I have a problem with the boss ch-1 pedal. It hums(whining sound or smth) loudly, when connected to adapter. Everything is fine with the 9volt battery. I don't think it is the adapters fault, because I have it connected to a Dunlop wah and it gives 600mA, so 200mA for wah and 200mA for chorus. I bought the pedal on eBay, so it may be faulty somehow. I think that it's an electronical problem, but could anybody give me some tips, how this can be fixed?

maybe try taking the battery out and then plugging in the adapter? no clue but it's probably something i'd try as a first step
Sure, but what test's are you thinking of? Unfortunately I don't have a multimeter, so I can't check the voltage :/