Nanao MS-2932-S Yoke

[mourix]

I got a Crazy taxi cabinet with an Nanao MS-2932-S monitor looking like this:


I measured the vertical yoke impedance of about 13 Ohms, so I am sure we're dealing with an open yoke winding here. Unfortunately I can't see any broken wires with the thing in place.

I read the yokes of this whole MS293X yokes are supposed to be the same inductance, but the current MS2933 yoke on ebay looks like this:


While mine looks more like this:


So that leaves me with the following questions:
Is the yoke something worth trying to unwind/rewind like those Indian youtube channels are doing?
And if not, would the different ms2933 yoke swap in directly?

Any thoughts?

[PrincessPrinPrin]

You have nothing to lose by trying to fix it unless you don't have the time. The advantage over swapping the yoke is that you don't have to do the purity and convergence procedures.

If you can find the point where the winding is open you won't have to unwind/rewind it, just join the parts together with a piece of wire. You can easily see which winding is open by desoldering the two pairs and check continuity across them. For instance in the pic below one winding is AB and the other is CD. Once you know which one is open you remove it and leave the other half of the toroid on the yoke. The point where the wire is open/corroded may well be on the side that can only be inspected when the semitoroid is off the yoke.

vyoke.JPG

[mourix]

Thank you! I will definitely poke at the thing.

In case it's unfixable, do you know if the MS-2933 yoke on ebay would work?

[PrincessPrinPrin]

I don't know. The horizontal coil might not be an exact match.

[mourix]

Yoke is off. Most stressful part was getting off the purity rings as they were completely glued to the neck from factory paint marker. Some sweat later and here we are:



So next up is disassembling the yoke and trying to see if I can find the issue. Let's see if I report back with great success or great failure

[nem]

Good luck.

I would try to look really hard for a break on the outside before pulling the thing apart.

[PrincessPrinPrin]

Not sure if I was clear enough but my suggestion was to leave the yoke on the tube to avoid the reconverging hassle. Anyway, the vertical tabs are the two without heat shrink.

[mourix]

I did not feel like I could get a proper view/workspot on the tube as it was. For now I did desolder the winding wires and the top one one does indeed measure in the megaohms.

I have looked a ton and can't find any break/corrosion from the outside. Now I need to get the toroid seperated from the holder. I guess I should try heat up the epoxy with a hair dryer?

[PrincessPrinPrin]

It's hot glue so it's softer but yeah some hot air will help for sure. I would use an L-shaped piece of metal as a hook to pull the upper part of the toroid off. Too bad there are those small boards in the way.

[mourix]

I got it off using a knife, small flat screwdriver and big flat screwdriver. Those Indian repairmen on TV really help.

There you have it, corroded right under the glue:


When putting it back, do you recommend hot glue or non acidic silicone glue?

[PrincessPrinPrin]

Hot glue but not too much.

[mourix]

Put on a wire:



Soldered it all back:



WOOHOOO



Now just to order some RTV silicone and I can call this one done. Thank you so much for all the advices, PrinPrin!

[PrincessPrinPrin]

Good job!

[nem]

Excellent!

[CTN]

Congrats

[geotrig]

well done ,nice fix, remembered reading the thread a few weeks ago so came back looking for it and didn't expect such quick progress !

[wonderbanana]

I dream of having this level of confidence and competence, nice one!

[MrSandman]

Congrats to fixing it. I say what wonderbanana says.
Again something new learned.

[mourix]

Thanks for all the really nice replies, guys

My RTV silicone came in this weekend, so I'll post an update on final convergence and adhesives when I’m done.

[Eddhorse]

Super work, you had nothing to lose which helps.
Luckily no unwinding , well played.