Help With Yoke Adjustment on a KV-27FS100

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Tempest_2084
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Help With Yoke Adjustment on a KV-27FS100

Post by Tempest_2084 »

I've decided to dig out my KV-27FS100 to see if I can fix the geometry and convergence issues it's having. As you can see from these pics (240p Suite on the SNES) there are several issues that need to be fixed. The geometry is 'ok' but could be better (the infamous yoke sag is obvious), the convergence on the top and bottom areas is pretty bad (most noticeable on the monoscope pattern), and there's a horizontal linearity issue going on on the left hand side of the screen (the squares get smaller on that side, it's easier to see on the convergence grid pattern).

The only way to fix these issues is with a yoke adjustment, as I've done what I can with the service menu. I actually did this a few years back (it was way worse before) and found it to be quite a difficult chore. Any tips on how to make this easier? I really don't want to lose what I already have and make things worse. Can I loosen the screw only a little and make tiny adjustments or will that risk cracking the neck tube?

Sorry for the washed out pictures, it's hard to take a good screenshot with a modern phone in a dim basement. Other than the convergence issues the colors are actually very vivid and not washed out looking.
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Tempest_2084
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Re: Help With Yoke Adjustment on a KV-27FS100

Post by Tempest_2084 »

Ok I've been told that I really shouldn't do a full on yoke adjustment as the geometry is already pretty good (I think it could be better, but better safe than sorry). What someone did recommend is that I loose the yoke clamp every so slightly and try to pull the yoke a little closer. This might fix both my linearity issue and my convergence issues (might being the key word there) and if I keep the wedges in the yoke shouldn't move too much so I shouldn't mess up the geometry and can try and walk it back if things go sideways. My only fear with this is that I don't want to beak the neck accidentally by trying to move things with the clamp too tight, but I also don't want to loosen the clamp too much so the yoke drops or moves if I don't support it

Someone also suggested playing with those dials on top of the yoke board. I have absolutely no idea what those dials do (something with dynamic convergence) and they don't seem to be documented anywhere. Has anyone tried these before? I do have some convergence strips and magnets to play with, but you'll notice that the convergence issue is more or less along the top and bottom half of the screen, not in a corner so I'm not sure how well those would work.
Taiyaki
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Re: Help With Yoke Adjustment on a KV-27FS100

Post by Taiyaki »

Pretty sure that at 27 inch you're not going to get that any better. That's actually one of the best looking FS100 sets I've ever seen in terms of geometry, and I always believe in opening these up to tweak them as much as possible. You already went beyond what ~99% of users would do.

Geometry and convergence on these sets is always about compromise. Looking at your photos I'd say you sacrificed some convergence for geometry at the bottom right. You would be able to improve the convergence with permalloy strips but you'll worsen the geometry. With time there will be minor changes too (sometimes potentially making things better as weird as it may sound). So you really can only go so far. Geometry and convergence issues are always going to be a part of the CRT experience even with mid range and smaller sets.
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Tempest_2084
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Re: Help With Yoke Adjustment on a KV-27FS100

Post by Tempest_2084 »

Taiyaki wrote:Pretty sure that at 27 inch you're not going to get that any better. That's actually one of the best looking FS100 sets I've ever seen in terms of geometry, and I always believe in opening these up to tweak them as much as possible. You already went beyond what ~99% of users would do.

Geometry and convergence on these sets is always about compromise. Looking at your photos I'd say you sacrificed some convergence for geometry at the bottom right. You would be able to improve the convergence with permalloy strips but you'll worsen the geometry. With time there will be minor changes too (sometimes potentially making things better as weird as it may sound). So you really can only go so far. Geometry and convergence issues are always going to be a part of the CRT experience even with mid range and smaller sets.
Thanks for the advice, I guess I didn't realize that the geometry is about as good as it's going to get. I guess what I'd like to try and do is fix the convergence a bit if I can, so maybe I'll try playing with the strips first and see what I can do. The horizontal linearity issue is something I'd like to fix too but oddly enough it doesn't really show up in games (at least not that I've seen). Do you think it's worth trying to push the yoke in a little to fix the linearity issue? Do you think that might also help the convergence a bit?
Taiyaki
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Joined: Fri Apr 04, 2014 11:31 pm

Re: Help With Yoke Adjustment on a KV-27FS100

Post by Taiyaki »

Tempest_2084 wrote:
Taiyaki wrote:Pretty sure that at 27 inch you're not going to get that any better. That's actually one of the best looking FS100 sets I've ever seen in terms of geometry, and I always believe in opening these up to tweak them as much as possible. You already went beyond what ~99% of users would do.

Geometry and convergence on these sets is always about compromise. Looking at your photos I'd say you sacrificed some convergence for geometry at the bottom right. You would be able to improve the convergence with permalloy strips but you'll worsen the geometry. With time there will be minor changes too (sometimes potentially making things better as weird as it may sound). So you really can only go so far. Geometry and convergence issues are always going to be a part of the CRT experience even with mid range and smaller sets.
Thanks for the advice, I guess I didn't realize that the geometry is about as good as it's going to get. I guess what I'd like to try and do is fix the convergence a bit if I can, so maybe I'll try playing with the strips first and see what I can do. The horizontal linearity issue is something I'd like to fix too but oddly enough it doesn't really show up in games (at least not that I've seen). Do you think it's worth trying to push the yoke in a little to fix the linearity issue? Do you think that might also help the convergence a bit?
You can try, but I think you'll find it will feel like playing with a rigged Rubik cube.

It's worth trying with the permalloy strips though. Although it's not usually recommended, you can try stacking a couple right next to each other too. Sometimes I've found this work. Find a sweet spot where you're happy with the balance between geometry and convergence. I generally favor geometry, but in your case the convergence in the lower right might warrant a slight recheck. If you can't fix it though, I'd still say that's a really nice set.
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