Changing the Digital I/O Power-up State of the USB-1208LS and USB-1024LS

By removing the unit from the blue case, and with some skilled de-soldering and re-soldering, any or all ports can be set for pull-down instead of the default pull-up. i.e. if you are handy with solder/desolder equipment for tiny surface mount zero-ohm resistor(s), then the change can be performed in the field. Here are the details:

Note that the USB-1024LS uses the same PCB as the USB-1208LS. For the USB-1208LS, only ports A and B apply, but the USB-1024LS has 3 pull locations (for A, B, and C)

On the side where LED is, locate RN1, RN3, & RN5 resistor packages. You will find the jumpers (zero ohm resistors) between each. By default they are soldered to ‘H’. you can move (the zero ohm jumper) to ‘L’ which will make the respective port pull down (RN1/R69 is for port A, RN3/R70 is for port B, and RN5/R71 is for Port C). In summary, move the zero ohm jumper/resisto, do not move the resistor networks (RNs).

NOTE: If you do not feel you are qualified to accomplish this task, as these 0 Ohm shunts are fabricated using fine pitch components, please locate a qualified solder resource in your area. If you damage the circuit board, the product will likely be damaged beyond repair.