the side that is in reactance circuit. This was measured with the existing crystal as I didn't see a change with a tube crystal clipped on top of it. The two 47k resistors on either side of the crystal measure correct ohms. Does this sound like maybe the 3.58 coil? Maybe measuring with an ohmeter was not sufficient. Someone had sugested this coil as a possibility before. I don't have any other problems with the set as per has good black and white, sound etc. Thanks!

Oh yeah and this tube checked good on my Heathkit tester and I think I even swapped it out with no change.

It's not a good idea to parallel the crystals in my opinion, just hook up the known good one and remove the old...it could have leakage that is loading down the circuit.

I'll try and look at the field service guide later today and see if I have any more suggestions.

cap replacement
 

any time you have a problem with an oscillator circuit in one of these oldies, it's best to go in and shotgun the circut with new caps, it takes a lot less time to do that than to try to figure out which one is leaky or off value.

I have only replaced the one 40mfd filter one, C729, in that area, as all the other caps look to be the hard brown type, not paper. Original or not, I don't know. Can anybody take a look at the schems and lemme know which ones would fall into the shotgun approach for this oscillator? There are about eight or so .01 caps around that tube, I suppose I could just start with those. First I will retest it with the new crystal/no old crystal, and recheck the osc. coil just to be sure I measured it right before. Thanks!

And one more thing, looks like that adjustment lug is on the schematics, it just changes between lugs on the vertical output transformer, but it doesn't say it's purpose. It's on one of the three output windings that feed right into the convergence board plug. The set already has vertical height, linearity and centering pots, so what is this extra tap for?

Here is the chroma section of the ctc-10:

http://www.retroaudiolab.com/sams/rcactc10.jpg

also it says about the jumper:

"Change jumper to ground bottom side of winding when more vert. tilt range is needed for optimum convergence".

Some more bench testing with the flyback fuse removed:
Clipped one leg of crystal - voltages did not change in osc. section.
In-circuit ohm readings on oscillator coil with set off:
D to A = .3 to .4
A to F = .5
B to C = 7.0
Between D/A and A/F windings = 10K range and rising (charging a cap somewhere)
There are a bunch of big disc-type caps in there instead of the usual mylar ones, they say "10,000 WV 244". Are these .01's? Can I replace them with regular 600v jobs or do I have to use 10,000 volt ones? Reason I ask is schematics etc. that I have don't list voltage values of the caps, so not sure. Don't know if I just don't have a copy of that part or it wasn't printed. Anybody have a listing of that for ctc-10? This would be for caps from about C700 to 730. Didn't look like a high voltage area so wondering why such big V caps used. Thanks!

<<<I'm also puzzled by the voltage values you gave for 6GH8 V20 and the values listed in the schematic Chad posted. You say that "pin 2 should be -5.8v" where the schematic Chad posted has pin 2 at -.5V. It's a problem.....>>

I just noticed that. My measurements actually sort of match up with the above schematics but the numbers on MY schematics are different (?!) I'm using schematics etc. that were sent to me by some nice person in here I can't remember who. On top it says "circuit diagram for ctc-10A, B, C........W. Mine is a 10W. So right now I'm confused also and not sure why my schematics match the chassis but the readings on it don't....Frenchy

My ctc10 schematic lists c701, c703, c710, c719, c725, c727, and c730 as .01 +100% -0% 500v. It doesn't mention what type of ctc10 it is (a, b, w, etc...)

John

I'm definitely looking at the right tube, labeled ctc-10...W chassis, the V703 a and b, 6gh8 marked as the 3.58 oscillator/reactance control. Pin 2 says -5.8v instead of -.5, pin 6 says 222v instead of 185, pin 3 says 148v instead of 110 etc., all pretty different that the ctc10 schems posted in the thread. Even the 250v feeding into both sides at the bottom say 275v on mine. I don't have a scanner working right now but I will try to see if I can get a pic of these schems posted, the printing on these looks more handwritten but don't see anywhere what company printed them. They include partial parts listing, tube layout, tuner adjustments etc. The part values seem to be the same on both, just the voltage readings look different. Anyway, the voltages I measured don't seem that far off from those other schematics (within 10%) so now wondering if they themselves still indicate a problem or not? Arghhh I got enough problems with no color, now I'm getting crosseyed with two schematics! Which ones right? : / Frenchy

Have you checked c718 the coupling cap for the reactance and 3.58 osc. section ? My field service guide showes pin 2 as -5.8 volts. Either Sams or RCA could be wrong, but the RCA guide shows -5.8 ( or thereabouts for all the chassis that use that tube config.

Looks to me like howard sams is probably wrong...I seem to remember -5 to -7 volts at that point on a ctc-15 clone and it is the same type of tube.

I think I'll just replace all the .01s in that area with 600 volt ones and then retest it and see if anything changes, sounds like a good bet, will report back after I do this. And a .1 that's there too, if that doesn't change anything, it's on to the 2 or 3 misc. caps that are left around that immediate circuit, big deal, will only cost me 10 bucks and give piece of mind anyway, and it's fun replacing caps (I'm sick I think). Thanks for all the input and numbers, fellow color roundie nuts!...Frenchy

I've replaced some caps but really don't see any change, color is still kicking in and has good b/w operation but color is just decoding as variations of pink (and green elsewhere if I totally overload the color control), and no tint control effect. Caps replaced were c126, c124, c727, c730, c725, c710, c703, c719, c707. On some channels the tint control DOES have a slight effect but just in the form of turning the color off at mid range and turning it back on at either end - it never changes any colors. So I know the tint control is good (also tested it with ohmmeter). I'm waiting for a 3.58 crystal just in case that ends up being the problem, till I swap that in I am not going to mess with it. And still have a leakage in the tuner tube which I am going to replace too but don't think it's causing this as b/w performance is great.
Should this oscillator be running regardless of anything else, i.e. should it be running all the time even if no color signal is being recieved or no antenna is attached? It should just be running if the set is powered up, period? Could something elsewhere in the color circuit be 'killing' the oscillator?
Good news - bypassing the thermistor in the power supply (which was further popping and crumbling away) really improved the set and the way it looks right now I dont' see why the set needs the pic tube booster on it. Was probably just a cheap fix for other problems (like this thermistor) with the set that the owner didn't want to pay for on an old set like this. This is what I suspected when the tube tested great on my tester too.

Check the color killer control, try adjusting it all the way to one side or the other...the color killer circuit may be disabling the oscillator.

Yo Chad, I think that did it, thanks! I clipped in my known good tube crystal again (one leg of existing crystal snipped open) and then turned the killer down and bingo now I have normal color operation! Killer control didn't help anything before the recap but where I had left it then was way too far on 'kill'. So it looks like it had been one of those caps I replaced but my lame killer setting was keeping me from finding out it fixed it. Guess now I can reconnect the original crystal just to actually find out if it is good or not to begin with too. Now on to the hard part - the remote control mechanism. Thanks! ...Frenchy

Anybody have any suggestions on the remote control chassis and hand unit? I put power to the clicker with a wall adapter and the button switches slightly spark so I know it's got juice but the relays on the remote chassis don't activate on any of the buttons. Tubes on remote chassis tested good, checked a few voltages and seem pretty good. Guess I don't know how to figure this out when I don't know if it's the chassis or the clicker that is not functioning, since I need both to be able to test either. Unless there is some other testing I can do on either alone that will tell me something. The one capacitor can on the chassis is cool and don't really see any paper type caps in there to replace. I assumed both were working at the time the remote control was disconnected by some repairman when a gear broke and made the remote unuseable for changing channels (it would have just spun the motor forever so he pulled some tubes out of it). Hmmm maybe I need to hook the remote to batteries instead in case there isn't enough amps in the adapter? I dunno...Frenchy

Try measuring the voltage from the wall adapter while no buttons pushed and then with a button pushed - this will tell you if you are drawing too much.

Adapter is 5.1 volts, none of the buttons make the voltage drop to less than 4.9 volts.

Doesn't sound like a problem with current draw. Do you have some info that 5 volts is the correct value? What batteries is it supposed to take?

I think many of these old remote transmitters used a mercury battery that was 4.5 volts. Usually there is a label in the battery compartment telling what type to use so you may try to verify what voltage was needed based on battery type. Also, double check the polarity you have hooked up from the wall adapter. As I remember, the mercury battery had the negative terminal at the small tip so it went in backwards from a regular alkaline or carbon zinc cell.

Try holding the remote transmitter right up to the microphone on the set and see if you get some action. Make sure the condensor microphone "phantom power" (270 volts I believe) is present at the mic. Check all of the DC voltages through the signal path beginning at the microphone.

It is supposed to take a 4.2V battery, this adapter is set to 4.5 volts, is actually putting out 5 volts. Another adapter I have says 4.5 volts but is putting out SIX volts so am not using it. I figured 5 volts would be no big deal instead of 4.2, no (?) I was going to worry about rigging up or finding a battery that would fit after I make sure it's working in the first place.
I'm going to go thru the chassis fully now and measure every voltage that is on the schematics, and will buy a scanner this weekend so I can post the schems here and maybe somebody can point me to potential bad caps to change. At the phono plug where the mic plugs into the chassis, the schems say should be 165 volts so I'll start there...Frenchy

I know I'm using the correct + and - connections on the adapter, and it is DC... attached is a scan of the schmatics for the remote chassis and the clicker...also here's a pic of the gear in the remote control mech I fixed. Glued the halves together with thin film of superglue, and now it should last forever with JBWeld and two washers to make it solid and take the place of the stress ring that normally goes on the stem. I might put little bead of JB along the other side's rim but can't put in in center as that's where the lock ring goes. I need this gear in there just to be able to change the channels since this set even changes the channel electrically from the console via a bar, not a channel knob.

One problem turned out to be a missing shield on the first 12ax7 tube, it's only one there that has a ground spring. At least I think it's missing. If I put a shield on it, the 'color up' control stops locking up. Might still be another problem and the shield is just masking it.
Two junky caps in the remote need to be changed too, that's next. The remote now works in spurts on three of the up functions, length changes if you slowly close the button switches so I betcha those caps have something to do with that (and the down buttons and channel button not doing anything.)

I'll take pics of it when I have it back together, it's very big with large speaker panel to the right, and great big 2-piece folding doors on each side that cover the whole front. Wider than a ctc-16 that I have that has speakers on both sides. Very deep too. This is one big darn set for not even being a combo.
Not sure they ever actually made that 14-button remote or if was just made for these publicity shots.
With pic tubes back then I can imagine film lights easily washing out most any color picture back then, let alone the glare off the curved screen and safety glass. Plus the problem of syncing the video with the film camera. Even if they just ripped the guts out and stuck a nice bright rear projection unit in the set it and no sync problems, it would probably still get washed out.

I changed the 50 mfd cap in the hand unit. Now instead of the color and tint working in spurts, they don't work at all BUT now the volume and channel work perfectly, no spurts. I have to get a .22 cap tommorrow and hope that is what is causing the color/tint problem, either that or I will try tweaking the screws on the hand unit and see if changes anything.