Digitech RP250 expression pedal repair!

So, the expression pedal of your Digitech RP250 is not working... What could be wrong? Before you start searching for a new RP pedal-board, read this simple guide on how to fix the non-working expression pedal of your rp250/255/350 pedal-board 99% of the times.
The digitech RP-series multieffects have a built-in calibration procedure for the expression/whammy pedal. Whenever the effects gets a firmware update, a factory reset or its CPU encounters an error for some reason (could be a power supply fail, overheat etc), the expression pedal has to be recalibrated in order to work. Sometimes, dust accumulation under the pedal can lead to improper function as well. The trick here is to ensure the PCB is intact and free of dust/humidity.





I opened up the rp250 and checked the ribbon cable that connects the main PCB to the optical expression pedal sensor. I removed the expression pedal pcb and cleaned the optican sensor with some contact cleaner and a piece of cloth. Some solder joints of the optical sensor chip looked a bit tired so I did a solder reflow with plenty of fresh flux. Also, the main pcb was removed after I pulled all the knobs off. The pcb and all its jacks were sprayed with contact cleaner and the up/down plastic buttons were tightened up a bit (there are two metal springy clamps that hold the two buttons in place). The pedal could still not work but these steps were carried out to ensure the reset does not happen again for no reason. Then, the expression pedal was calibrated using the following guide of the operation manual:

"Expression Pedal Calibration
The Expression Pedal on the RP350 needs to be recalibrated for use after a factory reset has been performed. This calibration procedure is automatically entered after a factory reset procedure.
(You can also initiate the calibration procedure by pressing and holding both Footswitches
for approximately 5 seconds.) In the event the Pedal’s calibration fails, or if the Pedal does not function properly, it can be re-calibrated using the Pedal Calibration procedure. This will not erase the User presets. The procedure for Calibrating the Expression Pedal is as follows:
. Press and hold the Up/Down Footswitches until PDLCAL appears in the display (BYPASS, TUNER, and Exit will be displayed before PDLCAL is accessed, after about 5 seconds.)
2. When the Display prompts you with TOE DN, rock the Expression Pedal forward (toe down) and press either Footswitch.
3. When the Display prompts you with UP, rock the Expression Pedal back (toe up) and press either Footswitch.
4. The Display now prompts you to calibrate the V-Switch sensitivity (VSwxxx), where XXX is the current V-Switch threshold. Rock the Expression Pedal forward and press firmly on the toe once to turn the V-Switch on (wah ON), and again to turn the V-Switch off (wahOFF).
5. If the V-Switch is too sensitive, press the right Up Footswitch to raise the threshold (range is 0-200). Keep testing the V-Switch sensitivity and adjust the threshold until it only engages when you want it to (too sensitive a setting will lead to the V-Switch falsely triggering on or off when using the Expression Pedal).
6. When the V-Switch sensitivity is set to your satisfaction, press both Up/Down Footswitches simultaneously to exit."

The expression pedal works really well now and the rp250 sounds good!
Note: Bare in mind that you HAVE to use the right power supply for your multi-effect. Do not mix up 9VAC and 9VDC power supplies used with boss pedals and other effects. This is very important as a fault caused by wrong use of power supplies, wrong polarities or wrong voltage is usually not covered by warranty and could do serious damage to your effect(s).

The Whammy effect now works! Yeah!

Cheers,
Thanos