633 USB power supply


New member
Can anyone help me?

I have bouht two 633 with USB interface. I want to install them outside the PC tower, so I would like to feed them trough USB. In other words, I don't wan't to send an adittional power supply cable from the PC to the LCD, only the USB cable WRUSBY03.
Is it possible to do this?
Will the backlights work?
Must I change any jumper on the 633?
Must I do any change over the PCB of the 633?

If it isn't, Can I connect an external power supply to the LCD? Any problem with different GND from the USB interface and from the external supply?

Thanks a lot and sorry for my English.
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New member


The, I'm afraid there is a problem with the LCD or with the installation. I'll explain you the installation process I have done in order that you can help me.

I connected the 633 USB to my computer trough WRYSB03 only, with no power supply power. After that I installed succesfully the USB drivers. Theoretically everithing was OK but I could´t talk to 633 trough Crystalcontrol or Wintest. The LCD seemed OFF because no backlight was ON.

Then I connected a 3_1/2 inch floppy powerr supply able to the "PWR" connector of the 633 (next to FAN2 connector over the PCB) and everything was ON: the LCD backlight, the buttons... and I could talk to 633 without problems using Wintest and CrystalControl.

Do you know where the problem is?

Lastly, I tell you that for my project no additional connections are neccesary: I don´t want to connect any FAN of ATX power supply control. I only want the 633 USB LCD as a remote console with its LCD and its six buttons.

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CF Support

The 633 requires the floppy drive power connection to supply the power for the backlight and logic by default. The USB is only for the serial communication.


New member
Really, so the LCd is not powered by the USB power. Why is that? I was hoping to find a cheaper alternative to the MO LCds, but their USB LCDs can take the power from the usb line.

Is there an easier way to, perhaps, take the Blue/White/Gray 633USB and Buy/Construct a custom cable that would supply the USB and Power feed, so as to create External LCD shells?

CF Support

I think you'll find that any USB LCD that controls fans will require a separate +12v supply. The USB can only supply 500mA at 5v, which is not enough to drive most fans.

The CFA-632 and CFA-634, as well as the CFA-631 can run using only the power from your USB port, so if that's the way that you want to go, there are 3 options.

I imagine there are enough conductors in CAT5, but you'd have to be concerned with whether or not it's "safe" to run +12v through the CAT5 cable for your backlight and fans. The CFA-633 can be set up to power the *logic* through the USB, as that +5v supply is more than ample for the logic itself, but not for the backlighting + fans, etc.

I'm sure there's a way to create a custom cable to run power and everything to the CFA-633, but the main question is having the conductors in the cable adequate to the task.


New member
Well, my primary needs are the Backlight and Logic. If you're saying both of those need more than a 5v line.. Hmm..

I'll look at the other ones. Thanks!

Edit: YGPM. :)

Looking at the 631, is it possible to buy the 631 W/Buttons, W/O Frame, just wanting the LCD itself? It looks like almost exactly what i'm wanting... It just has a useless aluminum frame. :)

CF Tech

Some more detail

The CFA-633 yellow can be strapped to operate from +5v only, powered by the USB.

This configuration is not a standard product but it is possible. We have to change the LED dropping resistors, so there is usually a slight additional cost involved.

By default, the logic is powered from the +5v floppy connector, and the backlight (yellow and blue) are powered from the +12v floppy connector.

The CFA-633 blue does need the +12v for backlight, but can operate its logic from the USB with special strapping.
USB LCD Displays - Graphic and Character LCDs with a Keypad