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  #31  
Old 11-02-2018, 10:04 AM
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Hold on, I think I need some clarification here.

I'm seeing the pin output for the Yoke on the schematic, but my confusion is arising from the fact that it lists a different resistance for the horizontal and vertical windings. How can I tell which winding set I'm measuring?

I'll double check, but from what I Pin 9 on the oscillator isn't used for anything. I looked underneath and it appears that it was soldered to the board for stability, but there are no traces on it, and no wires connected to it, so I'm fairly certain that in itself was not the cause of my yoke going bad.

As far as I can tell, the only wire that broke on the yoke is the lead going to the terminal strip on the side. I'll have to trace where that's supposed to solder and reconnect it, then do an ohms check to see if I'm okay. At least, that's what I'm figuring. I'm confused on your suggestion to dig out both ends, though. Can I not just reconnect that one blown lead and test from the pins on the socket? That will at least tell me if I've got worse problems before I start tearing into anything else.

That being said, is a yoke really supposed to be receiving enough voltage to spark like mine did? These were big sparks - think the size I'm supposed to be getting from my flyback, but from the yoke. If I were to pick up a replacement, or repair this one, what's to say something else wouldn't immediately blow it? Is there somewhere else I could be testing to check for that, or would a shorted yoke be enough to do what mine did?

I'm probably going to have more questions before I move forward. I'm a bit out of my element here, and I don't want to blow anything else.
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  #32  
Old 11-02-2018, 11:07 AM
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There's often several KV sized spikes on the h yoke winding... meanest shock I ever got was off one.
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  #33  
Old 11-02-2018, 11:56 AM
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Quote:
Originally Posted by Dubis7 View Post
I'm seeing the pin output for the Yoke on the schematic, but my confusion is arising from the fact that it lists a different resistance for the horizontal and vertical windings. How can I tell which winding set I'm measuring?

That being said, is a yoke really supposed to be receiving enough voltage to spark like mine did? These were big sparks - think the size I'm supposed to be getting from my flyback, but from the yoke.
If you trace the wiring on the schematic you see that the horizontal output circuit is connected to pin 4. The yoke coil connected to pin 4 ends at pin 8, so the horizontal coil is between pins 4 and 8, resistance should be about 33 ohms. That coil is also center tapped and connected to pin 5, so from pin 5 to either pin 4 or 8 you should measure 16-17 ohms. Likewise you can trace the vertical connections on the schematic to pins 1 and 2, and measure about 26 ohms. You don't have to just go by the diagram of the the yoke as a separate unit, you can use the rest of the schematic to give you clues. The sparks were a result of the current jumping a gap, it could be were the wire broke or because the voltage rose so high the current jumped to somewhere it should not have. Do remove any carbon tracks you find.
The way the horizontal output works is that the current passing through the flyback and yoke that scans the beam across the screen suddenly stops at the end of a line. The flyback and the yoke are inductors, when you stop the current through them suddenly they react by producing a voltage spike (several thousand volts) that tries to continue the current. This voltage spike is stepped up further by the flyback transformer to provide the anode CRT anode voltage. It also generates the boost voltage. The narrow spikes is why there has to be some capacitance to smooth them out to a level DC voltage after they are rectified. BTW, the ignition on a car engine use the same technique of cutting off the current through a coil to generate the spark.
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  #34  
Old 11-02-2018, 02:56 PM
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Alright, so I went ahead and ordered a spare yoke from Moyers. I'll have to pull this one apart and see if it's salvageable, but considering that I was already having High Voltage troubles, part of me is wondering if the origin of this whole thing - the horizontal issues, flickering on the screen, power draw issues, and now the lack of picture - isn't because the yoke was failing. Would that be possible?

Part of me wants to see about running additional voltage tests without utilizing the yoke, original or replacement, to protect myself from any further problems. If I were to jumper some resistors to mimic the picture tube filament and yoke resistances, would I be able to remove those from the circuit for the time being?
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  #35  
Old 11-02-2018, 03:03 PM
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The flyback depends in inductive resonance of the yoke to opperate correctly... you would need another yoke or a correct size inductor to have the fly work correctly.
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  #36  
Old 11-02-2018, 03:24 PM
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Understood.

Here's my issue, though. How can I tell if the yoke blew because of an existing short, or because of something wrong in the circuitry around it, without running another voltage test with the yoke hooked in? If it was something around the yoke, don't I risk blowing it again? Seems like a catch-22, unless I'm not understanding what to test next.
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  #37  
Old 11-02-2018, 04:09 PM
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Quote:
Originally Posted by Dubis7 View Post
Understood.

Here's my issue, though. How can I tell if the yoke blew because of an existing short, or because of something wrong in the circuitry around it, without running another voltage test with the yoke hooked in? If it was something around the yoke, don't I risk blowing it again? Seems like a catch-22, unless I'm not understanding what to test next.
I have NEVER seen a yoke in a tube set be blown by something.
The enemy here is heat & humditity plus high voltage spikes.
Put the new one in without worries........

73 Zeno
LFOD !
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  #38  
Old 11-07-2018, 09:07 PM
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Okay. Finally some good news. The yoke came in a few days ago, and I finally had a few minutes to sit down and swap it in. Sure enough, my picture is back! Everything seems to work appropriately now, though I haven't tried running a signal through it. I never had a problem with that before, but my next step is to hook up some sort of stable signal so I can adjust the yoke, those two magnetic rings on the collar, and the various controls along the back before I button it up.

So basically, here's what I think happened. Again, I'm no expert, so if this seems wrong please feel free to correct me.

I believe that the yoke began to fail a few months ago. Perhaps some of the material on the inside had begun to deteriorate, which caused the flickering and noise in the picture. I pulled it down to my workbench, opened it up, and got sidetracked for a few months. During that time, the yoke deteriorated further, or perhaps the improved startup from the new capacitors pushed it over the edge. Regardless, that was my culprit the whole time, and I should be good to go now that it's out of the picture, no pun intended.

By the way, does anyone have any recommendations for a good basic RF adapter? Tim sent me a test pattern DVD eons ago, but I can't use it since none of my DVD players have RF out. I picked up a Heathkit linearity pattern generator sometime back, so I suppose I could restore that to get a picture on the screen, but I'd honestly like to go ahead and just fire up something I already have ready to finish this up. Once I get that figured out I'm essentially minutes away from being able to put this set back into use.

Thanks again to everyone for your help. I couldn't have done this without you.
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  #39  
Old 11-07-2018, 10:01 PM
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Get a blonder tongue AM40 (AM60 or BAVMz if you want to transmit) those are among the best around though they often need a bit of work.

One thought if the dag is flaky and the yoke terminals are unprotected then flaking dag could have caused shorts and damage.
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  #40  
Old 11-08-2018, 07:02 AM
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The Dag on the CRT? It doesn't look flaky to me. It doesnt cover the whole CRT, but where it is, it's solid and has clear borders.

There is a lot of grime back there, not sure from what, not sure if I'll ever know. Maybe that caused some issues?

I actually already have a few blonder tongues. I have this dream of setting up multiple in-home broadcast stations. I need a manual, but if I understand correctly the company will still supply them if I provide the serial number. Ill try and tackle that today.

Speaking of which, I tried to use one of them a while back, and didnt get much luck. Just some red color. If I need to tear into mine, I'll post a new thread, but what sort of work usually needs to be done on them?
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  #41  
Old 11-08-2018, 07:36 AM
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Change the lytics in the power supply... that is usually all they need, but sometimes other lytics are bad and I think I've heard of one or two cases of a regulator or diode going bad in the PS.

You don't need a manual. Just mark the neg end of each cap on the board before removing it, replace one at a time, and make sure you have the right value replacement... that is how I did mine.

Test with output slightly above min and wired connection to set. If good move to antenna and do shango66 YouTube antenna making procedure for transmitter ant.
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  #42  
Old 11-08-2018, 08:15 PM
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Well, the geometry is done and the set is back together.

And yet, despite everything, I'm still seeing that flickering. I'm going to attach a video I took once I get to a computer to upload it correctly. If I were to describe it, imagine faint shadowy bars constantly flashing horizontally across the screen. It gets worse when I tap the set or walk by, and I'm seeing a narrow line moving up the screen, but that's not visible unless you're tracking it. Adjusting the vertical and horizontal doesn't seem to be impacting anything.

So, is this normal? Maybe I'm overreacting, but should I take a look at something else that could be causing this?
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  #43  
Old 11-09-2018, 10:12 AM
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Alright, sorry for the delay. Here's what I'm experiencing: https://www.youtube.com/watch?v=tM9k...ature=youtu.be. The interference is only visible on the video when I tap the side of the set, but it's always present, it just gets worse when the set is vibrated - walking near it will do the same thing.

I did notice that the rubber cup over the CRT anode lead wasn't sitting particularly flat against the CRT. I don't think the lead is lose, but could this be HV leaking from that lead?
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Last edited by Dubis7; 11-09-2018 at 10:14 AM. Reason: Adding more Information
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  #44  
Old 11-09-2018, 10:35 AM
WISCOJIM WISCOJIM is offline
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When you are hitting the TV it looks like dirty tube socket connections.

.
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  #45  
Old 11-09-2018, 12:22 PM
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Come to think of it, I didn't clean the tube sockets or tubes. That shouldn't be too hard. Would running a little sandpaper over the pins and spraying some contact cleaner into the sockets do the trick?
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