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| Green background on monitor |
Posted by: mac2geezer on 2007-11-08 19:15:31
I recently stuck an E-Machines Double Color LX video card in my Mac IIfx, cabled through a VGA adaptor to a 17 in Sylvania CRT monitor. Works fine, but all resolutions except 640x480 have a green background..doesn't really hurt readability but is annoying. Is this the sync on green problem or something else?
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Posted by: SiliconValleyPirate on 2007-11-09 00:15:23
Sync-on-green usually gives an overall green hue/tint to the picture. If only the background is appearing greenish (as in the grey desktop background) it is possibly just poor definition on the monitor with all those little black & white dots. Try bringing the screen resolution down and see if that cures it, or edit the desktop pattern and set it to all white or all black and see if that effects it.
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Posted by: Charlieman on 2007-11-09 12:42:41
Try cleaning all male connectors in your video data chain -- alcohol, methelated spirits, electrical contact cleaner will all work. Use an old toothbrush to get at the pins.
If that fails try a different Mac-->VGA converter. Or if the VGA monitor cable is swapable, try one with better shielding. Thicker diameter cable (external diameter) usually means better internal shielding.
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Posted by: MacMan on 2007-11-09 14:20:10
Unfortunately this problem seems to affect many Mac II series machines when using Nubus video cards with VGA multi-scan monitors. My IIcx does the same with the Acorn monitor it is connected to, but it seems to work fine on all Apple-branded displays.
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Posted by: mac2geezer on 2007-11-09 14:47:46
Thanks to all for the replies. The green tint is there at all resolutions...640x480,832x624,1024x768...and changing to black and white makes no difference, nor does editing the desktop background pattern. I will try cleaning all connectors, but unfortunately the video cable is hard wired to the monitor and I only have the one Mac-VGA adaptor.
As I said, readability doesn't suffer, it's just annoying, but since the monitor was cheap (ie, free) I'll not complain too much.
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Posted by: SiliconValleyPirate on 2007-11-09 14:59:25
if it's definitely only the background and has perfectly white windows and menus then it's got me stumped. However, E-Machines were a branch of Radius and I know practically all Radius and Supermac NuBus video cards use SoG.
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Posted by: Charlieman on 2007-11-11 13:22:32
Most NuBus video cards do separate sync (the best solution for analogue video) by preference, falling back to combined sync or sync on green, depending on the capabilities of the monitor. Most monitors use separate sync or combined sync, hence the requirement for those special adapters for the IIci built-in video etc.
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Posted by: SiliconValleyPirate on 2007-11-11 13:32:23
Most NuBus video cards do separate sync (the best solution for analogue video) by preference, falling back to combined sync or sync on green, depending on the capabilities of the monitor. Most monitors use separate sync or combined sync, hence the requirement for those special adapters for the IIci built-in video etc. In my experience using Radius Thunder cards and SuperMac cards they actively use Sync-on-Green. In fact the Thunder cards only support 2 resolutions out of the 20-odd they provide in Separate Sync mode. Off the top of my head they are 1024x768 and 640x480, I think.
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Posted by: mac2geezer on 2007-11-12 11:27:38
if it's definitely only the background and has perfectly white windows and menus then it's got me stumped. However, E-Machines were a branch of Radius and I know practically all Radius and Supermac NuBus video cards use SoG. It's not just the background; the windows and menus have a slight green tint also. So I guess that means it's the sync-on-green problem, even though I'm not sure of the exact details of that. If someone wants to give me a short tutorial it woud be greatly appreciated.
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Posted by: tomlee59 on 2007-11-14 17:27:39
WIthout a photo, it's hard to say too much for certain. Your problem could be caused by many things, including a weakened crt. The red gun often weakens first, because it's driven the hardest (because the human eye is not sensitive there, and red crt phosphors tend to be of low emissivity, the red gun is typically cranked up pretty high, leading to somewhat faster wearout).
If you eventually determine that a weak red gun is the problem, here's what to try: Inside the monitor are several adjustments for settng beam currents. If you're lucky, they're labeled (in many, even the potentiometer shafts are helpfully color-coded). First note or mark their initial positions. Then crank up the red and/or blue one (or crank down the green one; or do both). If you're lucky, you'll be able to get a decent white balance without degraded focus.
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Posted by: mac2geezer on 2007-11-15 09:30:22
The monitor came from a Windows system where it showed none of the green tint problem, but one of these days I may open up the case and try the tweaks. Trying to set the color balance via the on screen controls doesn't fix the problem, so not sure tweaking the internal pots will help. It's definitely a low priority around here; it's just a second monitor on the IIfx.
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Posted by: tomlee59 on 2007-11-15 15:12:35
Given that it doesn't display this problem when connected to a PC, I'd leave the internal adjustments alone. It sounds as if your problem lies elsewhere.
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