Build Your Own Arcade Controls Forum
Main => Monitor/Video Forum => Topic started by: MTPPC on May 17, 2012, 08:55:11 pm
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I know people talk about how you could damage a 15KHz monitor by pumping 24Khz into it, but my ms. Pac-mame with a WG7000 gets a good dose of it every time I boot up and it seems none the worse for wear.
So what I am asking is if anyone ever damaged a monitor by overclocking the sync and if so what was the brand and circumstance?
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Are you talking about the BOOT, BIOS and Windows loading Screens?, are they all 24khz then?
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All the images displayed up until the video card driver is installed are at 24Khz. After the last 24KHz screen, the black screen with a mouse pointer shows up for just a moment before the interlaced 640x480 desktop (at 15KHz). Then my MALA frontend autostarts.
The j-pac will take those 24Khz screens and cut them into to side by side identical images, but this machine I'm talking about doesn't have a j-pac.
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"... is right up there with "a cap kit fixes everything."
:laugh2: Mmmm. Sounds like a greate name for a product. "Magic Cap Kit" "It'll fix whatever is ailing your monitor"
DrArcade
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To be honest i hadnt even though of the Windows boot screens outputting a 24khz signal, now ive been enlightened im scared to turn on my nice new CGA monitor :cry:.
Is there away (other than not turning the monitor on straight away) so that none of the boot screens are displayed. I know the ArcadeVGA cards have a feature that doesnt show boot screens
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You certainly can break some monitors by inputting a frequency outside of what they can handle. Whether a monitor is sensitive to this and what happens depends on the design of the monitor. Digital monitors will almost all shut down. Usually, if something breaks, the HOT just dies, but sometimes other stuff breaks, too.
The bootup screens on a PC are not 24k, they are 31k (VGA). Handily, this is exactly double what a standard res arcade monitor is designed for (15-15.5k). Just about every monitor I've found designed for that range will happily lock it's PLL onto every other sync pulse giving the classic "double screen" effect. If your monitor is reliably doing this, you should generally be fine, but some monitors will apparently dutifully try to run all the way up at 31k, usually with the result being a blown HOT.
Dumping 24k into a 15k monitor can be a problem, though. What happens will depend on the monitor, but sometimes you can nudge the horizontal operating frequency outside the range of what the actual output stage can deal with, and things break. I wouldn't say it's overly common, but I've certainly done it (by accident, and to an old fixed frequency workstation monitor, not an arcade monitor). It was easy enough to fix, at least.
I don't know if the JPAC actually does an every-other-pulse output or not. It's often not necessary. The monitor will do that for you.
FWIW, there's less inherent "protection" on most monitors designs against weird vertical frequencies. Incidentally, 240p at ~90Hz works out to ~24kHz, but if you actually try feeding that into a medium res arcade monitor, you probably won't like the results (but then again, you may be fine). Note that many PCs run their bootup screens at ~72Hz. The line count is dropped to ~400 visible lines to keep the horizontal scanrate at ~31kHz. This will probably make some monitors unhappy.
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I know my Pentranic CGA monitor display what appears to be a broken up super fast rolling screen (you cant read any of the boot screen and when the black screen appears just after the 'Windows XP loading' screen you can see 4-6 mouse pointers on the screen with a double picture so 4-6 mouse pointers each side) and appears to be showing double (side by side) pictrue up until it boots ito windows.
Is this the monitor protecting itself or will it only do damage over time?
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If you are using a j-pac, the j-pac halves the 31KHz signal and splits the screen. I have never seen a CGA monitor do this on its own, but I am sort of new to arcade monitors. Again, I am asking for specific and credible examples of damaging a monitor. My WG7000 has a brief exposure to "hypersynch" everyday and it seems none the worse for wear. It never splits the screen and just acts like a total loss of synch while it happens. Please, if you have damaged a monitor with "hypersynch" please let us know the monitor and what generated the damaging signal.
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I power up my monitor (WG7000) after the PC boots, so its not an issue for me. But I've powered everything up at the same time and it doesn't hurt anything.....it just doesn't sync. If you can hear a nasty squealing sound from the monitor when it gets fed out of range sync, best to not do that (risk of damage).
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The Sony PVM-25 monitors will split the screen at 31khz. I have a late 90s Compaq 15" PC CRT that goes from 31-48khz, and it will split 15khz resolutions. Very handy sometimes.
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no.
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If you plug in a 2nd video card, like an old PCI (not pci-e) the bios screen is hidden. This saves you some time spent on a freq that your monitor doesn't like.
I can't remember if the windows boot screen is hidden as well....getting too old. I'm sure someone will chime in.
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Yes, I have. Copying my post from an old thread on this same subject:
Has anyone ever actually, verifiably fried a monitor by feeding it a bad signal? Somehow I doubt it.
I have done this.
I had a Nokia workstation monitor that would only accept a few resolutions. I had advancemame set up on it playing in double refresh/native mode.
If I left Super Street Fighter II turbo setting in attract mode for too long it would crash. It's a glitch in advancemame with that particular game.
I left the room and the game crashed, sending the OS back to the desktop. In this case the desktop was set to 1024x768@120hz. This was the resolution I was using on on my main pc.
I had switched the video cable from my dekstop monitor to the nokia one to test the monitor at high refresh rate/low res modes.
When it switched back to the desktop the monitor would squeal and show squiggly lines. I usually caught it and turned the monitor off and then switched the cables back to the desktop monitor.
but one day I forgot that Street Fighter could crash and just left it in attract mode. When I came in the room after a while my monitor was off and had a blinking orange light.
When I hooked the pc back up to my desktop monitor I could see the game had crashed.
The Nokia monitor never worked again.
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If you plug in a 2nd video card, like an old PCI (not pci-e) the bios screen is hidden. This saves you some time spent on a freq that your monitor doesn't like.
I can't remember if the windows boot screen is hidden as well....getting too old. I'm sure someone will chime in.
Actually thats got me thinking instead of plugging in a 2nd GFX card, my GFX card has 2 DVI sockets so if you plug your arcade monitor into the 2nd DVI socket and tell windows to display the desktop on display 2 in theory the arcade monitor wont show any of the BIOS or windows loading screen as that will all be sent to display 1, will that work?
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If you plug in a 2nd video card, like an old PCI (not pci-e) the bios screen is hidden. This saves you some time spent on a freq that your monitor doesn't like.
I can't remember if the windows boot screen is hidden as well....getting too old. I'm sure someone will chime in.
Actually thats got me thinking instead of plugging in a 2nd GFX card, my GFX card has 2 DVI sockets so if you plug your arcade monitor into the 2nd DVI socket and tell windows to display the desktop on display 2 in theory the arcade monitor wont show any of the BIOS or windows loading screen as that will all be sent to display 1, will that work?
Mmmm. Maybe. I think it depends on video card make and model. Try it. Report back.
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So Jack Burton is the only person who reports actually damaging a monitor. The monitor he damaged was not an arcade monitor and he dumped 120KHz @ 1024x768 into it. My conclusion is that nobody is damaging their CGA arcade monitors by dumping the 25KHz boot up screens into them.
Good.
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I have seen svga and vga signal kill hantarex polo 1 monitors horizontal output transistor,never seen 24khz damage a cga chassis though.
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So Jack Burton is the only person who reports actually damaging a monitor. The monitor he damaged was not an arcade monitor and he dumped 120KHz @ 1024x768 into it. My conclusion is that nobody is damaging their CGA arcade monitors by dumping the 25KHz boot up screens into them.
Good.
[to re-iterate what others have said] 31khz
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So Jack Burton is the only person who reports actually damaging a monitor. The monitor he damaged was not an arcade monitor and he dumped 120KHz @ 1024x768 into it. My conclusion is that nobody is damaging their CGA arcade monitors by dumping the 25KHz boot up screens into them.
Good.
As I said (you apparently missed it), I've done it too, but also to an old fixed-frequency workstation monitor (for a Sun Sparcstation IPX) by dumping 1600x1200 into it (it expects about 900-1000 lines at 60Hz). It was close enough to "correct" that I didn't have severe geometry problems, so I didn't think to double-check my config. It died after about 10 minutes.
Also, to reiterate the above post: PC boot screens are 31kHz, NOT 25k. 31k happens to be a special case since it's exactly double what a normal arcade monitor expects. YMMV with actually putting 25k into a 15k monitor.
In general, if it "doesn't sync" or gives you a "double image" at 640x480, you're probably not breaking it (but no guarantees). If it displays a somewhat intelligible picture, possibly with bad geometry (pincushion will often be very extreme) and/or makes awful noise, you're probably going to break it.