NON-CRT Displays that support 15KHz and 25KHz resolutions

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    • FYI, I tested My Model 2 boards with the LCD1970NX last night, and they're EXTREMELY washed out- I need to add resistors to the RGB output of the Model2 to get it down to the 0.7v range, although this is somewhat of a norm for JAMMA and similar.
      The image was stable and fit on the screen great however!
    • Darksoft wrote:

      I guess 16:9 is also acceptable. Anyone can provide some specific models?
      To my knowledge no one has ever manufactured an LCD over 21in with a 4:3 aspect ratio. the 20in and 21in 4:3 LCDs are incredibly rare (only 2 or 3 monitors this size and aspect ratio exist) and none of them to my knowledge support 15K or 25K resolutions.

      For my research I looked specifically for LCDs in the 19in-24in rage from brands known to have some support for 25K resolution modes. I looked up the spec sheet for about 100 different LCD models and listed everything I found on page 2 of this thread. I don't think I came across anything in the 26in+ range, the closest I found was the BenQ G2411HD and the ViewSonic VG2437Smc which are both 24" LCDs. Even if the spec sheet claims support still I'm skeptical if support exists since chances are 99% of users wont be using the display for that. 26in is kind of the magic number were you jump from being a big "monitor" to a small "hdtv" and I think once you make that jump the support for 25K likely falls off a cliff.

      It's also worth noting that the NEC 1970 that both I and Defor are using DOES NOT officially support 15K or 25K resolutions, even though it works.

      TLDR: I haven't come across any 26in+ 25K capable LCDs, nor have I found any indication that anyone else has even looked for one yet. you might have to to just look up spec sheets and take a gamble.

      EDIT: A quick google search for "27in monitor KHz" turned up two models that CLAIM to support 24K modes:
      Asus PB278Q
      HP EliteDisplay E271i
      worth investigating but obviously buy at your own risk. A similar search in the 32in range has turned up nothing.
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      The post was edited 1 time, last by twistedsymphony ().

    • defor wrote:

      Swapped the main logic pcb, and 15k looks nice, no more wierd interlace tearing- some flickering in the interlace as you mention but good enough for casual play/test bench usage.
      I've started a spread sheet to start cataloging this stuff here: docs.google.com/spreadsheets/d…b9MV6R3o/edit?usp=sharing

      for this monitor I was wondering if there is anything on the back label to help differentiate the loder revisions vs the newer revisions without having to check the firmware or take it apart.

      I'm also curious if you tested non-interlaced 15K or 25K sources on the "bad" control board... I'd be curious if the problem is just with interlaced content or just with 15K content, as this monitor may still be useful if it only has a problem with interlaced sources.
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    • So I was doing some work on my DDR PC over the weakend and since it's setup with CRT_EmuDriver I decided to go through the list of 102 default resolutions and see what worked on the NEC 1970NX...

      240x224@60p - out of range
      240x240@60p - stable
      248x224@60p - out of range
      248x240@60p - stable
      256x224@60p - out of range
      256x240@60p - stable
      264x224@60p - out of range
      264x240@60p - stable
      272x224@60p - out of range
      280x224@60p - out of range
      280x240@60p - stable
      288x224@60p - out of range
      288x240@60p - stable
      296x224@60p - out of range
      296x240@60p - stable
      304x224@60p - out of range
      304x480@60p - stable
      320x200@60p - stable but letterboxed
      320x200@75p - stable
      320x224@60p - out of range
      320x240@60p - stable
      320x240@75p - stable
      328x224@60p - out of range
      336x240@60p - stable
      344x240@60p - stable
      352x224@60p - out of range
      252x240@60p - stable
      360x224@60p - out of range
      360x240@60p - stable
      368x224@60p - out of range
      368x240@60p - stable
      376x240@60p - stable
      384x224@60p - out of range
      384x240@60p - stable
      400x224@60p - out of range
      400x232@60p - stable (has trouble auto adjusting and states out of range even though picture displays)
      400x240@60p - stable
      400x248@60p - stable
      400x300@60p - stable (large black bar on top)
      400x300@75p - stable
      416x224@60p - out of range
      432x224@60p - out of range
      432x240@60p - stable
      432x248@60p - stable
      448x224@60p - out of range
      448x240@60p - stable
      456x232@60p - stable (has trouble auto adjusting and states out of range even though picture displays)
      456x240@60p - stable
      464x224@60p - out of range
      480x224@60p - out of range
      480x240@60p - stable
      480x464@60p - stable (small black bar on top)
      480x480@60p - stable
      496x224@60p - out of range
      496x240@60p - stable
      496x480@60p - stable
      512x224@60p - out of range
      512x240@60p - stable
      512x384@60p - stable (uneven letterboxing)
      512x384@75p - stable (small back bar on top)
      512x400@60p - stable
      512x432@60p - stable
      512x448@60p - stable
      512x480@60p - stable
      544x480@60p - stable
      560x240@60p - stable
      576x224@60p - stable
      576x400@60p - stable
      576x432@60p - stable
      600x240@60p - stable
      640x224@60p - out of range
      640x240@60p - stable
      640x400@60p - stable (uneven letterboxing)
      640x400@75p - stable
      640x480@60p - stable
      640x480@72p - stable
      640x480@75p - stable
      648x240@60p - stable
      664x496@60p - stable
      672x224@60p - out of range
      672x240@60p - stable
      704x240@60p - stable
      704x480@60p - stable
      720x480@60p - stable
      800x600@56p - stable
      800x600@60p - stable
      800x600@70p - stable
      800x600@72p - stable
      800x600@75p - stable
      1024x768@60p - stable
      1024x768@70p - stable
      1024x768@72p - stable
      1024x768@75p - stable
      1152x864@60p - stable
      1152x864@70p - stable
      1152x864@75p - stable
      1280x240@60p - stable (but looks terrible)
      1280x720@60p - stable
      1280x1024@60p - stable
      1280x1024@70p - stable
      1280x1024@75p - stable


      In short 224p is unsupported 232p works but the monitor thinks that it doesn't and everything else I threw at it worked pretty well.
      I did notice that most of these resolutions reported as being something else. most of the time the info box would report the resolution at it's nearest double so for instance (15K) 240P was reporting as (31K) 480P. Since this monitor doesn't officially support 15K resolutions I'm curious if this is just a quirk in the hardware design.
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    • I just bought a second (white this time) 1970nx and matching soundbar for my P2 testbed setup, should be here tomorrow...

      So, let's talk 15k...
      When I feed the monitor video from traditional (non 31k/vga sources), while it looks fine, the color is massively washed out- it's my assumption this is due to the voltage levels being way too high, and no compensation inside the 1970NX... I've heard that 220ohm resistors are needed- is this the optimal value to use? Also will the sync signal need to be limited as well?

      I'm thinking to make a simple little box with the sync separator, switchable voltage levels, powered from the speaker power jack that's on the bottom, just to mahe everything simple and self-contained- then I can just run vga cable or BNC3/4/5 to vga
    • defor wrote:

      So, let's talk 15k...
      When I feed the monitor video from traditional (non 31k/vga sources), while it looks fine, the color is massively washed out- it's my assumption this is due to the voltage levels being way too high, and no compensation inside the 1970NX... I've heard that 220ohm resistors are needed- is this the optimal value to use? Also will the sync signal need to be limited as well?
      sync signal: no. the sync signal whether RGB or VGA should be a 5V square wave so there's no need to adjust it.

      When running an RGB signal from a JAMMA board to my PVM over SCART to BNC I put 330ohm resistors on the outputs... this is because the JAMMA standard calls for 0 to 4V range on the color signal output. arcade monitors are tuned for and expect this. the VGA as well as the SCART (and as it seems BNC standard used by PVMs) expects a range of 0 to 0.7V. so the 330ohm resistors are there purely to drop the range down from 4V at the peak to 0.7V at the peak.

      I went though the math and my research on this here: JAMMA to VGA and JAMMA to SCART

      With that said. hooking up a JVS compliant source such as a NAOMI shouldn't require any resistors or other tweaks to the signal I will say that my System 256 even in 31K/0.7V output mode blooms, and I don't trust that it's actually attenuating the voltages down below 0.7V like it should.

      So for the color channels 330ohm resistors seem to be the most appropriate according to math, and my testing. There was a marked improvement going from no resistors to 150ohm, and again from 150 to 220 and I'd suspect that with some games a lower value might be more appropriate.

      you MAY need a sync separator to split the C-Sync to H and V sync. I haven't actually tested a JAMMA board on this monitor yet as I haven't got around to building my VGA cable so I don't know if it can handle C sync on the H pin with no V sync supplied. This isn't a problem with JVS PCBs even in 15K mode because they have separate H and V sync outputs.
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    • Derick2k wrote:

      I picked up an NEC Accusync LCD71V to use on my test bench, hopefully it does the job.
      Do you know something I don't? I don't recall that model coming up and spec sheets list that as 31K and up only.
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    • twistedsymphony wrote:

      Derick2k wrote:

      I picked up an NEC Accusync LCD71V to use on my test bench, hopefully it does the job.
      Do you know something I don't? I don't recall that model coming up and spec sheets list that as 31K and up only.
      Its not listed on the specs, but apparently it does work with 15 & 24khz, read about it on a couple of amiga forums since I was looking for a monitor for my A1200. Took a gamble on it, will confirm once I have a chance to test it.


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    • twistedsymphony wrote:

      sync signal: no. the sync signal whether RGB or VGA should be a 5V square wave so there's no need to adjust it.
      When running an RGB signal from a JAMMA board to my PVM over SCART to BNC I put 330ohm resistors on the outputs... this is because the JAMMA standard calls for 0 to 4V range on the color signal output. arcade monitors are tuned for and expect this. the VGA as well as the SCART (and as it seems BNC standard used by PVMs) expects a range of 0 to 0.7V. so the 330ohm resistors are there purely to drop the range down from 4V at the peak to 0.7V at the peak.

      I went though the math and my research on this here: JAMMA to VGA and JAMMA to SCART

      With that said. hooking up a JVS compliant source such as a NAOMI shouldn't require any resistors or other tweaks to the signal I will say that my System 256 even in 31K/0.7V output mode blooms, and I don't trust that it's actually attenuating the voltages down below 0.7V like it should.

      So for the color channels 330ohm resistors seem to be the most appropriate according to math, and my testing. There was a marked improvement going from no resistors to 150ohm, and again from 150 to 220 and I'd suspect that with some games a lower value might be more appropriate.

      you MAY need a sync separator to split the C-Sync to H and V sync. I haven't actually tested a JAMMA board on this monitor yet as I haven't got around to building my VGA cable so I don't know if it can handle C sync on the H pin with no V sync supplied. This isn't a problem with JVS PCBs even in 15K mode because they have separate H and V sync outputs.
      Thanks for the feedback-Sounds like mostly I was right in my logic :)
      I get the overbought when I use 15k on the 2x6 with the voltage dip set- clearly this isn't a big deal, but other things I commonly work on (Model 2 for example) don't have that option...
      As far as sync separation goes, I'm planning to implement some switching to switch between SOG, CSYNC, and Separate- the 1970NX definitely does not support CSYNC- I've yet to test SOG, but I'm expecting no support there either, but adding an LM1881 or similar to the setup isn't a huge problem.
    • I don't know what kind of voltage levels come out of the RGB port on Model 2 and Model 3 games. those are kind of in a weird spot between JAMMA and JVS. you could probably test it by measuring the voltage while showing a full solid color on the screen in test mode. (ie: display a full red screen and test voltage on the red pin, etc.)
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    • defor wrote:

      Another LCD1970NX firmware version to add to the pile:

      Verified GOOD:
      F/W ID C59SLP10
      F/W VER. 1.1.10


      Verified BAD:
      F/W ID C39SAP10
      F/W VER. 1.1.12


      F/W ID CB9SSP10
      F/W VER. 1.2.05

      Maybe the good firmware can be flashed to over the ones that dont work?!


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    • This makes me wonder if other LCDs could be "hacked" for better resolution support, or even to bypass some image processing for lower lag.
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    • if by "better resolution support" you mean "more resolution options", then yes- most of the time they use off the shelf analog to digital converters with a custom rom, and with some work, this CAN be modified to do what you speak of...
      The downside is that every monitor's gonna be different and need a custom rom hacked/developed for it.

      If you look on ebay,there's a few vendors out of China that will, given a part number for an lcd panel, give you a fully working hdmi, dvi, vga, or whatever interface, wired up and ready to just plug into the bare panel.. some of them MAY have converters that will do low and medium res video as long as the firmware is setup to do it.. but the video chips on the boards will need the capability as well.

      the good news? we know that gm5221-lf based monitors should at least in theory support everything here.