Both pedals had an issue with selecting certain modes. The DD-3 had the long delay in the knob positions "M" and "L", medium delay was not selectable most of the time. And if it worked, it went back to the long mode after a few minutes. Totally unreliable. The DD-6 did overall produce the longest delay time in most modes, only the shortest and longest delay modes were correctly working; reverse delay and WARP mode also only produced the same sound of the longest delay mode.
I managed to repair both pedals to make all the modes reliable and working properly again. Not to my fullest satisfaction, though.
The problem seems to be that the mode switches are normal potentiometers with detents and with three solder legs. They are not true switches anymore as they were in the past. My guess is that these potentiometers have worn off somehow. The resistor values that they used to have at those certain detent points don't seem to be correct anymore. I think that the electronic scanning of the mode potentiometer does only work with accurate resistor values with very little tolerance.
In both cases I replaced the hard (if not impossible) to come by mode potentiometers (with detents and reduced travel path) with standard potentiometers.
In the case of the MIT SMD DD-3, fixed with a standard potentiometer, the effect was in short delay mode in minimum position ("S"), then in medium and long delay mode at the correct marks of the knob metal plate ("M" and "L"), then for the rest of the potentiometer's range it was in Hold mode, also beginning at the "Hold" mark.
Today I did the same with the DD-6, where I already double-checked everything before ordering a fitting replacement potentiometer. With the new potentiometer all the modes are working correctly again. I have to clean and assemble it yet, but I guess that also in this case all the modes will switch at the correct positions that are marked on the knob metal plate, beginning at the Warp mode at 07:00 up to the 2600ms mode at 01:00.
The only "problems" are that you don't have the detents when using normal potentiometers as a replacement, so you don't instantly feel it when you are switching modes, and the mode knobs will have the full travel path of a normal potentiometer (270° to 300°) and don't stop at the mark of the last mode in clockwise direction. If you can live with that, you can easily fix your faulty pedal this way.
this doesnt bode well for the PS2 i got coming in the mail
