About a month ago, I purchased a broken Keithley 199 multimeter off ebay for about $70 including shipping. From everything I’d read, it was a pretty accurate 5.5 digit, 310,000 count multimeter with a nice bright LED display (as opposed to the Fluke VFD, or HP non-backlit LCD displays). Having bought sight unseen, I wasn’t sure what exactly was broken. It could just be simple user error, or something more serious, but from the age of the unit, it should be fairly repairable.
And thankfully, the manual supplied by Keithley (available here, via KO4BB, without registering), has wonderful block diagrams, layout images, and schematics. After receiving the unit, I found it was indeed non-functional, with wildly varying readings. All the buttons worked, and it would switch ranges, but the readings never worked.