1960s Sweet 16 RCA television help

[Electronic M]

If the yoke is open or shorted it will greatly reduce the HV and throw off everything else in the horizontal section...Ever pull the H yoke leads on a CTC-15 and power it up?..I have.
Check your yoke like tolooz sayz. That magnet wire is coated in lacquer or some such translucent insulator and you'll need to scrape, melt, or dissolve it off before you can solder it...A short jumper if a section burned off will be fine...Just don't make it longer than it needs to be and don't place it where it could arc to other things.

It could be that pin 9 was being used as a terminal/tie point for other things in the horizontal osc or that it shorted to another pin...Sometimes if the osc is tuned close to the point where it screams adding a small bit of load to the circuit from a meter can push it over the edge in to the scream zone.

[ronl]

Looks like some carbon was created when the arc occured.make sure you scrape and or sand that black stuff off.its conductive.RonL

[zeno]

You have -20 volts on the G-1 of the output so the osc
is running. Testing around the osc will often throw it off
freq so that may be the scream you got.
If yoke wire broken you may be able to patch it if you can dig
out both ends. After that you are pretty much don to a bad
flyback, yoke or damper tube.

HINT ! When yokes get a shorted winding its usually on the
inside windings. Pull the yoke back off the bell. That will give
it air to burn better & you will see it often. Saves time !
If its not burning you may see on the CRT where it was burning.

73 Zeno
LFOD !

[Dubis7]

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.

[Notimetolooz]

Originally Posted by Dubis7

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.

[Dubis7]

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?