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LCD Monitor that supports ST Low Res! NEC MultiSync LCD 1970VX

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This info should be added to every "how do I hook up an ST to a monitor in North America?" thread. I've heard people speculate that some LCD monitors support ST Low Res, but I'd never found one that actually works before. In fact the manual for this monitor says it doesn't go below 31kHz horizontal scan rate, but in reality it does!


I picked this NEC MultiSync LCD 1970VX up for $20, they were a popular office monitor a few years ago and are great quality, just a bit bulkier (has a CFL backlight) and lower resolution (1280 x 1024) than modern LED backlight LCD monitors. People are practically giving these things away, and they work perfectly with the ST!


To connect this up I just wired up the ST's R, G, B, Hsync, Vsync and Ground to the same VGA pins, connecting all the VGA ground pins together. I used a 50 ohm resistor on each of the R, G, and B lines to avoid the colours washing out.


For high res I connected the ST's mono out to R, G, and B with a single 100 ohm resistor in series. Of course I grounded the ST's mono detect pin too. I use a 4-way 4PDT toggle switch to choose low or high res, connecting the VGA RGB to the appropriate pins from the ST and grounding mono detect.


Oh and it supports both 50 and 60Hz! The image aspect ratio shifts a tiny bit, this monitor has hsize, hpos, and vpos settings though so you can tweak the image position.


Example images of low and high res.


post-39360-0-89907100-1412737652_thumb.jpg post-39360-0-31289600-1412737674_thumb.jpg post-39360-0-89213400-1412737689_thumb.jpg

Edited by galax

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This monitor comes pretty close to a real SM124/5, and does colour too, in a much smaller space. It also has that nice LCD perfect flat and squareness, which the old CRT monitors obviously can't match.

 

I've seen LCD monitors handle high res before, but never ST low res. Incidentally my NEC MultiSync 1940CX can handle ST high but not ST low.

 

From the manual for the 1970VX it shouldn't be able to handle 15kHz nor 50Hz, but it does:
  • Synchronization Range
    • Horizontal: 31.5 kHz to 81.1 kHz
    • Vertical: 56.0 Hz to 75.0 Hz

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Yes, medium res is fine as expected, the monitor doesn't know the difference between ST low and medium, sees both as 640x240. Looks better if the image is stretched a bit wider horizontally though.

 

Attached is the brochure for the NEC 70 series monitors, and the manual for the monitor I have. There is no mention of being able to support 640x240 or the horizontal or vertical refresh rates.

 

I wonder if other monitors in this series have this ability to support the ST too, the full series is: LCD1570NX, LCD1770VX, LCD1770NX, LCD1770NXM, LCD1970VX, LCD1970NX, LCD2070VX, LCD2070NX, LCD2070WNX, LCD2170NX, LCD2470WVX, LCD2470WNX.

 

Here's the info display on the monitor in 50 and 60 Hz mode, which contradicts the manuals:

 

post-39360-0-73851300-1412925868_thumb.jpg post-39360-0-35761900-1412925876_thumb.jpg

NEC Multisync 70 Series Brochure_0608.pdf

NEC Multisync1970VX Works with ST Low Res.pdf

Edited by galax

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I thought NEC stopped using the Multisync branding last century... these monitors could come in handy elsewhere as well (Amiga, A8 with VBXE)

 

Also handy that it accepts 50 Hz.

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That is awsome, you got pics of the homebrew connection. :)

 

Yep, I re-purposed a $2 garage sale find VGA switchbox (nice metal case, gave me two VGA outputs for experimentation, and reduced the amount of soldering a bit), both VGA outputs support both colour and mono:

 

post-39360-0-45720300-1412930999_thumb.jpg post-39360-0-13355000-1412931004_thumb.jpg

 

I thought NEC stopped using the Multisync branding last century... these monitors could come in handy elsewhere as well (Amiga, A8 with VBXE)

 

Also handy that it accepts 50 Hz.

 

It seems they kept it going until at least 2008, but yeah I associated the name with the old ST/Amiga monitors that could support different resolutions until I found these used monitors. I suppose anything that outputs a similar horizontal frequency RGB signal would work too, I only have STs to test with though. It'll be interesting to see if anyone else can get hold of monitors in this series and give them a try...

Edited by galax

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Very cool !

 

Does the ST image fill the NEC screen at all resolutions ? I hooked up my MegaSTE to an old LCD (forget the brand) using the cables from Best Electronics, and the mono image only filled the top-left part of the screen. Unfortunately, the LCD offered no options to adjust the size or position, so it wasn't the ideal experience.

 

You mention though, that the NEC has size and position adjustements, but does it give you enough range to fill the entire screen at all resolutions?

 

Now, just to track one of these babies down...

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So this is a direct replacement for a 1224?

 

I finally wired up a cable for my Roland S-50 to 1224, and it works great, but an LCD would mount to a keyboard stand so much better.

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Does the ST image fill the NEC screen at all resolutions ? I hooked up my MegaSTE to an old LCD (forget the brand) using the cables from Best Electronics, and the mono image only filled the top-left part of the screen. Unfortunately, the LCD offered no options to adjust the size or position, so it wasn't the ideal experience.

 

You mention though, that the NEC has size and position adjustements, but does it give you enough range to fill the entire screen at all resolutions?

 

Here's how low, medium and high res look- all have some top and bottom borders (which is nice if you like demos and/or games that use overscan), high res fills the screen width, which is good too as the 640 pixels are exactly doubled to 1280, and has top/bottom black bars.

 

post-39360-0-79765100-1413008477_thumb.jpg post-39360-0-64309800-1413008486_thumb.jpg post-39360-0-60572600-1413008498_thumb.jpg

 

I can only control hpos, vpos, and hsize. Hsize adjusts enough to correct aspect ratio problems, but I can't fill the screen width with the non-overscan 320 pixels in low and medium res.

So this is a direct replacement for a 1224?

 

Better than that, it replaces a 1224 colour monitor, and a high res mono monitor. To change to and from from Low/Med colour and High res mono I just flick the toggle switch (which reboots the ST of course), and the monitor picks up the new resolution. No unplugging cables, or multiple monitors.

Edited by galax

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Switching between 50 and 60Hz, the monitor blacks out for half a second or so while it adjusts. 60Hz shows up as a tiny bit wider by default, but that could be adjusted by changing the vsize.

 

post-39360-0-35034600-1413008923_thumb.jpg post-39360-0-05708200-1413008931_thumb.jpg

 

 

Here's the 'Overscan' demo, which can fill the screen nicely:

post-39360-0-28421600-1413008938_thumb.jpg

 

Most monitors cut off at least some of the overscan area, parts of the demo are cut off (first pic), but they can be seen by changing the vpos (second pic), for example:

post-39360-0-08460800-1413008945_thumb.jpg post-39360-0-82690300-1413008952_thumb.jpg

Edited by galax

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A guy called Troed saw my Facebook post about this, and found a DELL monitor that works too:

 

Thanks for the inspiration. We can add the Dell 2001FP to this list - also a 31-80kHz scanner according to the manual, however, since it has composite and S-Video connectors I (thanks to your post) got the idea to test whether it'd do 15kHz via the VGA connector as well. I already knew it supported ST hi.


Success.

post-39360-0-32390200-1413057001_thumb.jpg

If I switch to 60Hz it changes to "NTSC@60Hz" (which is fine since it's RGB anyway). So yes - 60Hz works.

It's not perfect though. After each "resolution change" the picture is not centered and I have to enter the monitor menu and change both H and V pos to cause it to center the picture. It's the auto adjust that fails, I don't really need to center it manually - it just needs any change for it to "snap" to the correct position.

 

 

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In the modern day, LCD monitors have changed from 16:10 to 16:9 - big reason being cost-saving since it's the same as TVs.

So maybe more monitors than we think might support the slower line rate.

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What about the audio output?

None of the monitors I use have speakers. Mono audio and composite video (for modulator machines) can be split out from one pin each on the ST's monitor port, I'll add RCA sockets to this switchbox sometime. With the STE it's better to use the stereo audio RCA outs on the machine of course. I run the audio into PC speakers.

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None of the monitors I use have speakers. Mono audio and composite video (for modulator machines) can be split out from one pin each on the ST's monitor port, I'll add RCA sockets to this switchbox sometime. With the STE it's better to use the stereo audio RCA outs on the machine of course. I run the audio into PC speakers.

Very true. I must've missed a section mentioning it was an STe and not a stock STm/STf/STfm.

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In the modern day, LCD monitors have changed from 16:10 to 16:9 - big reason being cost-saving since it's the same as TVs.

So maybe more monitors than we think might support the slower line rate.

 

1080p at 60Hz is about 67.5kHz horizontal, 1200 line signals are more like 74.52 kHz. Nowhere near the 15kHz frequencies this 640x240 (detected) signal from the ST uses.

 

Very true. I must've missed a section mentioning it was an STe and not a stock STm/STf/STfm.

 

Oh I have a 520 STM as well, so I will add audio out to the switchbox eventually. When I set it up for some quick testing I used the RF output to an old TV for nice low quality retro audio ;)

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Very cool. Does this work with any of the ready made ST -> VGA adapters that you can buy online?

 

http://www.retrogamingcables.com/atari-st-to-vga-cable-with-sound-for-sale.html

--This one says it is a monochrome only cable. I'm not sure if this actually needs to be wired differently or if they just say that because the color resolution is out of sync for most monitors these days.

 

http://www.best-electronics-ca.com/monadapt.htm

--This claims to handle all three resolutions if you have a compatible multisync monitor, so I am betting this one would work.

Edited by Tenorman

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Very cool. Does this work with any of the ready made ST -> VGA adapters that you can buy online?

 

http://www.retrogamingcables.com/atari-st-to-vga-cable-with-sound-for-sale.html

--This one says it is a monochrome only cable. I'm not sure if this actually needs to be wired differently or if they just say that because the color resolution is out of sync for most monitors these days.

 

http://www.best-electronics-ca.com/monadapt.htm

--This claims to handle all three resolutions if you have a compatible multisync monitor, so I am betting this one would work.

The first cable looks mono only. Mono and colour cables are wired differently; in mono mode the ST outputs its video signal on a single 'mono out' pin. This pin has to be connected to the VGA Red,Green, and Blue pins. In colour modes, the ST's R,G,B are connected to VGA R,G,B. To have a cable that supports both a switch or some other components are needed. The ST is forced into mono mode by grounding the mono detect pin on the ST monitor port- another reason why a cable has to be either colour-only, mono-only, or have a switch to support both.

 

The Best cable looks like a commercial version of exactly what I created with the switchbox, once I have plugged a regular D15 VGA cable in. If I didn't have all the tools and components to hand I'd by this. I'd still make my own after seeing this though, as I can modify and tweak it more easily. One extension I might add is extract Composite Sync from the Composite video on the second VGA port and see if I can get it working with a cheap GBS-8220 scan converter, good to have options ;)

Edited by galax

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Hey can you show how you wired up your cable? (Drawing) Maybe a photo of the "finished" product?

 

Thanks much, I have a hard time wrapping my head around 4TDP switches and wiring. Also, a link to a switch sold by newark or digikey would be cool too.

 

-A.

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Hey can you show how you wired up your cable? (Drawing) Maybe a photo of the "finished" product?

 

Thanks much, I have a hard time wrapping my head around 4TDP switches and wiring. Also, a link to a switch sold by newark or digikey would be cool too.

 

-A.

 

 

I think a circuit diagram might be a bit confusing, so here's a description of the pin to pin connections.

 

Firstly, here's what the number of the two connectors looks like, note which side these are viewed from:

SVGA DB-15 socket looking at monitor from outside (pins are numbered on many sockets)
5  4  3  2  1
 10  9  8  7  6
15 14 13 12 11

ST monitor socket looking at computer from outside:
4  3  2  1
8  7  6  5
12 11 10 9
    13

The simplest ST->VGA cable is just a colour one, everything is just connected straight through. You might need to play with the values of the resistors a bit; too low and the colours wash out (bright red becomes the same as very bright red, etc.), too low and the picture becomes dark and/or noisy:

Colour Monitor Cable
====================

Atari ST                      SVGA DB-15
~~~~~~~~                      ~~~~~~~~~~  
7 (red) ---------[50Ω]------- 1 (red)
6 (green) -------[50Ω]------- 2 (green)
10 (blue) -------[50Ω]------- 3 (blue)
9 (hsync) ------------------- 13 (hsync)
12 (vsync) ------------------ 14 (vsync)

                          /-- 5 (ttl ground)
                         /--- 6 (red ground)
13 (ground) ------------+---- 7 (green ground)
                         \ -- 8 (blue ground)
                          \-- 10 (sync ground)

The mono cable doesn't use the ST's RGB pins, using the ST's mono out instead. Connecting the 'mono detect' pin tells the ST to switch to Mono mode, rebooting if necessary.

Mono Monitor Cable
==================

Atari ST                      SVGA DB-15
~~~~~~~~                      ~~~~~~~~~~ 
                          /-- 1 (red)
11 (mono out) ---[100Ω]--+--- 2 (green)
                          \-- 3 (blue)

9 (hsync) ------------------- 13 (hsync)
12 (vsync) ------------------ 14 (vsync)

                          /-- 5 (ttl ground)
4 (mono detect) ----.    /--- 6 (red ground)
13 (ground) --------+---+---- 7 (green ground)
                         \ -- 8 (blue ground)
                          \-- 10 (sync ground)

So it would be pretty simple to make one of those cables, or make both and just plug and unplug them to switch from colour to mono, but it is more convenient to add a switch.

 

I'm using a bog-standard 4 Pole 2 Throw 2-position switch. Electrically speaking this is 4 separate switches (poles), each of which has a common pin that is connected to one of two other pins (2 throw) depending on the position of the toggle lever. Here's a photo of one of these switches, I've numbered the separate swtiches 1-4, labeled the common pins C for each switch, and called the two positions A and B. When the toggle in in position A, 1C is connected to 1A, 1B is not connected, 2C is connected to 2A, etc. Note that position 'A' is up in the diagram, but the A pins are on the bottom- might be confusing when you wire it up and label it if you don't notice that.

 

post-39360-0-72651300-1413413309_thumb.png

 

So I use the switch to create a single cable that can behave as if it were either of the the above two cables, by wiring it up like this. Pin-numbering on the switch is my own, just to match with the picture above.

Mono-Colour Switched Cable 
==========================

Atari ST                      4PDT Switch           SVGA DB-15
~~~~~~~~                      ~~~~~~~~~~~           ~~~~~~~~~~ 
4 (mono detect) ------------- 1B       1C --------- ground

                          /-- 2B       2C --------- 1 (red)
11 (mono out) ---[100Ω]--+--- 3B       3C --------- 2 (green)
                          \-- 4B       4C --------- 3 (blue)

           (not connected) -- 1A
7 (red) ---------[50Ω]------- 2A       
6 (green) -------[50Ω]------- 3A
10 (blue) -------[50Ω]------- 4A

9 (hsync) ----------------------------------------- 13 (hsync)
12 (vsync) ---------------------------------------- 14 (vsync)
                                              /---- 5 (ttl ground)
                                             /----- 6 (red ground)
13 (ground) --------------------------------+------ 7 (green ground)
                                             \ ---- 8 (blue ground)
                                              \---- 10 (sync ground)

I bought a whole bunch of these switches a while ago really cheaply on AliExpress. On Digikey or similar you need a switch with Circuit: 4PDT, Switch Function: On-On, like one of these M2042SS1W01:

http://www.digikey.ca/product-detail/en/M2042SS1W01/360-1874-ND/1006952

http://www.newark.com/nkk-switches/m2042ss1w01/switch-toggle-4pdt-6a-125vac/dp/10X8538

Edited by galax

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