I've trying to get my Viewsonic VP171b to work with my Turbo Color Slab, both of which are sync on green. I'm sure I've had this monitor working with my slab before or it may have been another Viewsonic monitor I have that's 5000 miles away.
I've got a 13w3 adaptor (meant for an SGI 20e21) & F-F gender bender connected to the slab's Y cable but the monitor though it comes out of power save mode (LED goes from orange to green) the screen displays nothing other than black, in fact the monitor stays off as there is no backlight visible round the edges.
AFAIK this should work, I checked continuity using an ohm meter from the following:
13w3 red pin and earth go to svga pins 1 & 6 respectivly
13w3 green pin and earth go to svga pins 2 & 7 respectivly
13w3 blue pin and earth go to svga pin 3 & 8 respectivly
I tried it like that and it does not work, so I started to break out pins on the SVGA side of the 13w3 adaptor in case the H/C sync on pin 13 was grounded or pulled high. I did the same for pin 14 which is V sync, still nothing so I then pulled out every other pin except 1,6,2,7,3,8 and it still does not work.
My question is, Composite Sync on Green means that a combined H/V sync is sent over the pin and earth of Green Co-Axial. What is this supposed to to on the SVGA plug?
Should it be routed to pins 2 & 7 or should it route to pins 13 or 14 and pin 10?
What I mean by this, by defination, when talking about a SOG SVGA monitor, should the SOG signal route to the Sync pins of the SVGA connector and the monitor filters out the Green or should the SOG signal route to the Green pins 2 & 7 of the SVGA connector.
I chose an SGI 13w3 as they are closer so I thought to NeXT (they both use SOG) than Sun, but everybody here seems to be using Sun 13w3 adaptors, which I heard when used on an SGI you had to snap pins out, this has been confirmed to me by a friend who has an Indigo II hooked up to a Mitsubish monitor. Now I'm thinking that as Sun uses C Sync that the Sun adaptor may route the SOG to the H/V or C Sync pins of the SVGA connector. I know that sounds odd but some Sun's output SOG (Creator 3d?), thus maybe people here are using these and not SPARC adaptors?
Otherwise the monitor is working fine using DVI and I know the SVGA wors OK with my MacBook Pro.
iirc I've had this same monitor working on my Octane using a 13w3 adaptor but I'm not sure if thats a Sun or SGI or even a DEC or IBM one. Unfortunaly Octane and 13w3 adaptor for it are 5000 miles away so I can't test it.
Thus if anybody can confirm this, or if they have an ohm meter and an adaptor known to work, if they could tell me if the center pin and ground of the Green (A2 I think) are connected to anything else on the SVGA other than pins 2 & 7 (perhaps pin 13 or 14 and pin 10)
http://pinouts.ru/Video/nextcolor_pinout.shtmlhttp://pinouts.ru/Video/VGA15_pinout.shtmlhttp://pinouts.ru/Video/VGAVesaDdc_pinout.shtmlAFAIK SVGA specifies TTL for C/H/V Sync on pin 13 and 14 but I could be wrong.
Help appriciated as this is driving me nuts.
Hi brams,
I tested my Colorstation adapter (SW3VM) twice with an ohm meter and these are the pinouts on this adapter:
The 13w3 green center pin goes to svga pins 2 and 12. The 13w3 green outer shield goes to svga pin 7.
The 13w3 red center pin goes to svga pins 1 and 11. The 13w3 red outer shield goes to svga pin 6.
The 13w3 blue center pin goes to svga pins 3 and 13. The 13w3 blue outer shield goes to svga pin 8.
Hope this helps.
Cool Nitro, thanks very much for the help and input, I'm even at more of a loss as pins 11 & 12 seem to be either serial data links for DDC/EDIC info or ID Bits for DDC. Pin 13 (composite sync) seems promising however it's connected to Blue so you have SOB (Sync on Blue, which of course is a load of crap).
I did however find this remark eariler on a page which seems to be interesting, and I wonder if this is the answer to my dilemma
"This type of cable is used to connect a SGI, SUN or NeXT workstation monitor to a PC. But be warned, the NeXT version of the cable have a different pinout (the blue and green signals are swapped)"
I got that from this page:
http://ahh.sourceforge.net/Workstation-Monitor-HOWTO/mon2pc.htmlThus if this where true, it would mean that pin 13 (composite sync) on the SVGA would be connected to Green according to the pin checks you did before. I do find this a bit weird though as I've used my 21" NeXT monitor on my SGI Octane & used my SGI Granite monitor on my NeXTcube and so if the Green and Blue where swapped I think it would mess all the colours up
In one of the NeXT hardware guides, it gives pinouts, can anybody confirm or deny that Blue & Green is swapped on a NeXT 13w3?
Thanks
brams
I wish I knew more about it but I'm afraid I'm not up to speed on the details of VGA to RGB interfacing. I do have a link that may be helpful.
http://www.epanorama.net/documents/vga2rgb/interfacing.htmlLet us know what you find out as it would be nice to have the pinouts documented.
Thanks,
I've found another site that says NeXT swap the blue and green co-axial connectors in the DB 13w3 connector.
http://www.monitorworld.com/Cables/video_standards.htmlSeems NeXT & IBM (RS6000) use A1 as Red, A2 as Blue and A3 as Green
Everybody else with the exception of Apple use A1 as Red, A2 as Green and A3 as Blue
And Apple apparently swap the Red & Blue with A1 Blue, A2 Green & A3 Red.
So it would seem that, rather purely by virtue that the B & G is swapped on the NeXT rather than by design a Sun adaptor on a NeXT works as it routes the SOG to the Composite Sync Pin (13).
However I'm sill at a loss why my NeXT 21" works fine on my SGI Octane using an SGI 13w3 cable. logically the blue and green colours should be swapped and the monitor should not sync.
The array of 13w3 options and adptors are confusing, I've seen an Octane 13w3 adaptor this morning that says it does SOG and non SOG for use on normal PC monitor, I wonder if that would work aside from the fact it's the wrong gender.
OK, I've made a little progress, not a lot but I have had a glimpse of a NeXT boot screen on the Viewsonic, however I feel the plot maybe thickening.
I've only just brought the Slab with me, I work abroad and it used to be in the UK, however this trip home as I was not bringing much back with me I put the slab in my suitcase. Thinking it may have been damaged during transit I used a Fluke DMM and measured the frequency of the video signals to try and get an idea if the slab was working, I thought it was as it appeared to respond to hitting the power key and pressing Y to shut it down.
R=0Hz
G=100Hz
B=0Hz
No idea if the values are correct hower using a DMM it shows that some kind of frequncy if coming down Green.
I ripped apart the useless (or so I thought) SGI 13w3 adaptor and used it's 13w3 connector. I then used the following parts:
2x 0.1µF Ceramic Capacitors
1x 680kΩ resistor
1x Y cable Molex with case fan fly lead
1x NatSemi LM 1881 IC (sync seperator)
I used the reference circuit contained within the datasheet for the IC
http://www.national.com/pf/LM/LM1881.htmlI also used a few docs I'd seen for using a PlayStation II and XBOX with SVGA montors as both of these consoles output something akin to a composite syn on green. Basically the IC strips the video components of the SOG and seperates the C sync into H & V sync. Thus it allows machines that output a Sync on Green signal to work with an SVGA that supports C sync, H sync or V sync.
After constucting the little circuit and powering it from the slab using the Molex I found I still had no sync, I then removed the V Sync from pin 14 of the SVGA (I disconnected the wire on the LM1881), still the same so I reconnected pin 14 and disconnected H/C Sync from pin 13, still the same, so I then disconnected pin 13 & 14 from V & H/C sync on the IC, twisted them together, and then touched them to the C Sync output of the IC, still the same, green LED (out of powersave mode), no blacklight, nothing at all on the screen. I then touched them both against the V Sync leg on the IC and the backlight came on, the screen remained black but an on screen message appeared saying that the Sync rate was out of range. I then disconnected the wires from the V Sync leg of the IC and I got the NeXT boot screen displayed on the monitor (HD not connected so it just hangs there), for about half a second. I can repeat this at will, if I touch both wires to the leg of the IC, I get the message and when I pull them off the monitor syncs for a split second and then goes black again.
So WTF is going on I ask myself.
It seems apparent to me that, this monitor does indeed Sync to the Green signal, it just does not try hard enough, it tries a bit harder when the V & H/C Sync pins are both connected the the V Sync pin of the LM1881 then it displays the message and makes an effort to sync.
The out of sync range message it gave me was:
H freq: 62Hz
V freq: 3000Hz (after reading the timing specs for the SVGA std, it seems this might be 30khz)
Or the values could have been swapped, I know the values are correct but the H & V may be mixed up.
I have one another couple of observations and this may be the revealing one.
I have a NeXTcube Turbo in the UK, I've used this with this Viewsonic or another one very much like it, I've also used the same TFT on my SGI Octane. I'm also pretty sure I've used one if these TFT's on the slab, again not sure but I know I've used a TFT on a NeXT machine.
I've got a set of ADB KB, SB & Mouse and one set of non-ADB KB, SB & Mouse, I've got 1 ADB Y cable. I hate the ADB stuff and I usually use the non-ADB.
Thus I suspect that when I've used a TFT with the cube or the slab, I might have been using the non-ADB KB etc. iirc plugging ADB gear into a Turbo slab alters the sync freq.
So I'm left wondering if my problem boils down to the fact that I'm using ADB gear on the slab at the moment. This seems to be more or less supported by the fact the other people here as far as I can tell appear to be using non-ADB gear on the TFT systems they are using.
In looking around the net I have discovered that a lot of Multi Sync monitor are not truly such, they are in fact Multi Sync VGA/SVGA/VESA in that they'll sync to these common screens sizes/scan rates, but not guaranteed to work at anything in between. Thus not all Multi Syncs are not created equally. However that said, there where pics on the old forum at www.openstep.se of somebody using a VP171b with a NeXTstation
Does anybody have a TFT set up NeXTstation Turbo Color with both lots of KB's (ADB & non-ADB). AFAIK, it only really applies to slabs as dimensions put out 68Hz even on ADB, which again maybe the reason why I think the dammed screen works on the cube.
Also, the stuff I've seen that says the Blue and Green are swapped, seems to be a load of bollocks are far as I can tell.
Thanks
brams
OK, after reading the docs for the IC, it seems that certain parameters of the V sync signal can be altered be playing about with the resistance of the Rset resistor which is currently set at 680kΩ. It seems this may be a little low or just on the border at 64µs for the vertical sync delay, thus i'm going to try and increase it. To this end I'm gonna try and get a 1MΩ trim pot and use that instead of the resisitor and play with it on the fly to see if I can get the monitor to sync.
OK I got a 0 - 2MΩ PCB trim pot so the experiment will continue tonight.
OK none of this worked, so I give up. I measured the frequncy coming out of the V sync pin of the LM1881 IC and it was 72Hz exactly, I also measured the H sync frequency and it also was 72Hz which I found quite odd as it should have been about 30KHz. 72Hz from the V sync seems to be right for ADB NeXTstations so quite why this is happening I have no idea.
I borrowed the ViewSonic PJ500 DLP projector from work, that works fine with my slab with Sync on Green. I also used it to check the sync seperator circuit I made by turning off SOG on the DLP and it worked fine using the H sync output from the LM1881.
Total cost to build this little thing was about 4 dollars, the IC and capacitor and trim pot/resistor are small enough to fit inside the DB 13w3 shell, worth remebering if anybody wants to try and use a PC screen with a NeXT (albeit not a Viewsonic VP171).
brams