What has been your costliest mistake in this hobby?


For example :I recently learned a hard lesson- I accidentally ran voltage thru my $3000 MC cartridge (kiseki purple heart).  I have a TT with 5 prong connector and a phono cable with a 5 prong connector.  I accidentally swapped where they plugged into and ran electric thru the tonearm into the cartridge.  It was a stupid - not thinking- hasty mistake. When I corrected the problem the cartridge was fried.  An avalanche of four letter words followed!

So what has been your biggest and/or costliest mistake?
polkalover
Cable drop, I added a whole new, meaning to four letter words..
I'm still fixing stuff. A single 300 deluxe VTL, a GG MC275, and two months after that I lost a channel (same side as the cable drop) on my C2500. 

Cost to replace off the shelf, 12K plus. Cost to repair, A LOT of time and money over 2,000.00 in parts alone. TWO transformers, not a single blown fuse, only at the main, THE MAIN. It popped a 20 amp breaker, but not a 5 amp fuse, on the surge protector, amps or preamp...

I must have looked like the Abominable Snowman, after he got his teeth pulled... Yup that was me.

Now I call PG&E and have them shut down WHOLE grid, when I work on my stuff.

Yup, you can blame me, for no power this summer, not the fires.
Doing a cable swap, "Shut down the grid" oldhvymec is at it again. ;-)

Regards