19vdc? This video might help you if I'm right about the mixer brand. https://www.youtube.com/watch?v=ZilcEagVCdI - Modern Tech Fail: Behringer Eurorack UB1202 Repair
I should have included all the specs for the mixers.
The wonky one is a Tascam MZ223 its (short) replacement is close to a Behring X2442USB but much older.