Using VGA TFT monitors on HP 9000/300 series
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How do you guys connect your 9000/300 or 400 systems to a monitor. The old HP (Sony) monitors are bulky and heavy not very handy if you’re not pledged with a lot of space. I’m using a little circuit based on a LM 1881N sync separator. It generates the necessary sync signals form the green video signal, and makes it possible to use a stock vga screen. I’m curious how you’re connecting a monitor to a 9000/300 system.
-Rik
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Paul Berger
Rik, I am currently using a flat screen monitor, Samsung SyncMaster 515V, that supports sync on green, on my 380. For my 9920 I am using a HP green screen composite monitor. I would be interested in seeing your sync seperator circuit, if you are willing to share. Paul.
On 2017-01-22 5:52 PM, Rik Bos wrote:
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I will, but i have to edit the diagram. If you can process MultiSim and Ultiboard files I’ll upload those to.
-Rik
Van: VintHPcom@groups.io [mailto:VintHPcom@groups.io] Namens Paul Berger
Rik, I am currently using a flat screen monitor, Samsung SyncMaster 515V, that supports sync on green, on my 380. For my 9920 I am using a HP green screen composite monitor. I would be interested in seeing your sync seperator circuit, if you are willing to share. Paul.
On 2017-01-22 5:52 PM, Rik Bos wrote:
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The HP 2035 TFT Monitor also has sync-on-green on its VGA connector and as an additional bonus it has a composite signal input using a cinch connector. Its VGA input works well with the RGB outputs of e.g. a 9000-332 (1024x768). The composite input works well with the 82163A interface for HP pocket and BASIC calculators or the HP 86 Series-80 machine. However the monitor does not work very well wíth the standard monochrome graphics board 98204 of the 9000/200/300 machines. The menu lines at the bottom are missing and the monitor loses its image every 2-3 minutes to resync again. Maybe a sync splitter could help. Martin
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Paul Berger
Martin, Is that a 98204A or B? the 98204A is US TV standard while the B has a much faster horizontal rate. Paul.
On 2017-01-27 8:44 AM, Martin Hepperle
wrote:
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ah sorry, my experience is only with the European "98204 B" card. Martin
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Ansgar
I currently use a NEC 1770NX (the "NX" is important!) and am quite satisfied. Not every monitor with sync-on-green works well, this one does (and looks damn good). I guess for proper operation the horizontal sync capabilities are essential. Jon from hpmuseum once said (and it is still on his web site) that the NEC LCD1800, LCD1810, LCD2010 and LCD1830 are good replacements for the higher resolution HP monitors, but I personally like the more compact 17" and especially the more decent 1770NX. The NEC starts hsync at ~30 kHz (original VGA timing). The low res monochrome video boards, however, provide a 15 kHz hsync, which is supported only by some LCDs with composite video input. My DELL for example has that kind of input, but still does not detect the output from the low res HP 300 monochrome boards, So I am glad I still have my 82913A at hand. I also tried with an LM1881 sync splitter, but it cannot replace a true sync-on-green input circuit (the LM1881 does not correct the wrong black level, or shall I say dark-green-level...).
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I’m using a Belinea 10 17 05 and Samsung SyncMaster 720N with both medium (1024 x 768) and high (1280 x 1024) resolution cards. I haven’t noticed any problem with the green color. I know the 1881N is susceptible for parasitic capacities on the input but that shouldn’t influence the green color levels.
-Rik
Van: VintHPcom@groups.io [mailto:VintHPcom@groups.io] Namens Ansgar
I currently use a NEC 1770NX (the "NX" is important!) and am quite satisfied. Not every monitor with sync-on-green works well, this one does (and looks damn good). I guess for proper operation the horizontal sync capabilities are essential. Jon from hpmuseum once said (and it is still on his web site) that the NEC LCD1800, LCD1810, LCD2010 and LCD1830 are good replacements for the higher resolution HP monitors, but I personally like the more compact 17" and especially the more decent 1770NX. The NEC starts hsync at ~30 kHz (original VGA timing). The low res monochrome video boards, however, provide a 15 kHz hsync, which is supported only by some LCDs with composite video input. My DELL for example has that kind of input, but still does not detect the output from the low res HP 300 monochrome boards, So I am glad I still have my 82913A at hand. I also tried with an LM1881 sync splitter, but it cannot replace a true sync-on-green input circuit (the LM1881 does not correct the wrong black level, or shall I say dark-green-level...).
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Ansgar
I'm not an expert on this, but I guess the dark green effect depends on the nature of the sync signals. The sync signal is added to the green video signal, but the sync can be either a high pulse or a low pulse (depending on the video board). If you have a high pulse on sync, you probably will not notice any effect on the black level (the high pulse is restricted to retrace), whereas if you have a low pulse, the sync signal is high during a normal scanline run and low during retrace. Take it as a weak trial for explanation. In fact the LM1881 does not remove the sync from the video signal (it actually has no video output), but replicates the sync info to its sync outputs. But it should be possible to subtract the composite sync (coming from the LM1881) from the original green video signal by another circuit (e.g. opamp) and so achieve a "clean" green signal. -Ansgar
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Paul Berger
I have an NEC EA192-M when I got it I had initially tried it with a 1024x768 98545A card and was disappointed to find it would not sync giving an out of range message. The native resolution of this monitor 1280x1024 so today I decided to try it with the 1280x1024 A1416A card an was very happy to find that it synced and looks nice. I did have to adjust the position a little but other than that it works great. Paul.
On 2017-02-06 4:32 PM, Ansgar wrote:
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Mark Bielman
Hello Group,
Looking for an assist and 'perhaps' this is a good place to start. I am using an HP 35731B mono (green) monitor for my "Desktop Integral" (Model 9808, never produced) which has no built-in display. This monitor is old and just barely OK. (probably needs all the electrolytics replaced.) I am also trying a 35731B color monitor which is slightly better. BUT, would like to go to a "VGA TFT". (taking up less space is always a bonus too) I have a couple of composite-to-VGA converters but they do not work. (and a flat screen with both VGA and comp video inputs but no luck there either - not multisync.) Turns out my horz rate in the neighborhood of 25 kHz. So I am wondering if the LM1881 might work to drive one of the monitors suggested here. (the 220 may also have this horz freq. As I recall, my old CRT monitors work there too.) Any suggestions? thx Mark
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Mark,
for Series 9000/200/300 and Series-80 I am using HP 2035 TFT monitors with a simple cable linking Composite to VGA-green ("sync-on-green"). This works quite well, with the usual limitation that the scaling may be slightly uneven, depending on the match of resolution ratios. This monitor also has a composite input (rare for TFTs), but this does not work for these rates. So the trick is to route the composite signal to green (and to pull G and B low to get a black background). The monitors can be found second hand (for about $20-40) Another gadget which works is a GONBES GBS-8200 converter for arcade-game systems ($20-40 on eBay), but this may cut a few lines off (on my HP-9000/300), depending again on resolution. They come in different variants having 1 or two VGA outputs. There is also a professional version in a black metal casing ($100+) which is said to be even better. The usual house-hold ($15) composite-VGA converter boxes usually do not work. Martin
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Ansgar
Mark,
you should be aware that most non-vintage monitors have 31.5 kHz as the minimum horizontal sync rate they can synchronize to. Reason behind is the VGA standard, which still is the lowest common denominator. Most monitors today are using standard video chips, which start around 30 kHz. 25 kHz is simply out of range. Some monitors however support 24 kHz, and some even go down to 15 kHz, which is the horizontal sync rate of most monochrome monitors in the late 70s/early 80s (including some from HP). See http://15khz.wikidot.com/ for a list of potential modern "replacements" (did not check them on my own). Some of them also might work with 25 kHz. You also should have an eye on sync-on-green, to allow a more general use for computers with 3-channel RGB output. NEC Multisync 1510+/1510V+ are examples that should work with both 25 kHz and sync-on-green. LCD monitors with BNC inputs (if you need them) are pretty rare, but there are proper cables around, or you can build one on your own. -Ansgar -Ansgar
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Mark Bielman
I picked up an NEC LCD1800, arrived today, but no power supply. Should be here in a few days.
Also grabbed a 10-pack of various BNC/VGA cables for $15. Hopefully I can get something going.
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Mark Bielman
I fired up my 9920 today (has been a while!) and was thinking it had the faster (28kHz) scan rate. Nope! I have the 98204A which is apparently <almost> NTSC. I say
"almost" because the top & bottom are cut off. (I am using LCD security video monitors, not old CRT versions - have one of those and have not tried it) There are 2 DIP switches on the 98204 but no idea what they do. Any ideas on how to "fix" this? A monitor issue? Mark
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Ansgar
Hi Mark,
the standard monitor for the 98204A is the 82913A, which is specified for 15.75 kHz horizontal scan rate. You probably need to find a proper replacement. Concerning the DIP-switches you may check with Tony Duell's schematics for the 98204A. -Ansgar
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Mark Bielman
I tried the NEC LCD1800 monitor on the "Desktop Integral" which runs at (approx) 28 KHz and no luck. The NEC specs say it should work at this scan rate.
Does anyone know... do I have to set up the monitor manually? Also, I am using the "B" input on the monitor. Mark
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Ansgar
Hi Mark,
if the monitor simply ignores the signal (no on-screen-message for wrong input frequency), you probably need to check whether you are using the correct cable which connects the snyc signals from the HP to the right sync inputs at the monitor. As far as I know, there is no documentation for your system, also there is no one else using that type of system, so you need to find out about the pin assignments on the HP side on your own. I recommend using an oscilloscope or logic analyzer for checking the sync signals, if one is available for you. -Ansgar
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Mark Bielman
This is a composite video signal, not RGB. So was hoping the monitor would detect it as sync-on-green.
What I am doing now is using an HP 35741B RGB monitor with composite video driving all 3 RGB inputs. (so it's B&W, not icky green) This works fine except the CRT on the monitor is old and a bit burned. From the computer, I am using a video distribution amp (0 dB gain) so the 3 RGB signals have equal levels. (my 35731B needs new caps I think as it "moves" and makes me sea sick.) I want to try the LCD monitor on my 9000/300 (with a 98550 video card) and see - that should work, right? Mark
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Ansgar
Hmm... there are some more factors to take into account, I guess. HSync pulse may be low or high, same for VSync. In every case, it is quite useful to have a good idea how the signal is really shaped. Some monitors can cope with many settings, some don't. Some monitors expect certain pulse lengths and timings (sometimes documented, sometimes not). Composite video rarely is above 16 kHz (for the sake of the video circuits available at the time), but if you are sure you know the specs of the original monitor for the "desktop intgeral", this is a good starting point. But until you know exactly the specs of both the source signal and the video chip in the monitor, it is like a walk in the dark. Sometimes it helps to identify the the video chips installed and check their data sheets.
-Ansgar
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