Huge thanks to Remington Goodwin for his EXCELLENT guide! I followed it -- successfully -- to swap out a defective board (the battery compartment microswitch had disintegrated), using a board from another "parts only" SX50 HS from Ebay. Couldn't have done the repair without his guidance.

HOWEVER -- two suggestions that will save a lot of frustration:

1. The "detached wire ribbon" (step 15) that plugs into the back of the I/O board is many (many) times easier to reattach it if you remove the front case (two small screws) and top shutter button panel (1 screw) to gain access to that ribbon cable from the front.

2. Be SUPER CAREFUL when reinserting the I/O board -- watch the almost microscopic plastic plunger on the microswitch. Have the battery door open when reinserting the I/O board; otherwise, you can easily knock that plunger out of the switch. It is so small it is almost impossible to see it -- so go slow and be careful.

Excellent DIY tutorial! Kudo's to the technician!