Re: suggestions for locating, testing and replacing defective components on very closely spaced PSU?

If the caps have a dome for a top, they're defective. Replace them with 105°C equivalents.

The only way you're going to get easy access to the solder side of the PCB is to remove the sheet metal case. If you can't locate the capacitors from the solder side of the board, shine a flashlight through the PCB, from the components side of the PCB. That will produce a shadow of the case.

Another way is to take a photograph of the components side. Use some photo editor to reduce the size of the image so that it's actual size (1:1). I use Irfanview:

Maybe get a replacement used power supply:

Four are domed, but I am going to replace some near the domed ones as well.

I think the board was a little too thick and/or I couldn't get the flashlight or work light close enough (tried both).

I was able to use my flat bed scanner to scan both sides of the board. The component side didn't scan all that well as I think there was too much spacing caused by the components that separated the circuit board from the scanning surface to too great of an extent. However, with enough fiddling in Affinity Photo, my photo editor, I think I was able to get the alignment close enough to know where the caps are from the solder side.

Thanks for the suggestion, but those are as expensive as more modern lower end 80 plus ones. I'd probably go with a lightly used and recent

Visual bulging of the electrolytic capacitors is NOT going to identify all the failing capacitors. The physically smaller electrolytic capacitors do not produce domes. Instead they leak liquid electrolyte which appears as a brown tar on the PCB around the base of the capacitor. Some smaller electrolytics blow the rubber plug out of the bottom of the capacitor. Some show no visible indication of a problem. Fortunately, an ESR tester will usually show a problem. Since you now have the power supply disassembled, you might as well test every electrolytic capacitor. When I was still repairing power supplies, it was not unusual for me to find a power supply with almost every electrolytic capacitor exhibiting high ESR measurements. When in doubt, replace everything that exhibits high ESR.

Incidentally, I have three ESR testers. When I started finding boards with all the electrolytics appearing to be defective, I began mis-trusting my initial ESR tester:

It works well with G10 PCB material and not so well with cheaper phenolic.

Agreed. Using a scanner as a camera is limited by the scanner's depth of field. A scanner is in focus only when the item being copied is directly in contact with the glass. At best, you might have 1/4 inch of depth after which everything is out of focus. Digital cameras, cell phone cameras and USB cameras have the same problem. You can increase the depth of field if you stop down to a small f-number (focal-length / aperture-diameter) which requires using rather bright lights. That's why photo studios use big bright lights.

This one?

You didn't include your parts and repair time in your calculation. Of course a modern power supply would be better than a 20 year old used power supply.

I'm not sure what manner of computer case you're using, but the older Compaq tower cases required some rather long 12V/5V power cables. That's why I suggested an identical replacement (with long leads) instead of a modern power supply.