Power supply for Boss RC3 looper

[dude]

My Boss RC3 looper will not operate on several wall warts l've tried. Boss says to use their BOSS PSA 9V adapter only ($21.00), 9vdc is 9vdc in my book all day, the polarity is center (-) on the RC3. This pedal does not have the polarity symbol marked, all my other pedals do have the symbol ands it center (-). The specs on the RC3 schematic say the RC3 is center (-), runs on a 9vdc power supply.  But every 9vdc (- center) power supply l tried does not work, some light up all the lights and blink, some to nothing, none turn it on.  I've checked the voltages on all the power supplies, range from 10 to 13 vex and 300mA to 500mA. The specs say the RC3 draws 9vdc @ 70mA. I had one power supply that had a selection of between 4 and 15 vdc  and 100mA or 300mA switch, with my meter l selected the closest to 9vdc, the 7.5v setting gave me 10.2vdc so I selected that, all the setting are center (-).
Here's the results: the pedal works with 10.2vdc and only the 100mA setting. If l select the 300mA setting on the power supply, no go, unit shuts off.
I'd like to know why, it answers the reason why all the other power supplies didn't work they were 500mA. I thought that amp rating on power supplies was the max draw the pedal supplies. Why would a pedal that draws 70mA work on a power supply that only has 100mA's capability but anymore amperage "capability" to put out more amperage not work. Please school me.

[dude]

I assume that most that read this have no answer as to why and I can see that, doesn't make sense. I googled the supply adapter for the RC3 and a lot of people had issues with many not playing, some say no issue but most had problems. None mentioned the ones that worked had low a low amperage rating, I just  happens to have one out eight that worked and it was a low 100mA rating...? Maybe it had something to do with the plug end...?

[Latole]

  9vdc is 9vdc in my book all day,

Wrong. Read better book