Sorry for the long story, but... I picked up a IIe from a thrift store a couple of weeks ago. Looks like it's from 1985. I got it home, hooked it up to a small portable B&W TV that had a composite input, and it seemed to work fine. I got the "beep", ran/passed the diagnostic test, switched to ROM BASIC and ran a few short programs. No disks to test the drives yet.
Later I bought a Sanyo DM 4512 security monitor off of eBay. It's also from around 1985. I eventually tracked down the adapter so I could plug an RCA plug into it. (All these old Sanyos seem to have RF jacks in the back, but it's really composite input, isn't it? I hope???) I powered it on not hooked up to anything and it didn't seem to show any immediate problems.
Of course, I knew I had to replace the Rifa cap in the PSU (AA11040-B), so I ordered a variety pack of X2 capacitors off Amazon and swapped in a new 0.1u capacitor, which is the correct capacitance for C1 from what I gathered. I first double-checked the replacement's capacitance with my meter and it was right on the money. (Interestingly, I tested the original Rifa after I got it out, and it clocked in at 0.13u. Not sure if that means anything.)
The computer powered on with my little TV as a monitor and the new PSU cap. LED light on motherboard came on. Got the beep, etc. So far so good...
Then I powered down and hooked up the Sanyo to the Apple for the first time. I think I powered on the Sanyo, then the Apple, but it might have been the other way around.
Anyway, I got nothing. Not a pop. No smoke. Just a dead computer. No LED, no beep. I disconnected the monitor and tried again a few days later with no montor attached. Still nothing.
Checked the power rails via one of the expansion slots and also a couple of rails at some of the chips (where is the best place to check power on the motherboard anyway?) Nothing. Then checked voltages at the end of the PSU-to-Motherboard plug (so, not under load), and got nothing. Confirmed that the power cable from mains to the back of the PSU was carrying power.
Opened the PSU and checked the fuse. It's not blown! The cap looks fine, but my next step is to pull the PSU board out and poke around a bit.
So... did I just get a bum replacement capacitor that could only withstand one power-on before failing? So the Sanyo monitor is just a coincidence? (But that capacitor failing wouldn't take down the whole PSU, would it?)
Or did the monitor do something terrible (I don't know, pull a ton of current??? Send voltage out the video input???) that hosed the PSU in general--or worse, the motherboard--and the new capacitor is just a coincidence?