Came across this nice looking 8860A recently for $28 and just couldn’t pass it up. I remember when these stackable Flukes came out in the early 80’s and always thought they were kind of neat looking, although well out of my price range at the time! Anyway, here’s a quick shot of it powered up in auto mode with no signal. It’s in very good shape.
I decided to pop the cover off and take a look inside. Here it is with the A3 controller board pulled out. There are a couple of axial lead electrolytics behind it that I’ll be replacing but they look to be in pretty good shape for now.
So… I’m glad I decided to take a look inside. Check out C7 on the main board, a 4700uF 16volt electrolytic installed backwards! This is a filter cap for one of the 5 volt supplies and after looking at some pictures taken by user Spawn over at eevblog, this is the original cap and came from the factory this way! Doh! You can see what happens when an electrolytic is installed backwards. I’m surprised they didn’t catch this at the factory. Notice the (+) symbol on the circuit board.
Replaced the caps, with some new Nichicons I had on hand and buttoned the case back up. I hooked it up to my Power Designs 2005A set for 10 volts indicated on the Fluke and let it run all night. Totally stable. Still need to go through the calibration procedure though…