New tube, trouble adjusting the image

dbstallman

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Well, I got a replacement tube for my big cab after the cargange detailed here : http://forums.arcade-museum.com/showthread.php?t=240883. Thank you jbacon1054!!

This tube is an EXACT match for my old one, a Toshiba LR27012. I have adjusted the flyback's focus and screen for a beautiful picture, but I now have some size issues. Here is the info on my chassis (including a low res scan of the manual) : http://wiki.arcadeotaku.com/w/Nanao_MS8-29

1. The horizontal with will adjust to see the entire screen for most of the first dozen boards I have tried, but only if the adjustment pot is turned all the way down. That means I basicly have no horizontal width adjustment any longer. There are a few boards (CPS-1 boards, Mr. Do so far) that have about 3 or 4 pixels beyond the edges on both sides and I cannot make it any smaller. I have moved the wire for the width to both W and N (it started on N) and games will only fit on N with the pot cranked all the way down.

2. There is rollover on the bottom of the screen. It isn't the tube since it moves to the other side when I swap the connectors for reversed/inverted display. I suspect this is a size issue as well since the vertical size pot is adjusted almost all the way up. When the pot is adjusted the other way, the vertical size is right at about half of the screen height, with no rollover.

There are some mentions of fixes on the Arcade Otaku wiki, notably one for rollover I am going to try.

The old tube didn't have these issues. Is this normal for a new tube when it is the same brand and model? Does anyone know of other adjustments on this chassis beyond what is listed in the manual? There doesn't appear to be a horizontal width coil on it. I haven't pulled the chassis back off yet, I was just checking to see if anyone had suggestions before I attacked it.

Thanks,
Brian.
 
Are you using the old yoke? If not did you check the ohms to see if both yokes read the same.
 
The new tube came with the yoke still on it.

I am using the old neckboard and chassis and I replaced the the yoke plug on the replacement tube since it was two separate plugs (mine was a single plug) and the one on the red/blue wires was seriously beat up. I left about 6" of wire from my old plug and cut the replacement tube's yoke wire at the plug. I wanted to give myself some more slack in the wiring. Could the extra length of wire be causing this issue?

Brian.

Edit : I'll meter the yokes this evening. What should I do if the values are different?
 
I've tested the ohms on both yokes :

Old yoke : Horizontal (Red/Blue) - 1.0 ohms
Vertical (Brown/Yellow) - 7.0 ohms

New yoke : Horizontal (Red/Blue) - 0.8 ohms
Vertical (Brown/Yellow) - 7.2 ohms

How do I get the new yoke to equal the same numbers? Are those numbers far enough off spec to cause the issues I am seeing?

Thanks,
Brian.
 
short answer. you can't without swapping the yoke.

that is really close anyway. other than ohm readings there is inductance which probably is the reason for the deflection difference. I would leave it alone or if you have too maybe you can swap out the width cap for another value to get more range. Many tubes I have swapped without swapping the yoke have the exact same problem.
 
Thats a bummer...

I was avoiding swaping the yoke because I was fearful of all the adjustments I would have to make to get it to bring up a nice bright and converged picture.... I guess I will save the yoke from the broken tube and deal with it for a while. If it bothers me too much then I will just go ahead and make the attempt at swapping the yoke.

The horizontal issue I could probably live with, since it wasn't noticeble to me at first and the few boards that it affects are right on the edge. The vertical compression with the rollover I noticed right away.

Thanks,
Brian.
 
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