Anyone ever successfully repair a blown yoke?

modessitt

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I'm seriously considering making the attempt as I can't find a replacement anywhere...
 
K5515. I've been trying to track one down for a few weeks with no luck.

The yoke in question has a burn mark on top with about 8 strands broken. No vertical reading. I've been thinking about unwinding it, figuring out where the broken strands reconnect, and seeing if I can get a proper reading again. Thoughts?
 
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I've been thinking about unwinding it, figuring out where the broken strands reconnect, and seeing if I can get a proper reading again. Thoughts?

It's worth a shot if it's already broken. ;)
Since you can already see the few broken strands, then it may only be a few turns in before all the broken spots are found. It might not even make much of an impedance difference if you just unwound the broken section and reconnected right there where the good begins if you can get a decent reading there. (given that the coating on the rest of the wiring looks good)
 
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Yeah, I've thought about doing readings from each side of the yoke to the different strands to see which is connected and seeing what the readings are. I don't know how close it needs to be to original. This is a med-res yoke, and I've already learned from experience that another yoke with the same ohm-reading will NOT work as a replacement.

I don't suppose there is a way to measure impedance with a DMM?
 
This is a med-res yoke, and I've already learned from experience that another yoke with the same ohm-reading will NOT work as a replacement.

So you know what the original ohm readings are then?
Wonder how close it is to something like a K4915?

I don't suppose there is a way to measure impedance with a DMM?

Not unless the meter has a specific setting for impedance that I am aware of.
I go by resistance, as that's all my meters will do.
 
So you know what the original readings are then?
Wonder how close it is to something like a K4915?

From measurements sent to me, the impedance for the 5515 is the same as for the 4915. It's just that the physical size of the yoke is bigger for the 25" tube. I have a 4915 yoke here, but I'm pretty sure I can't pop it onto a 25" tube and hook up a 25" chassis and get a good picture. As the yoke (and the monitor it is attached to) don't belong to me, I don't want to risk blowing it up, too....
 
Have you googled the numbers off of the label on the yoke? I've found that Wells-Gardner used lots of Samsung yokes. Some are still available from Samsung (SEMCO).
 
Have you googled the numbers off of the label on the yoke? I've found that Wells-Gardner used lots of Samsung yokes. Some are still available from Samsung (SEMCO).

No, I haven't.

The numbers on this yoke are as follows:

9A2870-001
DOK-8638T
 
Okay, I've been measuring from the terminals to the broken points, and I have found two strands - one connecting to each side. From one strand to a terminal, I get about 3-4 ohms. From the other strand to the other terminal, I get about 39-40 ohms. Now, the vertical yoke is normally about 44 ohms, so I'm thinking if I connect these two strands, I should have a complete yoke again, albeit with a few less windings than original.

Now, how to connect the strands? I guess I can file the ends a bit to remove any coating, then solder them together? Do I need to heat-shrink it or anything to keep from accidentally touching it during a yoke adjustment? Could I take a short length of insulated wire and use that to connect them (hard to get in there), or would the voltage through the yoke burn off the insulation?

I'm going to connect this somehow and then hook it up this weekend to see what happens, so anything that can help is appreciated. I know that if I can get this yoke repaired and working, the owner will be VERY happy....
 
Okay, I've been measuring from the terminals to the broken points, and I have found two strands - one connecting to each side. From one strand to a terminal, I get about 3-4 ohms. From the other strand to the other terminal, I get about 39-40 ohms. Now, the vertical yoke is normally about 44 ohms, so I'm thinking if I connect these two strands, I should have a complete yoke again, albeit with a few less windings than original.

Now, how to connect the strands? I guess I can file the ends a bit to remove any coating, then solder them together? Do I need to heat-shrink it or anything to keep from accidentally touching it during a yoke adjustment? Could I take a short length of insulated wire and use that to connect them (hard to get in there), or would the voltage through the yoke burn off the insulation?

I'm going to connect this somehow and then hook it up this weekend to see what happens, so anything that can help is appreciated. I know that if I can get this yoke repaired and working, the owner will be VERY happy....

all of your assumptions are correct - I add that the resistance is not that citical. A few extra or a few less windings will make no difference. Over the years I have repaired many yokes with burnt wires caused by the rubber wedges going 'gooey' and frizzling the wires. I have had about a 50% success ate. Good luck.
 
all of your assumptions are correct - I add that the resistance is not that citical. A few extra or a few less windings will make no difference. Over the years I have repaired many yokes with burnt wires caused by the rubber wedges going 'gooey' and frizzling the wires. I have had about a 50% success ate. Good luck.

Thanks. any insight on connecting the strands?
 
yoke

I repaired a 27 inch tv(with a ceiling mount)i picked up once that had a weird verticle deflection problem. Turned out that a winding had busted and i had to pull back two inches to reconnect and it looks great. had to solder and then i heat shrink it just to be careful.
 
There used to be an enamel coating that was created for the TV industry.... I haven't seen it in years though.

You need something heat resistant that can be 'painted on' or some tiny heat shrink tubing.

Do you have a flyback ringer? If so, you can use that to check for shorted windings in the yoke. Also, if you have an LCR bridge you can use that to measure the impedance of the yoke which, as you discovered, is a measurement that is quite a bit different than raw resistance.
 
I do have a ring tester, so I can check from each lug to the respective strand to make sure it is good to that point...
 
There used to be an enamel coating that was created for the TV industry.... I haven't seen it in years though.
You need something heat resistant that can be 'painted on' or some tiny heat shrink tubing.

I wonder if you could use something like a decent two part epoxy and coat it with that?
 
I have nothing useful to ad but I just want to say that I can't wait to hear how this turns out. I love these threads where people try to fix something that most people would give up on. Good luck!
 
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