MacTester57's HemiMac G4

[kiwisincebirth]

The answer is simple but annoying. The iMac G4 LDC is not able to show more than 262144 colours...

You had me worried about my own build checked out the specs of the 20" G5 panel.

Supported color scales are native 8bit level (8-bit per subpixels data driver).

I'm wondering now, which better LCD would fit into the iMac. Maybe' it's time for a Haswell based HemiMac 2.0!

MacTester

Cool.

 

[MacTester57]

You had me worried about my own build checked out the specs of the 20" G5 panel.

Sorry!

Cool.

If it will happen, then not today and not tomorrow...

MacTester

 

[imarco88]

Hi,
first, congratulation for your iMac G4 mod. Really professional. Impressive.
As you, I was reading dremeljunkie blog for iMac G4 mod, and decided to transform mine into an external monitor. All worked great, but as soon as I closed the dome I was doubting about the PSU and LCD-Inverter Voltage. Then I found this site, and your mod. I immediately registered.

My questions are:
Does the DVI pin 14 VEDID cable give 3.3V or 5V?
where did you hook up the LCD on/off switch cable (pin 15)? To the DVI VEDID pin 14 (as dremeljunkie said) or directly to the PSU 3.3V?
where did you hook up the Red Inverter wire (On/Off) which requires 5V?

Thank you, and again, congratulations

 

[MacTester57]

Hi Imarco88

Welcome to the community

Hi,
first, congratulation for your iMac G4 mod. Really professional. Impressive.

Thanks!

Does the DVI pin 14 VEDID cable give 3.3V or 5V?

The DVI standard says 5V

where did you hook up the LCD on/off switch cable (pin 15)? To the DVI VEDID pin 14 (as dremeljunkie said) or directly to the PSU 3.3V?

It's directly connected to DVI Pin 14. However, I've seen in the meantime in the display data sheet, that it should be connected to 3.3V... Hmmmm... There should be a voltage divider... BUT, it works perfectly. The question is: how long?? -> Rewired now! see http://www.tonymacx86.com/imac-mods/104625-mactester57s-hemimac-g4-19.html#post776973

This is the VEDID / HOTPLUG splice. The green wire comes from DVI Pin 14 and goes to:
-The red inverter cable
-LCD VEDID Rewired to 3.3V!: http://www.tonymacx86.com/imac-mods/104625-mactester57s-hemimac-g4-19.html#post776973
-Via a 1kOhm resistor back to DVI Pin 16

where did you hook up the Red Inverter wire (On/Off) which requires 5V?

It's connected to DVI Pin 14, too:

It is important, that you connect the three LCD power supply wires (LCD Pin 22 - 24) to 3.3V instead of 5V (as dremeljunkie says)

MacTester

 

[imarco88]

The DVI standard says 5V

So I assume these 5V comes from my DVI source (in my case a macbook pro)

It's directly connected to DVI Pin 14. However, I've seen in the meantime in the display data sheet, that it should be connected to 3.3V... Hmmmm... There should be a voltage divider... BUT, it works perfectly. The question is: how long??

That's the main point
I believe that the display was done to be always on, like a laptop display. So I presume that LCD pin 15 should be hooked with the other LCD power supply wires (Pin 22 - 24) to 3.3V, and then move the inverter red cable, that now

It's connected to DVI Pin 14

to a 5V from the PSU.

It is important, that you connect the three LCD power supply wires (LCD Pin 22 - 24) to 3.3V instead of 5V (as dremeljunkie says)

Yes, thank you for investigating the inverter connector.
Is it also important to connect the Orange wire to 3.3V and the Green wire + 1 kohm resistor to 3.3V (instead of 5V (as dremeljunkie says)?

 

[MacTester57]

So I assume these 5V comes from my DVI source (in my case a macbook pro)

Yes

So I presume that LCD pin 15 should be hooked with the other LCD power supply wires (Pin 22 - 24) to 3.3V

Yes, try that

and then move the inverter red cable, that now is connected to DVI Pin 14 to a 5V from the PSU.

No, you can wire it to DVI Pin 14

Is it also important to connect the Orange wire to 3.3V

Yes, if you want an adjustable CCFL brightness and therefore put an adjustable voltage to the green inverter wire

and the Green wire + 1 kohm resistor to 3.3V (instead of 5V (as dremeljunkie says)?

For the green inverter wire refer to the table above. There are two possibilities:
-a potentiometer
-a PWM signal from a microcontroller

Good luck

MacTester

 

[ersterhernd]

Hmmm, do you think we should be pulling these iMacs apart and rewiring the VEDID to 3.3V MacTester?

I've been wondering about this...


Ersterhernd

 

[MacTester57]

Hmmm, do you think we should be pulling these iMacs apart and rewiring the VEDID to 3.3V MacTester?

I've been wondering about this...


Ersterhernd

I've realized this issue after you've talked about your 17" G5 panel... They all are built for a 3.3V VEDID signal.

I think, that I will not change the wiring - No risk, no fun!

Your thoughts?

MacTester

 

[ersterhernd]

I love taking risks, but how much risk exists here? I know it'd be a pain in the butt to rip into all that wiring again in the G4's. I think I'll try to implenent it in my G5 build though.

I just read about my 20" iMac panel, it specifies either 3.3 or 5.0 volts vedid in the tech spec. The two panels are quite different though, so I found out.



Cheers!

 

[imarco88]

No, you can wire it to DVI Pin 14

I thought to plug the red inverter wire to the 5V PSU just because the LCD won't be anymore VEDID-dependent (since I'm gonna plug pin 15 into PSU 3.3V), I don't see why the inverter should be . Anyway, PSU or VEDID, both are 5V, I think it's just a matter of Amperage.
Since I'm not interested in variable brightness at the moment, I'll leave the Orange wire unplugged.

one more, and hope last, doubt: why is the DVI hot plug wired to the VEDID with a resistor? Dremeljunkie says that hot plug is at low voltage (sure lower than VEDID 5V, because this goes to the DVI source), isn't it better to wire it at the 3.3V PSU?

Good luck

Thank you, I'll update when I will complete the mod.