View Full Version : Testing a CTC-11 horizontal hold control


Kamakiri
11-21-2016, 10:40 AM
Have an issue with hot plating on the horizontal output tube of a CTC-11, and I'm pretty sure that I've traced it to a bad horizontal hold control.

This is described as a sine wave coil. I assume to test it properly the set has to be set up on a scope, but is there any way to test it for an open while out of circuit?

old_tv_nut
11-21-2016, 11:06 AM
Have an issue with hot plating on the horizontal output tube of a CTC-11, and I'm pretty sure that I've traced it to a bad horizontal hold control.

This is described as a sine wave coil. I assume to test it properly the set has to be set up on a scope, but is there any way to test it for an open while out of circuit?

Not really familiar with the chassis, but looking at the SAMS, to ADJUST it properly requires a scope and adjusting the H osc simultaneously to keep sync.

Out of the circuit, you can check for open with an ohmmeter, but if the problem is a shorted turn instead, that would be hard to tell.

It looks to me like it's the only DC path to the H osc plate. If that is correct, and it's open, the H osc would die completely. Is that what you are seeing with hot-plating? It also means you could check for an open while in-circuit (with power off, of course [adding this comment in case someone less knowledgeable reads this in future]).

Electronic M
11-21-2016, 11:10 AM
Have an issue with hot plating on the horizontal output tube of a CTC-11, and I'm pretty sure that I've traced it to a bad horizontal hold control.

This is described as a sine wave coil. I assume to test it properly the set has to be set up on a scope, but is there any way to test it for an open while out of circuit?

Sure. If your schematic lists a resistance for the coil you can check that is in that ball park with the set off.

It may be possible that the adjustments are far enough off that it may not be oscillating.

BTW you should not need to have the output tube plugged in while testing the horizontal oscillator circuit with the set on. All the output does for the osc. is provide a feedback that the phase /AFC system uses to pull the frequency/phase of the osc. into lock, so without that feedback it should free run (which some sam's H adjustment procedures have you force it to do anyway).

Kamakiri
11-21-2016, 11:18 AM
Right....the reason that it's hot plating is that I'm missing the -60V on the 6DQ5. Caps have been replaced and I'm halfway through checking the resistors but I'm really thinking that it's the horizontal hold control. Low hours set that's been moved a LOT in its life.

old_coot88
11-21-2016, 12:34 PM
With the 6DQ5 removed*, check for plate voltage (pin 6) of the H osc tube. If it's missing, trace back component-by-component toward the 380V source.

*Even with the plate cap disconnected, the 6DQ5's screen grid (G2) will get cooked when there's no drive on G1 (the drive signal is what develops the negative bias voltage on G1).

Kamakiri
11-21-2016, 01:11 PM
Only thing I'm missing is the -60V (the RCA manual says -57...close enough) on pins 1 and 5. I have zero.

old_coot88
11-21-2016, 01:49 PM
Just to confirm.. you do have 240V on the plate (pin 6) of the 6CG7, right?

Kamakiri
11-21-2016, 02:03 PM
Not sure. Since I've had the chassis on the bench I've just worked off tube resistances. I'll check it tonight and report back.

holmesuser01
11-21-2016, 06:34 PM
Have you verified that the ground stakes are good? These sets are known to break the solder between the PCB and the stake pins on the chassis.

Kamakiri
11-22-2016, 07:46 AM
First thing I did was check all the grounds :)

Kamakiri
11-22-2016, 07:48 AM
Just to confirm.. you do have 240V on the plate (pin 6) of the 6CG7, right?

I'm not used to working with chassis out of the cabinet. Is this something that I can do with the 6DQ5 pulled and the chassis on the bench, or should I just jig it back up in the cabinet?

Electronic M
11-22-2016, 09:18 AM
I'm not used to working with chassis out of the cabinet. Is this something that I can do with the 6DQ5 pulled and the chassis on the bench, or should I just jig it back up in the cabinet?

You should be able to bench it (assuming if there is a yoke plug B+ interlock that it does not break osc. B+).....B+ voltage may be off a bit with it out of the cabinet, but then again having the H. output not working correctly will affect the B+ anyway (and is the main factor in changing the B+ out of cabinet on a working chassis) so it should not matter...

DavGoodlin
11-22-2016, 04:13 PM
Only thing I'm missing is the -60V (the RCA manual says -57...close enough) on pins 1 and 5. I have zero.

As I understand it, the -60 is developed when a sawtooth of sufficient p-p amplitude hits the 6DQ5 grid. This is called contact bias. If the oscillator is way off frequency, the amplitude of the sawtooth drops sufficiently to make the grid LESS negative. Low bias will cause HOT to conduct and plate to glow in the center, no bias lights up the plate as you are experiencing, both kill HV. If not using an oscilloscope, use the peak-peak scale on a VTVM set to AC.

Go from the hold control coil (either terminal) all the way through the wave-shaping network of caps and resistors to pin 1 of the 6DQ5, which is not plugged in for this test.
If 270 volts P-P is not found at the hold coil, the oscillator is not running. If something close is found, see where it gets stopped or attenuated.

old_coot88
11-22-2016, 04:30 PM
OK one more time.:) Yes/no, is there plate voltage on pin 6 of the 6CG7? Sams calls for 240V. Is it, or any fraction of it, present on pin 6?

Kamakiri
11-24-2016, 06:37 AM
With the variac at about 80V and the 6DQ5 pulled, I was showing ~270

Kamakiri
11-29-2016, 11:48 AM
If 270 volts P-P is not found at the hold coil, the oscillator is not running. If something close is found, see where it gets stopped or attenuated.

I've got the 270 at the hold coil. There's only so many parts left here that it could be :headscrat

Electronic M
11-29-2016, 12:32 PM
I've got the 270 at the hold coil. There's only so many parts left here that it could be :headscrat

Is that 270 AC like the post you quoted is looking for? If so try to follow it with a scope towards the output grid.

old_coot88
11-29-2016, 05:37 PM
To tell if it's AC or not, put a cap (any random value .001 - .01 mf) for DC isolation in series with the test lead, and put the meter on AC.

Kamakiri
11-30-2016, 06:12 AM
The 270 was DC.....measured with my meter on the hold coil.

Now, here's something interesting. DavGoodlin was kind enough to show me how to get the sawtooth on my scope, got nothing. But it was also the first time I'd tested it under full line voltage....I'd been running it on a variac at about 85V. Just me being cautious.

Since I got nothing, I went back to test the voltage at the same point on the horizontal hold coil with the set plugged in at full line voltage. It started out at about 280 VDC, and over the course of 30 seconds dropped off and ended up leveling off at 65 VDC. :headscrat . No AC voltage shown.

I didn't have time before work this morning to re-check pin 6 of the 6CG7, but I will later.

miniman82
11-30-2016, 08:31 AM
Sagging there indicates the second plate on your 6CG7 is being dragged down, in other words the tube is being turned on hard which lowers plate voltage. You have no waveform, the oscillator is not running. I would expect grid voltage on the same triode section to be high, confirming the stuck 'on' diagnosis. You need to have a close look at the components around that tube; drifted resistors, leaking caps, bad grounds, the works. Synchroguide circuits are fiendishly simple, which paradoxically makes them difficult to troubleshoot at times because there is so little to go wrong.

old_coot88
11-30-2016, 10:57 AM
Have you verified with an ohmmeter check that L32 (the H.osc plate coil) has continuity to all three legs? there should be 25 ohms between pins 1 and 3, and 5.5 ohms between pins 2 and 3.

The 25 ohm section is good apparently, since you're getting full B+ to the plate of the 6CG7. But if the 5.5 ohm section were open, it would kill the oscillator completely.

Kamakiri
11-30-2016, 11:56 AM
The 25 ohm I've got. The other sections I've got 48 and 60 ohm, not 5.5......

old_coot88
11-30-2016, 12:46 PM
On blowing up the schematic for a closer look, that 5.5 is actually 55 ohm. My mistake.:( At least the coil has continuity.

Kamakiri
11-30-2016, 01:38 PM
Roger that, thanks :)

On to the resistors....

DavGoodlin
11-30-2016, 04:18 PM
Roger that, thanks :)

On to the resistors....

Hope that is closer to the trouble since you replaced the caps. Try varying the coils just to see if its off so far it quit.

Kamakiri
12-01-2016, 07:08 AM
Made it about 3/4 of the way through the resistors....so far so good. Board grounds are fine.

Part of what makes this repair difficult for me is that I have to set aside a lot of the methodology I use to fix early b/w sets. It's been my experience with color sets that trying to component test at random just doesn't work the way it does with early black and white, which is what I'm used to.

For example, if you have a vertical sync problem with an early b/w, just start testing and replacing resistors in that whole section, because chances are that even if none are wildly off, most of them will *be* off by enough that it will destabilize the whole circuit. So far I haven't found a single resistor that's made it out of its 10% tolerance.

Kamakiri
12-01-2016, 07:12 AM
Try varying the coils just to see if its off so far it quit.

How?

That's kind of what I'm thinking is going on....that over time techs have used the "golden screwdriver" technique to compensate for weak components, and now I've got something that's fresh and totally out of whack.

Nick was spot on in his earlier post. There's not a lot that *can* go wrong here, which constantly leaves me thinking I'm barking up the wrong tree.

DavGoodlin
12-01-2016, 11:32 AM
These RCA's can be undone by stupid stuff, most heat-related. I just got done with a CTC16 where a wire run on top of PW700 next to a 6GU7 tube socket pin, was arcing only under full AC power and smoking the cathode resistor. Visually, the resistor was the prime suspect until seeing the little flashing arc under the socket. The resulting potpourri of reeked of classic RCA fly arcing and made the set's owner think his NEW flyback just burned up.

So all looks well on that oscillator PW, even the tube and socket? Its just not normal for an synchroguide oscillator to NOT run. The coils could not have been adjusted out so far as to shut it down I suppose.

Maybe Im grabbing at straws here but see what is external to the circuit, causing issues DC voltages are coming *TO* the stakes. on the osc PWB. Start with resistance at D, to see if maybe a shorted AFC diode (which are over on the vert PWB) should be very high like 780 K ohm.

H-275 vdc, A -386 vdc, F-6.3 vac, D - zero dc and 40v p-p ac, G and E both close to 260 vdc. If any cap gets leaky like C604, C605 and C606 its curtains.

If I was not out of VK memory, Id post the schematic for clarity.

Electronic M
12-01-2016, 01:00 PM
If I was not out of VK memory, Id post the schematic for clarity.

Perhaps it is time to get a free image hosting account on a site like Flickr or Photobucket.

How are the traces? I've seen open and or crappy traces on that era of board...If they look bad or voltages are not getting places I tend to reflow/add new solder to the traces.

kvflyer
12-01-2016, 01:56 PM
FYI, I have a Photobucket account. It is now rubbish, full of delays, popups, begging for money etc. Many times I just cannot even use it.

Just sayn' (but I guess I get what I am payn' for...)

DavGoodlin
12-01-2016, 02:26 PM
FYI, I have a Photobucket account. It is now rubbish, full of delays, popups, begging for money etc. Many times I just cannot even use it.

Just sayn' (but I guess I get what I am payn' for...)

My flickr account is bit flaky - I log on several different PC's. At work it acts one way, at home another, the laptop still another, and on the phone its very hard to deal with.

Flickr its great for posting numerous pictures of a restore and makes sense when you have lots of photos, instead of one-off posts like this, where it is kludgy to use.

Electronic M
12-01-2016, 02:46 PM
Flickr acts the same on all my devices....VK's upload/image size limits prevent me from uploading %99.8 percent of the pictures I have, and a hosting site has proved easier for me to implement/use than resizing my images and hosting them on VK.



FYI, I have a Photobucket account. It is now rubbish, full of delays, popups, begging for money etc. Many times I just cannot even use it.

Just sayn' (but I guess I get what I am payn' for...)
It is a bit less clunky if you run adblock plus in your browser (I still get popups occasionally). My photobucket account is effectively dead to me....Once I (rapidly) ran out of storage capacity and they started prompting me to buy more, I switched to flickr and have not looked back....Well I do occasionally go there to post an old photo still on the bucket.

Findm-Keepm
12-01-2016, 09:14 PM
Call me late to the party, but Dad's (incomplete) Sams for the CTC11 is marked up pretty good. There's this (not in Dad's handwriting) - HOT cherries, check Osc tube filament for 6V. Was half. No corrective action listed.

And plenty about contrast, swapping guns to check CRT, and other non-germane stuff.

PF Reporter also had an instance...

http://www.americanradiohistory.com/hd2/IDX-Service-&-Sales-IDX/Archive-PF-IDX/IDX/60s/PF-Reporter-1964-04-OCR-Page-0024.pdf#search=%226dq5%22

Me, no experience earlier than a CTC12, so no real help beyond that note..

old_coot88
12-01-2016, 09:39 PM
Gotta wonder at this point if either of the windings might have shorted turn(s), dragging down the Q enough to keep the oscillator from starting.

miniman82
12-02-2016, 05:29 PM
All the horizontal circuits were mostly the same, even a 16 is easy to troubleshoot with a CTC-9 schematic if you know what to look for.

Kamakiri
12-03-2016, 03:24 PM
Ed stopped by. I think we nailed it. He said that the horizontal diodes are leaky. Since they're mounted on the vertical board, I didn't even think of it.....but I had a feeling that it was a garbage in/garbage out situation.

He said to replace them with germanium diodes. Any suggestions?

Electronic M
12-03-2016, 08:26 PM
I've seen standard 1N4007s work fine as horizontal AFC diodes...I'd try those first if you've got em.

old_coot88
12-03-2016, 08:53 PM
Just curious :), while the AFC dual diode can definitely cause loss of H sync, how would it being 'leaky' prevent the osc from running?

Not tryin' to be a smart arse, just thinking it could be a fault condition I never ran into before.

Tom9589
12-04-2016, 08:30 AM
The actual AFC diodes are selenium according to SAMS. I don't know what the effect would be if you used a different type of diode. Most notably would be the forward junction voltage: germanium - 0.3V; silicon - 0.7V; selenium - 0.95V. I suspect that leaky AFC diodes might cause the first stage of the 6CG7 to drive the oscillator way off frequency to the point of shutting down the oscillator.

Of all the AFC diodes I replaced, the only problem I observed was lousy AFC operation, never an oscillator shutdown.

Kamakiri
12-04-2016, 09:03 AM
Just curious :), while the AFC dual diode can definitely cause loss of H sync, how would it being 'leaky' prevent the osc from running?

Not tryin' to be a smart arse, just thinking it could be a fault condition I never ran into before.

Not sure. You're totally correct in what you're saying, because my experience is the same. We were triaging this and my 5....he had the 11 chassis on the bench.

Honestly not quite sure, but it's a direction to go in.

I spied this on ebay, so I said what the heck, let's do this instead:

http://www.ebay.com/itm/262744695681?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Kamakiri
01-09-2017, 09:07 AM
Well, obviously that wasn't it.....but here's where I'm at now.

Traced the issue to PW600. I have both the +275V and the +386V voltages, but I still have no -57V. Board's been recapped. I replaced two of the resistors to no avail.

I still have a couple yet to check, but since those are values that I don't stock, I figure I might as well order the disc caps as well just to cover all bases. What voltage should I get? Or, should I even bother with the discs?

Ed and I worked on this chassis for at least a couple hours weekend before last. We're both scratching our heads.....

DavGoodlin
01-09-2017, 09:45 AM
Ok this is going out on a limb, but tube sockets have been failing* while looking otherwise intact on recent repairs:scratch2:try the 6CG7 socket, it may have a conductive dust path underneath. Trace those hold coil wires too. I don't have Sams 550 but the resistance table for all the 6CG7 pins needs to be checked.

*Both CTC16 color demodulator 6GU7 sockets and a 12BY7 in the second set could not be helped with deoxit or new tubes.

old_tv_nut
01-09-2017, 12:16 PM
Do you have the 24 v and 260v on the plates of V601? This would show if the tube is drawing current.
Since the -57v is developed by rectification of the horizontal drive pulse, I imagine its absence only means there are no H drive pulses.

Do you have an oscilloscope? A quick check around V601 would show if the oscillator is running at all.

Kamakiri
01-09-2017, 01:19 PM
Working backwards in my mind from over a week ago (been a rough week with my wife coming home from rehab), I remember that the oscillator isn't running at all. We checked and re-checked board traces, tube pin continuity, and grounds.

As I understand it, the +275V and the +386V voltages show that everything going into the board is fine. Once again I'm stymied because there are only so many parts here....

Kamakiri
01-09-2017, 01:20 PM
Ok this is going out on a limb, but tube sockets have been failing* while looking otherwise intact on recent repairs:scratch2:try the 6CG7 socket, it may have a conductive dust path underneath. Trace those hold coil wires too. I don't have Sams 550 but the resistance table for all the 6CG7 pins needs to be checked.

*Both CTC16 color demodulator 6GU7 sockets and a 12BY7 in the second set could not be helped with deoxit or new tubes.

Conductive dust path. Hm. That'd be a new one, but it would also make perfect sense.

old_tv_nut
01-09-2017, 01:24 PM
Working backwards in my mind from over a week ago (been a rough week with my wife coming home from rehab), I remember that the oscillator isn't running at all. We checked and re-checked board traces, tube pin continuity, and grounds.

As I understand it, the +275V and the +386V voltages show that everything going into the board is fine. Once again I'm stymied because there are only so many parts here....

In that case, I agree with the hints about sockets. If the plate voltages on the socket are way high (the same as the supplies), it could indicate either that the plate pins aren't connecting (no tube current) or the filament voltage is low (also no tube current). Can you see the filament light up?

Kamakiri
01-09-2017, 02:16 PM
Yep, filament is definitely lighting. Tube socket aside for a moment, do you think it would be a waste of time to shotgun the rest of the components on that board?

old_tv_nut
01-09-2017, 03:13 PM
Yep, filament is definitely lighting. Tube socket aside for a moment, do you think it would be a waste of time to shotgun the rest of the components on that board?

I would measure the voltages on the socket pins first.
[Edit: can you get at the bottom easily? Otherwise, a socket extender can be helpful if you have one.]

retrogear
01-09-2017, 04:14 PM
Give us all the voltages on pins of 6CG7 hor osc and afc. You can remove 6DQ5 hor out and the damper tube to measure it

Kamakiri
01-09-2017, 08:12 PM
Thanks....give me a day or two and I'll get it back up on the bench. I have to repair my socket extender.....one of the long metal rods pulled right out of the sucker last time I used it :mad:

I've been running all of the tests with the 6DQ5 out. To do the diagnosis last time, I had the yoke and convergence board out of the set and plugged into the chassis and everything laid out on the bench so that I could move it around more easily.

teevee
01-09-2017, 09:45 PM
Jack Darr did a good writeup about servicing the Synchroguide circuit, if I can find that .pdf I'll post a link..

DavGoodlin
01-10-2017, 12:40 PM
Jack Darr did a good writeup about servicing the Synchroguide circuit, if I can find that .pdf I'll post a link..

Thanks, that would be great to review as we retreat inside and jump into the weeds on these chassis.

I have 3+ more older RCA's waiting after finishing two CTC16s where tube sockets looked normal but were definitely bad..

Kamakiri
01-10-2017, 03:46 PM
Tested resistances. Everything is perfectly in line, except pins 8 and 9. Measured from M1, I get about 8K. Measured from chassis ground, it jumps around (assuming because I'm not using a VTVM) in the range of 40-120 ohms. Should be zero ohms on both.

Since both pins are ground, are we looking at a bad tube socket?

DavGoodlin
01-10-2017, 04:03 PM
OK, now jumper to ground pins 8-9 on your test socket and see what it reads, better yet, apply power. Not sure what M1 -is I'm' using the RCA schemo.

old_tv_nut
01-10-2017, 05:03 PM
Tested resistances. Everything is perfectly in line, except pins 8 and 9. Measured from M1, I get about 8K. Measured from chassis ground, it jumps around (assuming because I'm not using a VTVM) in the range of 40-120 ohms. Should be zero ohms on both.

Since both pins are ground, are we looking at a bad tube socket?

Not sure what M1 is. The pins and the ground trace on the circuit board should all measure zero ohms to chassis ground. VTVM or VOM will not make a difference - a ground pin or PC board trace should be a very low resistance short to chassis ground.

One more thought - make sure your ohmmeter reads a solid zero when you short the leads together.

Electronic M
01-10-2017, 06:00 PM
Sam's for the 11 can be found here: http://earlytelevision.org/pdf/rca_ctc11_sams_550_2.pdf

I don't see a M1 on it, but then again I did not take much time to carefully look...

If socket pins, that are shown on the schematic as grounded, measure over an ohm to chassis, then either the ground path is bad, your meter has a problem, or the connection points are dirty. Suspect board to chassis ground connections, traces, and socket in that order.

Findm-Keepm
01-10-2017, 07:37 PM
Why M1 (B+ rectifier)? Most resistance readings are taken from Chassis ground - using M1 as a reference for any DC or Ohms measurement will result in odd values - those doubler caps charge and discharge, giving odd values. Clip the negative lead to chassis, and measure to the pins....

Lower left of Page two on the Sams gives the instructions - common negative (Chassis)....

Have you verified the resistances of the ground traces on the board to the chassis - measure the trace, not at the corner eyelets. Those eyelets are 90% of the problems with most RCAs. IIRC, you resoldered those early in the thread.

Kamakiri
01-10-2017, 07:39 PM
It's also where many of the resistance tests for that tube are taken from.

Findm-Keepm
01-10-2017, 07:52 PM
Pin 8 and 9 to ground should measure close to zero - and you have resistance. Taken from Socket (above) or pins (below), they should both be close to zero.......I'd start there. Runs to the eyelets....simple trace. Assuming the solder connection is good - bigger the blob, better the job does not apply here - go for a clean, shiny fillet.

Kamakiri
01-11-2017, 08:17 AM
Cleaned the snot out of the socket and ran my iron over the pins just for good measure. We're now down to 1 ohm, confirmed with both the Snap On meter I always use, and my Jackson Tele-Volter that I rebuilt.

Time to try this again.....

Kamakiri
01-11-2017, 01:10 PM
Okay, same result. I think it's time to go looking elsewhere and go back further.

Tested voltages at V11, the horizontal oscillator (6CG7). Looking for a -.8v on pin 2. Fired the set up, and had that -.8V, but as it warmed up over 20 seconds or so, it decreased to zero and went to a positive .8V. The next thing back in the chain that I would normally go after would be the AFC diode, but I already replaced that.

Now I'm clueless.

Electronic M
01-11-2017, 01:49 PM
I'd suspect leakage in C72 ,73 and C75 dragging the grid positive.

I've been known to manually bias (with an external PS) grids to see if that is the cause and not the symptom...

One thing my Silvertone CTC-15 clone taught me is just because something in the H system worked before things went wrong, don't mean that it did not choose to die in sync with the initial problem...That set had raster and a hint of video (but bad lytics) to start, and after a recap it was dead...Change in the H osc paper cap put it far enough out of freq. range that it shorted the damper tube (which is surprisingly vulnerable to that in that set) and boost diode.

Kamakiri
01-11-2017, 01:53 PM
I'd suspect leakage in C72 ,73 and C75 dragging the grid positive.

What operating voltage would you suggest as replacements?

dtvmcdonald
01-11-2017, 02:53 PM
A couple of volts off at the Horiz Osc grid is OK ... look at the scope trace,
its 30V P-P.

That circuit is hopeless to diagnose if its not working close to properly.

Make two tests: first look at test point 60 on a scope ... is it right?

Second ... WITH THE SET OFF feed the biggest voltage square wave at 16 kHZ
your generator can muster into the plate cap of the horizontal output tube.
Scope point 61 (aka 101). You should get something ringy looking there,
problems with the horizontal output transformer or convergence
board could cause problems, especially a short on the convergence board.
(You should try the thing with and without that plugged in).

I had a fault in that circuit on my CT-100 that was fixed only
by shotgunning all, and I mean all, non-coil parts. And it was still
working ... scoping did not help.

I would shotgun everything except coils.

Electronic M
01-11-2017, 03:28 PM
What operating voltage would you suggest as replacements?

Looking at the B+ voltages and drop I'd go 450V at least...C75 should probably be 500V or more.

Doug makes a good point...I've heard of resistors internally going open or shorted under working voltage and testing fine under lower meter voltage...If you have spares this is a very reasonable place/circumstance to shot gun.

Kamakiri
01-11-2017, 03:31 PM
Just on the oscillator board, or how far do I go?

I've never seen a resistor do that, but it would make perfect sense if it's a condition that could reasonably occur.

dtvmcdonald
01-11-2017, 10:15 PM
A resistor most certainly did exactly that after warmup, on my CT-100,
in exactly that circuit. I never got it to do it outside the circuit
(testing with DC) after I removed them. I never knew which one it was.

Perhaps it the high voltage pulses.

Kamakiri
02-14-2017, 11:15 AM
Welp, the set's fixed!

After rebuilding almost everything in the whole set, I asked my buddy Ed to give it a whirl. He couldn't find ANYthing wrong with it. He re-checked the horizontal hold control and the sine coils, and both were fine, but he tried subbing them anyway. Horizontal hold control, nothing. Sine coil, bingo. That did it. The sucker tested fine but was the problem in the end. He jigged it up in an 11 he has at his house, and it's got a beautiful picture and everything locks in solidly.

Man, some of these things will drive you to drink....but I sure did learn a lot in the process :)

old_tv_nut
02-14-2017, 11:25 AM
Hi, could you explain what tested fine on the sine coil? Was it the resistance that was OK? For example, I don't think a shorted turn would necessarily test bad for overall resistance.

Kamakiri
02-14-2017, 11:26 AM
Exactly....the resistance read correctly.

old_tv_nut
02-14-2017, 11:37 AM
Thanks - good to know to still be suspicious when the resistance checks OK.

DaveWM
02-14-2017, 02:58 PM
odd, I wonder if the sine coil was not making good contact at the pcb? generally you can short those out and the will still work ok, in fact IIRC shorting and unshorting while adjusting them is a way of setting them up.

Kamakiri
02-14-2017, 03:27 PM
I reworked every solder joint in the whole PW600 section, that was one of the things that I did early on, then redid. All I know is at this point, I have a CTC-11 with one hell of a lot of new parts :)

This set originally came from Dave A. Here's a shot of it when I first picked it up at Dave Goodling's in Lancaster PA back on Feb 20 last year.....

DavGoodlin
02-15-2017, 02:29 PM
This set originally came from Dave A. Here's a shot of it when I first picked it up at Dave Goodling's in Lancaster PA back on Feb 20 last year.....

Great job Tim. I agree that coil issue was perplexing, since shorting that coil is S.O.P. on CTC12 and later chassis to center the hold control range. Not so on the CTC11, this coil is center-tapped - an auto-transformer to feedback from plate to the osc grid, so you don't short it because of how critical this loop is. The adjustment is in the Sams 550-2, page 16 and requires a scope to match amplitude of the two peaks.

I would not mind putting that coil on two of my ring-testers to see if that fails the coil against a good one from my working '11, the resistance measurements sure didnt:sigh:

Is that CRT a 21FJP22, or has it a formed safety glass for the 21FBP22? I covered it up and did not peek so I wasn't tempted to keep it:D

DaveWM
02-16-2017, 09:45 AM
Great job Tim. I agree that coil issue was perplexing, since shorting that coil is S.O.P. on CTC12 and later chassis to center the hold control range. Not so on the CTC11, this coil is center-tapped - an auto-transformer to feedback from plate to the osc grid, so you don't short it because of how critical this loop is. The adjustment is in the Sams 550-2, page 16 and requires a scope to match amplitude of the two peaks.

I would not mind putting that coil on two of my ring-testers to see if that fails the coil against a good one from my working '11, the resistance measurements sure didnt:sigh:

Is that CRT a 21FJP22, or has it a formed safety glass for the 21FBP22? I covered it up and did not peek so I wasn't tempted to keep it:D

is it the sine coil or the horz freq coil that was the issue. the labled sine coil does not have a center tap. Which one is the horz hold anyway, from the attached schematic there is a sine coil (no tap) labled horz hold and then there is the taped "horz freq" labled coil. IIRC the tapped one is the horz hold control mounted for user access and the sine is not, just mounted on the pcb.


hmm looked at again, I just must be mis rembering, sure looks like the sine labled coil is off pcb and is indeed the horz hold control.
Just checked the manual, I see there were changes in how those coils were used.

Kamakiri
02-16-2017, 10:20 AM
Frequency coil, I had been meaning to come back to this thread and correct my statement when I realized that I called it by the wrong name....

Kamakiri
02-16-2017, 10:23 AM
Great job Tim. I agree that coil issue was perplexing, since shorting that coil is S.O.P. on CTC12 and later chassis to center the hold control range. Not so on the CTC11, this coil is center-tapped - an auto-transformer to feedback from plate to the osc grid, so you don't short it because of how critical this loop is. The adjustment is in the Sams 550-2, page 16 and requires a scope to match amplitude of the two peaks.

I would not mind putting that coil on two of my ring-testers to see if that fails the coil against a good one from my working '11, the resistance measurements sure didnt:sigh:

Is that CRT a 21FJP22, or has it a formed safety glass for the 21FBP22? I covered it up and did not peek so I wasn't tempted to keep it:D

I saved the coil for ya, I'll send it to you next time I have to send ya something ;)

It's an amazingly cataract free FJP.....and an RCA Hi-Lite to boot :)