FSP 300 Died. How to Troubleshoot

[bigbeark]

I was using this on a P3C-D board, I put the box away for a while, got it out yesterday and no response when I attempted to power on.

I substituted another PSU and the machine booted up, so this PSU has a problem,

I tested continuity in the plug, OK. Measured ESR of all caps, OK.

Measured ESR of the "yellow suitcase" which I believe is the X caps = 13.54.

The blue tantalums do not read at all on my ESR METER.

Nothing appears burnt or bulged.

I wrote the note re the Fan. It was pretty anemic, but I verified and it is not shorted. I tried the PSU in and out of the case.

Any ideas? I like the fact that this PSU has the extra P4 connector.

[sofTest]

Re: FSP 300 Died. How to Troubleshoot

Check out the resistors. Some FSPs are known to have failed resistors.

[Krankshaft]

Re: FSP 300 Died. How to Troubleshoot

Check for standby power from the ATX connector when it's powered on.

[everell]

Re: FSP 300 Died. How to Troubleshoot

Check your 5vsb - if it is dead, nothing will work.

I had a Powerman FSP300-60BT, probably same model just under Powerman name. Problem was dead 5vsb. The 5vsb circuit uses a 1H0165R pwm chip which has 4 pins coming out of the bottom. Mine had a bad chip. Also the "critical" capacitor was high esr, a Fuhjyyu TNR 47 uF/35 volts.

If your power supply has the same pwm chip, you will probably have a hard time finding a replacement. If replacement is needed, use Fairchild KA5H0165 which is a newer version and works well as a replacement. Also change that critical capacitor.

[kaboom]

Re: FSP 300 Died. How to Troubleshoot

The standby supply in this unit leaves something to be desired. Back in '05, I found some high-res images of this supply and the 'ATX-350-60PN.'

Compared to the 350, this one has:

Transistor for standby power on a tiny little bracket instead of main switcher heatsink
Components cramped around bracket and resulting hotspot
Board discoloration around bracket in units that have been in service for a year or so
GLUE!

Go directly to the standby transistor. There will be a resistor from the emitter or source to the negative side of one of the big caps. If that transistor shorts from improper bias resulting from the 'critical cap' getting high ESR, that resistor will open.

Regardless of what you find, please save yourself the trouble and aggravation and remove that glue! It's all over the DC link cap in that one pic, covering the top of the primary snubber resistor. See how it burns and gets crispy? It also gets conductive! Don't be afraid to remove all the components for the standby supply to clean them, as well as the board.

-Paul

[mockingbird]

Re: FSP 300 Died. How to Troubleshoot

Regarding the 350-60PN I am actually in the process of recapping one, they were sold up till 2009 I think. Thanks for the information.

[kaboom]

Re: FSP 300 Died. How to Troubleshoot

I've removed plenty of components and cleaned them and the board underneath of that useless glue. More supplies use it than don't.

If I go to the trouble of recapping, that junk goes. It's a guaranteed problem- not if, but when. Between primary and secondary isolation barriers and across MOSFET gate and drain leads are the real 'hotspots.'

Is your 350-60PN missing any PI-inductors? I just love how all the caps are on top of each other, with load resistors jammed in there... Remove them. Then just use an old HDD to test the unit out of the 'puter. Or a bunch of 12V bulbs, or a headlight. Those old ignition coil ballast resistors are great for loading 3.3 & 5.

-Paul

[bigbeark]

Re: FSP 300 Died. How to Troubleshoot

I have finally gotten around to removing the standby components as per attached pic.

Many thanks to Everell and Kaboom for your suggestions.

Both the original and the replacement part number are obsolete at mouser, but there are Ebay Hong Kong listings for both parts.

My problem is the resistor. As you can see the wire has gotten really hot.
Can someone identify this resistor for me so I can find it on mouser?

I am assuming both parts are burned out. I will be replacing all the caps on the PCB.Thanks again.

[Wester547]

Re: FSP 300 Died. How to Troubleshoot

Seeing as how this isn't an uncommon failure, is something defective about the Fairchild part 1H0165R? Or do those parts just die when exposed to precarious amounts of heat (when mounted on small heatsinks)? I looked at the datasheet and the only hint of premature failure I could see is that it's only rated at 25C (room temperature or lower). It so happens that my Hipro 300W HP-P3527F3 has that very part.