Hi!

If one was going deep into this, you would have to reverse
engineer a schematic along with data sheets to figure out
what's really going on inside. And that's highly time
consuming. You got the funds to to that?

Please define "the funds to do that". Hundreds? Thousands?

The way these supplies seem to be dropping out, I may spend the money one of
the two ways.

There is always the possibility that there is some latent failure
of the power transformers or such. Those parts will NOT be
readily available if they can be found at all. A 494 is a pretty
common switcher control IC. Used commonly in car stereo amps.

I just don't know where the trouble lies. These supplies die silently and so
far there is only one documented case of one actually blowing a
transformer...which was a rather smoky, fuse-blowing event as I'm told.

More than anything else, I really want to know what is killing them. I have
many other PS/2 systems operating with other supplies that don't run in
anywhere near as pleasant conditions. Many don't cool themselves as well as
these Delta 335/400 watt units do, nor do they have as much output power. As
an example, I have some 94 watt supplies used in the PS/2 Model 50(z) that
have traces which have delaminated from the circuit board and even some sign
of having been *very* hot at one time or another. These also operate under
rather heavy load with fancy video cards, 386 upgrades, memory cards and
network cards. Yet not a one of these has ever given up and quit working,
even under the odd bad set of line conditions.

William