Yesterday, I thought I was going to perform last rites for my beloved Nikon F4 of the last 22 years. There was absolutely no sign of electronic life whatsoever, no matter what I did (yes, including replacing the batteries).
Just as I was sadly to put it to eternal rest in my vintage camera cabinet, I tried one last thing. I removed the MB-20 battery grip, and put on the MB-21. Ta-daa! A fully functional F4S was resurrected through heart transplant. Good as brand new.
Somehow it was only the MB-20 that had quit. It doesn't seem to do much except keep the batteries in place, but no doubt some circuitry or contacts were broken. I have no plans getting a new MB-20, always preferred the full monty F4s configuration anyway. Looking forward to 22 more years of shooting with this marvellous beast.