I got an Apple IIe recently with no power. Here's a quick account of what was needed to get it working in case it's helpful to others.
The system was loaded with a bunch of expansion cards. Those were all removed, but still no beep. The power LED on the MLB would sometimes pulse and the PSU would chirp. Occasionally there'd be no signs of life. A couple of times the LED would stay lit but the 5V rail was <2V.
Replacing the caps, including C7 which is a common failure point made no difference.
The non-zener diodes each had a leg removed and tested. All were fine.
The 3x zener's were swapped and the PSU started working perfectly. I replaced the original 1N4606's with more common 1N4148's.
The machine beeped and booted okay once those diodes were replaced. I haven't tested the old parts individually yet, but will just leave all of the 1N4148's in there regardless.
The system was loaded with a bunch of expansion cards. Those were all removed, but still no beep. The power LED on the MLB would sometimes pulse and the PSU would chirp. Occasionally there'd be no signs of life. A couple of times the LED would stay lit but the 5V rail was <2V.
Replacing the caps, including C7 which is a common failure point made no difference.
The non-zener diodes each had a leg removed and tested. All were fine.
The 3x zener's were swapped and the PSU started working perfectly. I replaced the original 1N4606's with more common 1N4148's.
The machine beeped and booted okay once those diodes were replaced. I haven't tested the old parts individually yet, but will just leave all of the 1N4148's in there regardless.
