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Author Topic: 27" Betson won't sync -- advice needed  (Read 708 times)

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jarrett

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27" Betson won't sync -- advice needed
« on: July 31, 2012, 05:08:11 pm »
I've got an old ArcadeVGA card hooked to a 27" Betson multi-sync (44-4070-RT).

Everything works fine in VGA modes -- 640x480 and 800x600 look great as always. However, if I run MAME in any low frequency mode, the monitor doesn't want to sync up anymore. The entire picture is combed and distorted and drawn half off the display.

Hoping the ArcadeVGA card had worn out, I ordered a replacement. It didn't help.

What do I do now?

MonMotha

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Re: 27" Betson won't sync -- advice needed
« Reply #1 on: July 31, 2012, 06:02:21 pm »
Ultimarc has a "tri sync utility" that you may need.  This monitor has DDC, so it will try to tell the PC what to do.  Unfortunately, it just usually ends up confusing the drivers in the process.

If that doesn't help, this monitor's sync separator seems picky.  Try using separate sync, rather than composite (which is I think what the AVGA defaults to).  Either polarity should work, but I've had good results with positive going sync (both H and V).

jarrett

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Re: 27" Betson won't sync -- advice needed
« Reply #2 on: August 01, 2012, 12:04:43 pm »
Ultimarc has a "tri sync utility" that you may need....

I'm pretty sure it's not a software problem. The monitor doesn't even sync on the BIOS screens when the machine is booting. Also, I can reproduce the problem with other computers, one of which is has a brand new ArcadeVGA. This cabinet worked fine for about seven years, and then just quit on a hot day.

I made a video to best illustrate the issue:

MonMotha

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Re: 27" Betson won't sync -- advice needed
« Reply #3 on: August 01, 2012, 12:26:49 pm »
Well, that's an interesting one...

The BIOS text is generally 640x400 @ 70-72Hz, so it's an oddball and may dip slightly below the monitor's "VGA" range and into it's "medium res" range.

Are you sure that your sync format (separate/composite + polarity) is the same between desktop (640x480p/800x600p) and low res modes?  The monitor should accept darn near anything, but if it's different that at least gives a path to explore in terms of what's going on.

Does the monitor make any weird noise while it's doing that?  Does tapping (firmly but not too hard - don't use a hammer or go Mike Tyson on it) on the frame of the monitor or side of the cabinet have any effect?  Any events that could have caused this aside from "hot day", or did it just start doing it randomly?


jarrett

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Re: 27" Betson won't sync -- advice needed
« Reply #4 on: August 02, 2012, 07:22:52 pm »
Are you sure that your sync format (separate/composite + polarity) is the same between desktop (640x480p/800x600p) and low res modes?

I don't know what the sync format is or how to find out. Whichever format it is probably worked before; I didn't change it.

I applied percussive maintenance to the cabinet, but there was no visible effect.

The monitor makes an unhappy whine when it's not syncing. If you turn your speakers up really loud you can hear it on the YouTube video.

I'm fairly certain a component has failed on the monitor chassis. I don't know how to figure out which or how to replace it.

  :cry:

MonMotha

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Re: 27" Betson won't sync -- advice needed
« Reply #5 on: August 03, 2012, 01:09:39 am »
Check Q707, Q706, C705, Q709, Q708, and C709.