Mac To Vga Sync On Green

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Mac To Vga Sync On Green

Does anyone know if the video pin 8 on the sync on green macs like the IIci etc is a 12 volt voltage source.

Most pinouts just have a no connection or reserved for pin 8.

I'll be measuring my IIci soon but if anyone knows about the mysterious pin 8 on the other sync on greem macs please reply.

If Pin 8 is a voltage source then you can build a simple circuit using
the LM1881 sync seperator and power it with the voltage from pin 8 and it will let you use the sync on green macs with any vga monitor instead of buying the griffin adapter.

The circuit is here.

http://193.23.168.87/Apple_Mac/IIci-VGA/MacIIci_VGA_Monitoranschlu.html

It's not in english but basically the circuit seperates the sync signals from the green video and then the seperate sync signals can drive any vga monitor.

You can power the LM1881 chip with the floppy voltages or external power or maybe with pin 8 from the video plug which is what I'm trying to find info on.

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Google

Google translator works

http://google.com/translate?u=http%3A%2F%2F193.23.168.87%2FApple_Mac%2FIIci-VGA%2FMacIIci_VGA_Monitoranschlu.html&langpair=de%7Cen&hl=en&ie=UTF8

I think I'm going to try this with my IIsi, as it has the same problem, and the only monitor I have that works with it is a HUGE mitsubishi.

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I measured pin 8 on the m

I measured pin 8 on the mac IIci video plug and there was no voltage on it so the circuit needs to be powered from the external floppy connector just like the article says.

I've checked the external floppy power pinouts from the circuit diagram with the IIsi apple docs and they are ok for the +5 volts and ground.

There are a few things that are probably misprints in the
circuit diagram.

On the standard vga side for the grounded pins, pin 5 should be changed to pin 6 (vga red ground).

Pin 5 on a vga pinout is a no connection.

And on the Mac II side for the grounded pins, pin 13 (Mac Blue Ground) should also be grounded.

btw it's not really sync on green as the composite sync is not included with the green video signal but is on the seperate csync pin.

The IIci or IIsi output the composite sync on the csync pin and the green video has no composite sync included with it so the green signal is just like the blue video and red video signals.

Interestingly in portrait monitor mode the IIci and IIsi output seperate hsync and vsync and no composite sync.

I got all this composite sync stuff from the IIci IIsi apple docs.

If you really want to be exact you could include a couple of logic gates that give a better hsync output but it's not really needed.

http://www.hut.fi/Misc/Electronics/faq/vga2rgb/scart.html

The capacitors used in the circuit should be ceramic types not
electrolytes.

Also you could change the capacitor and resistor values if the circuit doesn't work as expected.

See http://partsandkits.com/LM1881.pdf

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new chip

You can connect pin 5 on the vga side to ground as well as the others but it's not essential in fact I've got a vga monitor that has no pin 5 pin on its video plug.

You can also use the EL4583 chip instead of the LM1881.

The EL4583 chip gives a better hsync than the LM1881 that works with more vga monitors and costs a bit more but not
much more.

The pinouts are different though but if you compare it to the
circuit diagram it uses the same parts as the LM1881 circuit
but the pin numbering is different.

For the EL4583 chip

http://www.intersil.com/data/fn/fn7173.pdf

Pin 3 CSync out

Pin 5 VSync out

Pin 6 ground

Pin 8 CSync in with the 10nf capacitor.

Pin 12 390k resistor and 10nf capacitor in parallel then connected to ground.

Pin 14 is +5 volts

Pin 15 is HSync Out

All the other pins are left unconnected.

Both the LM1881 and EL4583 are available from RS Components.

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New chip errata

Forgot a ground pin.

Pin 16 on the EL4583 chip should also be grounded as well as pin 6.

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power

At
http://www.griffintechnology.com/archive/video/macsyncii.html

the macII vga adapter uses an active circuit (like the LM1881 circuit above) as they put it
meaning it needs a supply voltage but their adapter needs no external power supply
so they must be getting the supply voltage from the MacII video plug.

I measured pin 8 on my Mac IIci and there is no voltage on that pin but all the sense pins (0, 1, 2) and the sync pins (csync vsync hsync) have roughly 5 volts on them.

Seeing that the hsync and vsync pins are unused (only the csync pin is used) for the LM1881 circuit above you
could try powering the LM1881 IC by using the 5 volts on the vsync or hsync pins
so you don't have to use the 5 volt supply from the macII external floppy connector as the LM1881 circuit above does.

The LM1881 IC doesn't draw much current from the power supply.

This or something similar is probably what griffin are doing with their adapter.

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sog

Earlier I said that the composite sync is on the mac csync pin and
not included with the green video well it turns out the composite sync
is on both the csync pin and included with the green video signal (SOG)
so you could get the separate hsync and vsync signals by using either
the csync or the green video as input to the LM1881 chip.

In the LM1881 circuit the csync pin is used.

MacII and vga pinouts

http://developer.apple.com/technotes/hw/hw_08.html

http://www.monitorworld.com/faq_pages/q17_page.html

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Simple MacII to VGA

A lot of VGA monitors can't accept the
composite sync when it's mixed in with the
green video signal (sync on green)
but lot of VGA monitors can accept separate composite sync
when it's connected to the VGA monitors horizontal
sync pin.

This is how one of the Mac VGA 10 dip switch adapters
do it.

The MacII's CSYNC (MacII pin 3) is connected to the
VGA monitors HSYNC (VGA pin 13).

Sense Pin 0 (MacII Pin 4) is grounded to simulate
a 13 inch RGB monitor the other MacII sense pins
7 and 10 are not connected (NC).

MacII VGA
1 6 Red Gnd
2 1 Red Video
3 13 Composite Sync (CSYNC)
4 10 Sense Pin 0 connected to Composite Sync Gnd
5 2 Green Video
6 7 Green Gnd
7 NC
8 NC
9 3 Blue Video
10 NC
11 10 Composite Sync Gnd
12 NC
13 8 Blue Gnd
14 NC
15 NC

VGA pinout male
http://www.monitorworld.com/faq_pages/q17_page.html

MacII pinout male
http://developer.apple.com/technotes/hw/hw_08.html

VGA pinout female
http://www.monitorworld.com/Cables/video_standards.html

All pinouts are looking at the front of the plug.

Needs a male DB15 plug and a female HD15 plug.

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pinout numbers again

MacII VGA
1, 6 Red Gnd
2, 1 Red Video
3, 13 Composite Sync (CSYNC)
4, 10 Sense Pin 0 connected to Composite Sync Gnd
5, 2 Green Video
6, 7 Green Gnd
7, NC
8, NC
9, 3 Blue Video
10, NC
11, 10 Composite Sync Gnd
12, NC
13, 8 Blue Gnd
14, NC
15, NC

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Use a Mac Monitor on a PC

To use a PC on a Mac Monitor like the Apple
Multiple Scan 15av.

VGA Mac
1, 2 Red Video
2, 5 Green Video
3, 9 Blue Video
4, NC
5, NC
6, 1 Red Gnd
7, 6 Green Gnd
8, 13 Blue Gnd
9, NC
10, 14 Sync Gnd
11, NC
12, NC
13, 15 Hsync
14, 12 Vsync
15, NC

Mac DB15 pinout female
http://www.monitorworld.com/Cables/video_standards.html

VGA pinout male
http://www.monitorworld.com/faq_pages/q17_page.html

All pinouts are looking at the front of the plug.

Needs a female Mac DB15 plug and a male VGA HD15 plug.

Tested with no problems using a nvidia TNT card and a Apple
Multiple Scan 15av

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composite sync and green to SOG

If you want to make a sync on green signal from
seperate composite sync and green video signals

check out

http://www.electro-tech-online.com/viewtopic.php?start=0&t=8657

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Simple MacII to VGA test

I tested the Simple MacII to VGA
with a Mac IIci and an old MAG Innovision SVGA monitor
and it all works great.

Obviously the MAG Innovision SVGA monitor
can handle the composite sync from the Mac IIci
fed into the monitors horizontal sync input but some
vga monitors won't be able to do this but a lot will.

Interestingly the MAG Innovision SVGA monitor
can't handle sync on green (composite sync mixed with green video) coming from the Mac IIci.

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Self Power for LM1881

Earlier on in this thread I was wondering how Griffin
could use active components like IC or transistors
for their mac video adapter and not require any external power supply to power the IC or transistors.

The Griffin adapter is self powered but there is no pin that supplies
a voltage to tap into from the Macs video port.

I guessed the Mac Video pin 8 might have a usable voltage supply but it doesn't.

I mentioned maybe using the Mac Video Hsync Pin because
I measured it to be about 5 volts.

Well here is a possible answer

http://www.arcadecollecting.com/info/Combine_and_invert_syncs.txt

with the relevant bit being

take two diodes, tie them to H and V
sync, add a 20uF capacitor, and use it to power
the CMOS inverter. (ie LM1881 IC).

This apparantly was used to self power an Apple Midi Interface.

This small circuit could have a lot of different uses.

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Self Power pdf circuit diagram

Here is the Self Power circuit diagram.

It's pretty simple

http://www.mikesarcade.com/wiretap/info/SyncInv.pdf

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Mac II self power

For the MacII 5 volt self power supply to power the LM1881 chip
change (from the pdf above) the 2 diodes connected to the separate vsync
and hsync pins to 1 diode connected to the MacII's csync pin.

For a LC which has separate v & h sync you would just use
it how it is in the pdf.

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More Info

Tested the self power using the csync signal and it works
great.

I'm able to get a steady +5 volts from the csync signal to power
a chip.

The LM1881 chip outputs separate vertical sync and composite
sync and not horizontal sync.

Most monitors can handle using the LM1881 composite sync output for the horizontal sync but some monitors require
real horizontal sync like my Multiple Scan 15AV Display.

All you need to get real horizontal sync from the LM1881
composite sync output is an invertor and a nand gate.

To make an invertor from a nand gate just connect the
two nand gate inputs together and use it as the input.

LM1881 Pin 1 (composite sync out) goes to the invertor then the output of the invertor goes to one input of the nand gate.

LM1881 Pin 3 (vertical sync out) goes to the other input of the nand gate.

The output of the nand gate is now just horizontal sync
which works with my fussy Multiple Scan 15AV Display .

I used a 74hc00 cmos nand chip for the invertor and nand gate.

You could also use a 74ls00 nand chip as well.

The info about deriving horizontal sync from the LM1881 at

http://www.hut.fi/Misc/Electronics/faq/vga2rgb/scart.html

appears to me to be wrong.

If you do it using a nand gate and a and gate you get no signal at all
coming out.

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