I have a Digitech QP-2286 electrical tester and it is not working, I would like to have it repaired if possible?

It's possible that the Harmony foot switch has become damaged or faulty. One thing you could try is to unplug the pedal from power, disconnect the footswitch from the unit, and then reconnect it to see if that resolves the issue. If that doesn't work, it could be a more serious issue that requires repair or replacement of the footswitch. You may want to try contacting Digitech customer support to see if they have any troubleshooting suggestions or if they can provide guidance on where to find a service agent in your area.

I could not locate instruction for this watch.

A possible set of instructions for some type of digitech watch is bilingual at the link below. Let us know if it works or not, please.

http://www.berklix.com/~jhs/txt/watch/digi-tech/#time

You can order one here: http://www.manuals.club/results_alpha.php?ctext=DIGITECH+QP+2288

Most likely it is the power supply, but if you have a unit that uses the same voltage, you may want to try it. Another possibility would be the power input jack or where it is soldered to the board. If you're not comfortable working on those elements and the PS doesn't work out, take it to the shop.

I am repairing a Digitech QM156 for a friend - someone has been
stuffing with the trimpots - so it's way out of calibration. RV9 on the current sensor board, corrects the zero (most systems have this as an external control. However the volts range etc is way out of whack. Does anyone know what each pot is supposed to do??
Don't want to junk a perfectly good instrument.
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Usually the manuf. have diodes used as protection against over voltage or adapter polarity issues. Try the correct adapter (sleeve and tip have specific voltage polarity...check for drawing denoting each) and if it fails to power the unit up, it's probably time for Digitech authorized repair.

The buttons are probably scanned as a matrix and possibly a circuit board has been cracked causing wrong data to go to the microprocessor in it. It is unlikely this will be a DIY fix so you should contact Digitech for a repair facility.

Here is a link to the manual:ftp://ftp.digitech.com/pub/PDFs/Manuals/RP1000/RP1000%20manual%2018-0597-A.pdf It is highly unlikely that you will find a schematic unless you know a service tech for a music store that deals Digitech. Also you will need some specialized tools. Here is their contact info:http://www.digitech.com/dealers/service_lookup.php If you are a tech you can always contact them.

Check the power adapter. It sounds like it is the wrong unit or it has failed and is not producing the correct voltage.

Try contacting their service center rep at (801)566-8800. They might send you a schematic for the pedal if you explain your situation. They do recommend using the original power supply PS0912 which should still be available. Hope this helps.