CFA633 Can't turn the system ON


New member
I am trying to POWER ON/OFF the system using CFA633 but this feature is not working. I am using Tyan's S5201 motherboard which doesn't have any WOL header onbaord so I am pulling +5v STBY directly from power supply.
When I hold the power ON button on CFA633, the display on LCD screen comes up for a second displaying CrystalFontz FW version but it doesn't turn on the system. The display goes off after a second or so. I had tried to swap the single wire that has to be connected to motherboard power ON switch. I get above behavior when single wire is connected to POWER ON pin, but if I connect the same wire to GROUND pin and press the power ON button, that turns on the system but the system automatically turn itself off after 4-5 seconds.
Can anybody help me out with this problem ?
BTW, reset function works fine.

Appriciate your help...
Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.

CF Tech

Some background questions:

Did you purchase the ATX cable from us, and on the same order as the 633?

Please look at the lower right corner of the back of the 633, tell me if JP8 and JP9 are closed.

Is the unit USB or serial?

Is the unit "blue" or "yellow".

Do you have the standard "floppy" connector connected to the 633?

Do you have a DMM? Can you use it to verify that (with the standard power switch attached to the motherboard) one of the pins on the motherboard goes low to turn the unit on, and the other pin always stays low?


New member
Yes, I purchased the LCD with ATX power cable from crystalfontz. The header was soldered onto the LCD by crystalfontz.

JP8 is open while JP9 is closed. These are USB LCDs and I have both Yellow and Blue Colors.

A standard floppy connector is connected to CFA633. I had tested the motherboard by connected a power switch directly to power switch pins on the motherboard and that works fine.

I was going through other postings and found some postings where people had mentioned about 'high pulse' reguired by the motherboards. Can you please explain me what it really means ?
USB LCD Displays - Graphic and Character LCDs with a Keypad

CF Tech

Thanks for the background information.

The front-panel switches on a PC case are just contacts--they just short the two pins on the motherboard together.

In my experience, on the vast majority of motherboards, one of the two pins is "Ground" and the other pin is "pulled high" by a resistor. When the two are shorted the one that was pulled high is now forced to ground.

To be compatible with systems like that, the 633 pulls the line low that is not "Ground".

Now there is no reason that a motherboard could notbe designed to have one of the pins set to "high (+5v)" all the time, and the other pin pulled low. Then when the switch is closed the pin would be forced high and the system would power up.

To determine what is going on on your system, I would need you to measure the voltage on the two pins. Once with the switch pressed, and once with it not. That will tell you two things: 1) which pin changes when the switch is pressed and 2) whether the pin then goes high (+5v) or low (ground).


New member
I did a quick test as you told.
When the system is in OFF state (switch is not pressed)
POWER BUTTON pin - +5.07v
GROUND pin - 0v
When the system is in ON state (switch is pressed)
POWER BUTTON pin - +5.14v
GROUND pin - 0.004v

FYI, just to eliminate the possibility of having a bad motherboard, I tried this on two different motherboards of same model i.e. Tyan S5102.


New member
What you want to measure is the voltage on the pins when they are momentarily shorted to turn the unit on or off.

If you are using a mechanical front panel switch, just keep it pressed while taking the measurement. Don't let go until you have measured.

If the voltage drops to zero while the switch is pressed, you know that the motherboard wants a low pulse to turn on or off.