Hardware Insights Forum

I got a Sun Pro PSU (Branded Thermal Master) that I wanted to improve just for fun. It's similar to the one in the PSU roundup, except it has PI coils on the output. I will post some pictures later. One of its original switchers failed open (TO-220 13009) I replaced both of them with TO-247 D209L's with identical specs to the 13009's except the bigger package.

Other changes:
replaced 330uF input caps with 820uF that tested good.
Replaced four 2A diodes with 8A bridge
replaced the original 12V ultra fast with a 20A schottky (And added a second identical one in parallel)
Added an identical 20A schottky in parallel on the 5V rail
Upgraded the 20A schottky on the 3.3V with a 30A schottky
Replaced failing Te Bao fan

Besides the primary, all of the other caps are stock.

The PSU will not power on, but it gets 5.03V on the 5VSB. When the power button is hit, there is a quiet "tick" and that's it. Pressing the power button again, it does not make the "tick" sound until unplugged, replugged in and trying again. I can't for the life of me find any solder bridges, or bad joints. Is it possible that the PSU doesn't like all of the schottky rectifiers?

You could try putting the fast recovery rectifier back in. I know some PSUs don't like using schottky rectifiers on the 12V rail. Also check the rails with a DMM. Just make sure none are shorted either to ground or each other.

c_hegge wrote:I know some PSUs don't like using schottky rectifiers on the 12V rail.

Why is this? Just curious...

I'm not too sure exactly why. There was some discussion about it on badcaps when I was rebuilding my Rexpower 400W. See post 34 in this thread (http://badcaps.net/forum/showthread.php ... t=rexpower)

When goodpsusearch replaced a BYQ28E-200 (10A 200V ultra-fast) with an ESAD83-004 (30A 40V Schottky), the voltage rating was inadequate for the task, which caused it to overheat and burn out in less than a minute. Presumably the same thing happened here. I'd replace the +12V rectifiers with 100V units and see if that fixes the problem.

I haven't had time to get back to this yet but I will try swapping out the silicon to see if that fixes it.