Testing a Yoke: Eico 944
Testing my first yoke coil : Stancor DY-1 . My EICO 944 yoke tester instructions says in order to test it correctly, the shunt resistors across the coils have to be removed first. I haven't pulled the yoke yet, but are they the resistors in the yoke that have to be removed? Has anyone ever done this before? It tested bad when I did the vertical coils which have the shunt resistors across the coils.
Any advise would be appreciated. Also, if it tests bad, anyone know where I can get a tested Stancor DY-1 for an Emerson 571? |
There are usually resistors under the back cap of the yoke.
Honestly, unless I've recapped a set and it has deflection failure/serious defects I never bother to test the yoke...They don't fail that often, aren't too hard to find replacements for, and often if a designated sub is NLA one from a similar junker set will do. |
Thanks for the advise. There was arcing snaps coming from the yoke vicinity and about a 1/2 second video drop out when it happened. The ballast tube recently blew after a snap and I'm trying to back engineer the culprit.
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If you are getting intermittent insulation breakdown on the windings, the 944 isn't going to pick it up.
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Most sets run enough current/power through ballasts (which if not a sealed glass cased type tend to rust open) that if the ballast opens while the set is on then the point where it opens will arc/snap.
I agree with polar. Also if the aquadag coating gets close too the yoke it can arc to it in two circumstances: 1.) dag grounding failure (this is bad, quickly fix it if it is broke), 2.) Dag grounded, but too close to the yoke and yoke is arcing to it...This can be due to unnaturally high yoke voltage, or normal yoke voltage and insufficient insulation between things. Some sets normally have a snap or 10 immediately after power up/power down...Snaps, after it has had a raster for 30+ sec, are where you should be concerned, and snaps that are extremely loud. |
Thanks for the grounding failure information. I have a second set. I'll swap out the yoke and check the aquadag coating and ground issue.
Is there something I can spay or coat the aquadag near the yoke to prevent arcing? |
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Sorry for bumping in here but I had never noticed that posted before. Thanks |
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Electronic M: the aquadag around the picture tube ground loops off the yoke mount has chipped off. That is probably the issue of arcing around the yoke ... so thanks!
Would anyone know what I can paint or apply on the glass area around the missing aquadag to complete the ground? Or is it best to just more the loop? |
A product called 'slip plate' works (there are other products too). To apply it remove CRT from TV, mask off places the dag should not be, feel for loose patches of the original dag and knock loose patches off, spray new coating on over glass and solid parts of original dag making a reasonably thick complete coating, allow to partially dry (to where it won't run), remove masking, allow to finish drying.
Assuming the dag has not formed islands you can temporarily ground the dag by placing a spring or wire against a good part of the dag and connecting that wire to ground. If the dag is not connected to ground somewhere then the outer dag can float to several thousand volts potential relative to the chassis...Once it floats high enough it will arc to ground at anyplace where it can....If you ground it somewhere decent it will be at ground potential and not arc......Now if there are dag islands all of them need to be grounded or they will arc to each other and or chassis (thus why you don't want islands: too much of a pain to ground multiple things). |
just good the product and applied it. Will let you know if the arcing stopped. There was no aquadag under the grounding loops. Thanks.
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