monitor SILICON GRAPHICS - Adaptation for PC
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I want to thanks Sylvain Grosjean, electronic teacher for all the time
and the assistance that he brought to me, and Julien Leduc for the technical
I thank also Adam Kropelin ( http://www.kroptech.com/gdm20d11mod
) who have give me the right to re-use his photograpy of the back of
It is sometimes very interesting to re-use old monitors of workstation
for our PC computers, but it could be difficult to adapt these monitors to
use them on PC because their operating mode is often different. I present
here the adaptation i had made and which function for my monitor SONY GDM
20D11 to use it on my PC. Of course, you can reproduce this solution at your
own risks, I decline any responsibility for the damages that that could cause
the use of the informations you can find in this page.
CAUTION: OPENING A MONITOR CAN EXPOSE TO VERY HIGH VOLTAGE (UP TO 25
000 V WHEN THE MONITOR IS UNDER FUNCTION, AND UP TO 300 V WHEN UNPLUGGED IN
SOME CAPACITORS). IT'S ENOUGH TO KILL SOMEONE.
DO NOT TOUCH ELECTRONICS ON A MONITOR UNDER WORKS. UNPLUGGED IT BEFORE
AND DISCHARGE THE CAPACITORS
A part of the monitor, in the switching power supply, is connected
to 220 V (or 120 V for country in 120 V)
A part of the monitor is under very high voltage (up to 25 000 V)
Even disconnected, some capacitor can remain charged under high tension
(300 V rather classically). Attention with the discharges.
Consult the security page of the site http://www.repairfaq.org
Presentation of the issue
The monitor SONY GDM20D11 is a fixed frequencies monitor whose frequencies
of synchronization are higher than the frequencies used for VGA
(31,5 Khz in horizontal frequency, 60 vertical Hz) we can use it under X11
or windows with the right resolution and the right frequencies. However VGA
mode is used to start the PC (bios tests) and the operating system (text mode
starting for linux, starting windows for windows). It is also used
for the "safe mode" of windows. This monitor synchronize from 48 to 82 Khz
horizontally and near 70 Hz vertically. You can use it between 1024x768 70
Hz to 1280x1024 70 Hz (it could also be used in 1600x1200, but some pixels
According to http://hawks.ha.md.us/hardware/monitors.html
the monitor has the following characteristics:
* this does not prevent from displaying higher resolutions (it is most
surely the case on your monitor in this moment)
freq hrz (Khz)
freq green (Hz)
physical resolution max *
The tube is a " black trinitron ", which means that this monitor does
not display a distorsion along the vertical axis (the surface of the monitor
is cylindrical and not " spherical " as on the majority of the monitors).
The second problem (and it is not the least), for a user of PC, is that
this monitor uses only three input signals: a red, a blue, and a green signal,
the green signal containing the signals of synchronization. Even if the connector
is a 13W3 (presented further) containing 3 connectors for the colors and
10 pins annex for the others informations, in fact, only the three colours
connectors are connected to another thing than the ground or nothing.
Connector HD-15 (side PC)
||VGA - VESA (principal functions, communication for the nondetailed
||BIT ID or reserved
||no pin or + 5 V (generally the PC provides +5 V on this pin which
can be used to supply power to an external circuitry such as a logical gate
used to combine H sync signal and Vsync signal).
||BID ID 0
||BIT ID or SDA: DDC serial line data (for PNP monitors)
||horizontal synchronization (on certain graphics boards composite
||not connected or SCL: DDC clock line (for PNP monitors)
Connector 13W3 (monitor side)
For the monitor which interests us the pin A1 (center) is connected to
the red, the pin A2 with the vert+sync, the pin A3 with blue. Pins 2 to 5
are, in the monitor, " in the air ", the others are connected to the mass.
For other monitors, following interfacings are possible (source: http://www.monitorworld.com )
Note: the connectors A1, A2 and A3 are armoured and the shielding is always
connected to the analog mass.
||IBM Power PC
||id bit 3
||+ 12 V
||id bit 2
||id bit 0
||power switch cont
||id bit 3
||monitor sensing 2
||id bit 2
||- 12 V
||id bit 0
||id bit 1
||id bit 1
||monitor sensing 1
||sync 2 (obsolete)
||composite sync GND
||composite sync GND
Solutions which not
require a modification of the monitor (to be avoided only use to test if
monitor is good)
You can find some solutions, using resistors and/or of logical gates.
Refer to the " sync one green FAQ " on http://www.repairfaq.org
These solutions consist in generating a sync on green signal as clean as
possible, which is then transmitted to the monitor. Resistor based solutions
are not particularly " clean ", Logical gates based solutions and transisor
or FET solutions are complicated electronics, requires an external supply
voltage and can be dangerous for the monitor in some cases.
Solution for all graphic cards which accept to generate 1024x768
70 Hz minimum
A solution can be used to generate "sync on green" from Hsync, Vsync
and Green signal, by adding all these signals in one, using resistors. This
solution works with some problems : If the resistors are too high, the sync
signals are not high enough and the monitor doesn't synchronize. If the resistor
are too low, the green signal is disturbed and the display is a bad quality
This solution can be used to test if the monitor is working correctly,
The value of R is to be determined. Start with resistors near 10 K Ohm,
and decrease slowly. The good value is depending on the graphic card. A 100
Ohm value works perfectly with GDM-20D10, but connected to the pin 5, not
to the A2 one.
Note: I had tested this solution, it is not the best. it involves
a strong attenuation of the green signal, and the image is not correct any
more in term of colors (that depends on your graphics board, but in all the
cases it is not very good.) i propose only to use it in order to test the
Opening the monitor
The schematic of the solution i had used is presented on
pictures re-used frome the Adam Kropelin website. Adam Kropelin had done
a good modification to GDM-20D11 to make it works on SUN Worstations. On his website you will find
the good methodology to open the monitor properly
the URL est this one : http://www.kroptech.com/gdm20d11mod
on the back of this protection is the pcb to be modified.
The good cable
for the proposed solution
All the modifications i'm going to propose to you is based on this
cable. the red signal (pin one) on HD-15 is connected to red (A1), the green
to green (pin 2 to pin A2), the blue is connected to blue (pin 3 to pin A3),
all the ground to ground (5,6,7,8,10 to A1 ground, A2 ground, A3 ground),...)
the hsync signal (pin 13) to the pin 5 and the vsync signal (pin 14) to the
The first solution, works if
you can set the synchro signals to negative on the drivers of your graphic
This is a good solution i have found later than the other, but which
permise to have a very good display and to use the monitor on a PC or on
a SGI workstation It is based on the analysis of the electronic engineering,
and on the results of older try.
Sun has done the circuitry like that (see the picture next) : The red signal
is reported to another electronic card. The blue signal is reported to another
electronic card. The green signal is also reported to another electronic
card, but is put on the enter of an electronic filter made with two resistor
and a capacitor which make what whe called in french a "passe haut". It's
a filter which let the high frequencies goes and which stop the low frequencies
and the continuous signals.
Existing electronics, before modifications. On the picture next you can
see the location of the various components.
I have tried before to add to green signal the Hsync Signal and the Vsync
signal through 100 Ohm resistor. This have for consequencies to perturb the
The idea is, here, to reconstituate the filter with the other passive
components than the one which are on the PCB. Using this solution, the two
perturbating signal are now linked to the green signal with a very high impedance
according to 100 Ohm one.
The schematics is this one : R is linked to pin 1 of HD15, V is
linked to pin 2 of HD-15, B is linked to pin 3 of HD-15, Hsync is linked
to pin 13 of HD-15, Vsync is linked to pin 14 of HD-15 and all signal
are corerctly grounded (ground can be found on pin 6,7,8 and on pin 10 of
In order to use the same cable as presented before (you have to do it
yourself), the modifications are the one presented on the picture next.
The cable you have to do is this one
What you can also do is to buy a HD-15 to 13W3 adaptor, to test it to
see where are connected the HD-15 pin 13 and 14, and to sold the 2,2 K resistor
to the correct pin of the 13W3 on the PCB, after having disconnected it from
the ground if necessary. (it's what i have done).
Now, plug the monitor and do the correct
settings. (you have to do this with a good multisync PC monitor in order
to display something even if it's a bad one settings).
because these monitors are not PC compatible, you cannot display the
bios test and the boot of your favorite OS. So it's necessary to have at
least a 14' monitor which can display VGA mode to do the settings (in "safe
mode" of windows or in console mode of linux).
Some graphic cards are designed to display all mode on fixed frequencies
monitors, but this graphic cards are so expensive that it will be better to
buy a monitor ! The interest of these is that you don't have to modify anything
in the monitor. These graphic cards generate a correct "sync on green".
If you wan't too, see .http://www.si87.com/.There's
another manufacturer i have found, but i have forgotten the link and the name.
The price seems to be quite equal to Si87.
Even if you put a high resolution on windows or linux, there's no chance
that it can works correctly on the first try. In fact, it's necessary to adjust
two or three things:
Because a lot of graphic cards does not have this sort of settings you
will have to download (and to buy if its works correctly) some soft, especially
for windows users (linux one should have more freedom to set the parameters
as they wan't too, see X11 manual).
- a good resolution (1024x768 or 1280x1024 or, why not, 1600x1200)
- a vertical frequencie near 70 Hz
- an horizontal frequencie which can be accepted by the screen
- a vertical polarity and an horizontal polarity correctly setted
(i'm thinking that the settings of Hpol and Vpol is used to "tell" the monitor
which resolution is to used, but i'm not sure. What i knows is that some polarities
works with 1024x768 and does not works in 1280x1024).
Two softs seems to permise this : powerstrip and univbe. I have tried
powerstrip (not the 3rd version but the 2.78 version only), which works correctly
but which start at the end of the windows boot. very good for searching good
parameters. Then i used only the soft of my graphic card (matrox) as you can
As you can see on the picture next, the settings displayed are correct.
But be careful :
The settings you can see next, are used on a PII 333 operating under
windows 2000 professionnal at my works. It replace an old 17'' of bad quality
and is very confortable to use CAD soft such as catia V5. The videocard is
an MATROX AGP G200.
- The polarity of the Hsync and Vsync signals are important to do
it works properly, test different combinations.
- Settings a refresh rate (here 70,023 Hz) is not enough, except for
the lucky people, it's a hasard, to obtain a correct display. You have to
modify the front porch, back porch,...
- If the settings aren't good, the monitor doesn't display anything
(it goes on energy saving mode). To avoid this, you can modify the position
of the switch (put it on "test"on the PCB (the one you have modify before),
to display something, even if there's no synchros. But it modif- also the
works of the remote units (a press on + and you go on the max, a press on
- and you go on the min). It's good to set the correct parameters, but it's
not very practical to use on a daily use. Once the settings are good, put
again the switch on "normal"
- no display in "safe mode of windows". or in text console mode.
So use it only with a relatively stable OS (avoid windows 9x, or meuh, prefer
linux or windows NT (which mean Neanderthal Technology) or 2000. I've no informations
on the stability of XP but a new OS is often unstable, above if microsoft
is the manufacturer.
a modification for
all graphic cards
The whole explanations are given on the french page. my english is too poor
to repeat all these explanation here. i'm using a XOR gate (74HCT86) (the
symbol is a rectangle with "=1" written inside on the french schematics) and
pair of resistance and capacitor in order to transform all sort of synchros
(positive or negative) in negative one. The principle is to generate the mean
of the signals by using filters ("passe bas" in french), and to make
a XOR of the signal and it's own mean. The schematic is this one :
what we want to obtain in all cases
what we can have in entrance(four cases possible):
with R3=R4=2,2KOhm and C=100uF like in the first solutions (the difference
is the use of a gate.
The PCB is this one :(GIF 300 DPI)
The implementation is this one :
The PCB was made with the soft TCI from bruno urbani : http://b.urbani.free.fr (freeware)
Connect the +5V to +5V of the M1 PCB, the GND to the ground, the Hsync to
your hsync (where you have putted it) the vsync to the vsync (idem) and the
G point (GDM-OUT) to the base of the transistor, at the same place the capacitor
is sold in the previous solution.
simply set your monitor to 1024x768 or 1280x1024 at 70
or 72 or 75Hz and it will works correctly. Then, use the remote control or
your graphic card soft to adjust the display on the monitor.
About the GDM-20D10
They accept a composite sync on the pin 5 of the 13W3. So there's
no problems about disturbing the green signal, so it's sufficient to make
a cable with an addition of Hsync and Vsync through 100 Ohm resistor (or more)
connected to the pin 5 of 13W3.
a GDM20D10 have four display mode :
1280x1024 81,1 kHz 76 Hz ;
1152x900 71,8 kHz 77 Hz ;
1280x1024 71,7 kHz 67 Hz ;
1152x900 61,8 kHz 66 Hz;
I suppose that the choice between the different mode are made by the type
of the synchro (negative-negative, negative-positive, positive-negative,
positive-positive) but i don't know
which one is set to which resolution.
For the rest, it's nearly the same monitors than GDM-20D11 and the settings
problem is nearly the same (the correct frequencies can be quite different.
See the manual sold with the monitor .
the doc of the cxa 1616S can be found here : http://repair.vist-v.ru/ds/ic/video/CXA1616.pdf
you can find two principal pages of this manual here :
a modeline to make a gdm20d11 works correctly in 1600x1200 (thank's to
Yann E morin)
Modeline "1600x1200" 162.30 1600 1616 1808 2040 1200 1200 1203
1248 -hsync -vsync
For any informations, you can contact email@example.com, in french
if possible. All question in english should have a reply in a long delay,
and in a poor english (see this page to judge).
Don't forget that, if you want to do some modif on your monitor, it's at
your own risks, I can't be responsible for the use you can do of this page.