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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!simtel!news.dacom.co.kr!news.kreonet.re.kr!usenet.kornet.nm.kr!ames!hookup!olivea!decwrl!pa.dec.com!nntpd.lkg.dec.com!usenet From: Jon Jenkins <jenkinsj@ozy.dec.com> Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Oddball Monitors Date: 18 Nov 1995 06:18:47 GMT Organization: Digital Equipment Corp Lines: 238 Message-ID: <48jts7$i65@nntpd.lkg.dec.com> References: <78741235wnr@falstaf.demon.co.uk> NNTP-Posting-Host: ozyd13-p3.ozy.dec.com Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="-------------------------------13658589141037190445963788868" X-Mailer: Mozilla 1.1N (X11; I; BSD/386 uname failed) To: robin@falstaf.demon.co.uk X-URL: file:/root/convert.cir This is a multi-part message in MIME format. ---------------------------------13658589141037190445963788868 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii The following may be of some use Jon -- ---------------------------------------------------------------------- Name: Dr Jon Jenkins Location: Digital Equipment Corporation NaC Voice/Fax: 61-7-55-75-0151/100 Burnett Place, Research Park, Inet: jenkinsj@ozy.dec.com Bond University, Gold Coast Close Proximity: "HEY YOU !!!" QLD, AUSTRALIA 4229 "Daddy, what's outside the Universe?" (My 5 year old.....) ----------------------------------------------------------------------- ---------------------------------13658589141037190445963788868 Content-Transfer-Encoding: 7bit Content-Type: text/plain Notes on VGA->RGB conversion: Be warned some monitors (older SUNs in particular) use RGB+CSYNC i.e. 4 connections and not "sync on green" RGB. There may be a jumper inside the monitor to change this but you should seek assistance to make any changes of this nature. Alternatively you can just take the CSYNC signal from below and use it. I have not blown up any monitors in my testing but it is possible to blow up a monitors input stage. If you are in any doubt get someone who knows what they are doing to do these alterations. ------------------------------------------------- IF the video card you are using is a standard VGA output: (Im using a Diamond stealth 64 VRAM but I have also tested this on my wifes Tseng Labs SVGA card) 1: RED video 2: Green video 3: blue video 4: monitor id bit 2 5: Ground 6: red return 7: green return 8: blue return 9: NC 10: sync return 11: monitor id bit 0 12: monitor id bit 1 13: H sync 14: V sync 15: NC I join all the "returns" together with the ground on the small PCB and use that as a common ground for the RGB cable to the monitor. You can use separate if you want to but you should join the green return and sync returns together. I did find some small shadowing if I didn't group them all together. Just a note, when you set up your video card in Windows OS/2 or whatever, set it to whatever is closest to the monitors resolution as a first approximation. My Diamond gives me a lot of freedom for adjustment but some cards dont. As a general rule Workstation monitors are not interlaced. I use a DEC VR260 (1024x864@60Hz) at 1027x768@70Hz or a VR319/320 (1280x1024@72) exactly as per the setup menu. Dont forget you CANNOT do 1280x1024 with a 1M RAM video card!!! Note: Your standard VGA monitor may not like this frequency so either disconnect it *VERY* quickly or before you actually set the video card to the new mode (i.e. put the OK as the active control in Windows and then connect the "big" monitor and hit return). My Diamond setup gives me 10 seconds to do adjustments. When you exit you will probably have to select the new mode with your old VGA connected again but from then on every time you start Windows you will be able to view it in "big" mode. Note the workstation monitors are not multisync monitors so all you see when you boot up DOS is garbage until Windows starts, I put "win" in my autoexec.bat file. If all else fails you can set the video card to the closest resolution i.e. 1024x768 for a 1024x864 monitor and and adjust the Hsync and Vsync frequencies on the monitor. These may be accessible from the outside either as dials or by ***PLASTIC*** screwdriver access. DO NOT ***REPEAT*** DO NOT use a metal screwdriver for accessing these recessed sync controls. Alterntively they may be inside the monitors case. ****************WARNING*************** If you have to open up a monitor to do this adjustment be warned: monitors have very *LETHAL* voltages inside. You will not get a second chance!!! Unless you know exactly what you are doing get someone else who does to do this adjustment. ****************WARNING**************** Note there is a danger here: During testing I had set up the monitor and for some reason it did not work so I couldn't see what was going on: My ol VGA wouldn't work either either so I had to find the cards .ini files and edit by hand to get back to useable video !! Make a backup of the video/system .ini files just in case this happens. For FreeBSD/XF86 setup is trivial, the lines for a DEC VR260 and a DEC VR320/319 using an XOR (or an OR) gate are: Modeline "1280x1024" 130.81 1280 1312 1472 1696 1024 1027 1030 1063 +hsync +vsync Modeline "1024x864" 69.2 1024 1040 1168 1272 864 864 867 904 +hsync +vsync For a NAND gate change the syncs tp -hsync and -vsync See your monitor manual for the frequency, porch and blanking details ------------------------------------------------------- The circuit to do this is as follows: Note. 1: you may be dealing with 135MHz sqaure waves so there are lots of high frequency stuff around; use good RF practices. 2: the coupling capacitors are a safeguard to start with I dont use them cause they caused shadowing around sharp colour changes (the ol RC effect). 3: Use the XOR gate first as a test but you may need other gates to actually get it working 4: A CRO will be handy (necessary!) for final adjustment. 5: Make the device is as close as possible to the video outlet on the VGA card. 6: Take the 5V from the PC power supply inside the box. I just hooked one of the spare connectors which I also use for an external fan (5V pentiums being the heaters they are!). Make sure (check it again!!) (and again!!!) you dont get 12V else say "goodbye" to your monitor!!! 7: You must use a VN10KM or other SMALL SIGNAL N CHANNEL ENHANCEMENT MODE MOSFET others will not work !!!!!!!! +5.0V | / \ VR1 (1k carbon mini pot) 33uF tantalum | ~0.3V DC in porch area GREEN------|----||-----|--------------------|-----GREEN to monitor| |----||-----| | .1-.01uF ceramic | | gnd | | | / | \ 47k | / _| HSYNC---|----|-------\ | | GATE |------CSYNC----|----|| VN10KM or similar small VSYNC---|----|-------/ / |_ N channel enhancement MOSFET / | \ | \ / gnd / 47k \ 47k | | gnd gnd HSYNC, VSYNC and CSYNC are grounded with 47k carbon resisitors GATE=LS or HC types, HC preferred. OR: logic is: when both syncs 0 the gate output is 0 and the FET is off. When either or both syncs go +ve the gate drives the FET on which pulls the green to ground. NAND: logic is: when both syncs are logic 1 the gate output is 0 and the FET is off. When either sync goes to 0 the gate output drives the FET on and pulls the green output low. This is the most common form of sync output from PC SVGA cards hi res mode. XOR: for -ve or +ve logic sync and hysnc during vsync logic is: when both syncs are 1/0 the gate output is 0 and the FET is off. When the Hsync changes state the FET turns on pulls green to ground. When the Vsync changes state the output is gated by the Hsync and if your video card produces Hsync during Vsync (most do) then the green signal will be a square wave with a non 50% duty cycle. Some monitors require this Hsync action during Vsync otherwise the horiz PLL loses lock. Capacitors are optional, I dont use them now but I used them during testing. They will cause a shadow effect due the the 75ohm resistances at either end of the circuit causing a DC bias buildup on the green signal. Get a CRO an adjust the variable resistor so that the green levels to 0.3V during video and 0.0V during sync pulses. I used standard 74HC 14pin DIP gates and 14pin DIP sockets originally so that I could change gate types (OR/XOR/NAND) easily. Good luck ---------------------------------13658589141037190445963788868--