Nanao MS9 Horizontal Size not Filling Screen

[BlinG]

So I was helping my brother swap an MS8 for an MS9 chassis on his Astro City.

Was getting everything dialed in and the picture looks great, but I am having issues with the horizontal size not filling the screen. The pot on the remote board is turned all the way up and its about 80% filled. So I go to the Horizontal size limit pot on the chassis to fill it in, but as I turn it only the corners start to stretch. So basically it has a really bad pin cushion. So I think ok... I'll just adjust the SPC 15k pot, but it literally does nothing. When I adjust the Horizontal size limit back to its original state, the SPC pot works as it should with the pin cushion. I've tried the "Normal" and "Wide" jumper wire, but it doesn't make any difference.

I am kind of lost here with this and don't really know what else to try to fill the screen. Any suggestions?

 

[nem]

What's your B+ voltage?

I've never done this swap, but I've read that it's a common issue that the image won't fill up the screen without it curving at the top and bottom. But then others say it's fine?

There's also some resistor thing to bring back missing lines:

https://forum.arcadeotaku.com/viewtopic.php?p=279472#p279472

 

[BlinG]

I wasn't positive where to probe to measure the B+. It looks like it has never been adjusted though as there is still glue on the adjustment pot.

 

[nem]

You measure it from TP2. Easy enough to do with regular meter leads without killing yourself or creating short:

Red probe on red circle, black probe on black.

Voltage should be 76VDC for 15khz. If yours is over, adjust it to match and see if your issue gets better or worse.

 

[SF3BMX]

The MS9 works and looks great. Funny thing is that when we are playing CPS2 games, the horizontal size adjustment issue is still there but we can actually get away with it looking decent filling the screen near all the way. The bend on the sides almost isn't noticeable.

However when we pop in the CPS3, it's a whole different story. All 4 corners stretch out making the screen look tacky.

 

[lolo-san]

The issue the OP described looks very similar to the one in that video (it's in French) :

View: https://youtu.be/R8D1OeKULhA


In the video the problem comes from the original yoke of the MS8 which is not fully compatible with the MS9 chassis (the yoke swap fixed the issue at the end of the video).

 

[Psyko-M1]

The issue the OP described looks very similar to the one in that video (it's in French) :

View: https://youtu.be/R8D1OeKULhA


In the video the problem comes from the original yoke of the MS8 which is not fully compatible with the MS9 chassis (the yoke swap fixed the issue at the end of the video).

THANKS FOR THIS VIDEO.
You can use Close Captions and Auto Translate and it helps you understand.

 

[Anselmo]

What's the next move @SF3BMX ? Going to just get that MS8 Repaired or find an original MS9 yoke?

 

[SF3BMX]

What's the next move @SF3BMX ? Going to just get that MS8 Repaired or find an original MS9 yoke?

I don’t think so just yet. Gotta see what the b+ voltage is measuring first. If we can get the screen to fill like at least 90% with the current yoke, I’m calling it good. I still plan to get the MS8 repaired just to have a backup chassis handy.

 

[Hatsune Mike]

If the pincushion adjustment and width controls basically don't work replace Q508.

 

[Hatsune Mike]

Somehow I missed the original focus of the thread. On an MS8-29 yoke, the MS9-29 will never be as wide. The corners are the last thing to adjust because they have some headroom from the parabola applied using Q508; away from the corners, the width is already at its limit. You can cheat and raise B+ a bit for wider deflection at your own risk.

"Normal" and "Wide" jumpers are really S-cap selectors and are for correcting geometry when the image is set to a wide or narrow setting. It is a bit of a misnomer, though the more relaxed S-cap correction does result in a slightly wider raster.

This experience is the cost of people telling other people "it works great!" without noting caveats like this.

 

[SF3BMX]

So I finally have an update from the issue we had long ago with the horizontal not filling using an MS8 yoke with the MS9 chassis. We of course got a hold of a couple MS9 yokes and did the swap on the 1p cab with the MS9 chassis. Problem solved and I couldn’t be happier. Not only that, but the display looks 10 times better than what it did before.