My ma is having a clear out and she has sent me my old 800XL plus a bonus 2600 I never knew I had?

Any way, I remember I knocked the 800xl in some way. If I am right I plugged the power supply into a C64, it didn’t fit and something went bang. Or it might have been a C64 adapter to the 800XL.

Whatever it was, something is broken. If it is the power supply then I can simply grab another. If it’s the 800XL then any clues how I debug what is funked?