Coolermaster RS-460-PCAR-A3 Repair

[squeeish]

Hi! I have this same exact PSU in a computer my dad brought home to test. It worked for years but the moment we turned it on in our house our circuit breaker tripped and there was a faint burnt smell from the PSU. The rest of the computer worked fine with a replacement PSU.

Now that I've got some free time I would like to repair it. The internal fuse was blown (250V 12A), so I replaced it but my circuit breaker tripped again when I powered it on. The new fuse remained unharmed.

Could anyone help me out on my next steps? How do I test +5VSB?

I have a multimeter and some motherboard recapping experience, but the capacitors look fine visually (I ordered a ESR meter from ebay.. will take some time to arrive). I have no PSU experience or knowledge though.

[mariushm]

Re: Coolermaster RS-460-PCAR-A3 Repair

Please post clear pictures of the boards inside.

The fuse blows because something is broken after it.

Usually, a component is shorted. You can check components to see if they're shorted or not by putting your multimeter in continuity mode and touching the pins of that component.

Another possibility is a diode no longer conducts in only one direction, it's now faulty and goes in both directions causing a short. Put your multimeter in diode mode and measure each diode twice, switching the probes around for the second measurement.
You should only get a value on your multimeter for one measurement - if you get two results, that diode is faulty.

In a computer power supply, usually the main switcher transistors fail, or the resistors and film capacitors near them, or the pwm chip controlling the pulses going to the transformer.
Less often, the Active PFC circuit breaks down.

Won't be able to point out something for you to test without some clear pictures.

[squeeish]

Re: Coolermaster RS-460-PCAR-A3 Repair

Hi mariushm!

I tested all the diodes I could see. There are two zener diodes (ZD1 and ZD2) that seem shorted both ways, not sure if that's the behaviour for zener diodes. The rest of the diodes are fine, except for D15 that gives me a short beep in both directions. D23 gives a long beep in both directions.

Here are some pictures. I have no idea which parts are the switcher transistors/active PFC circuits though. Let me know if you want more pictures at certain angles.

[mariushm]

Re: Coolermaster RS-460-PCAR-A3 Repair

Unfortunately, the pictures are shot from too high up and they're too small in resolution to be of any use.

For example, I can't see on the back of the PCB what it's written. I guess you made these with a phone... it would really help if you make the photos with a digital camera that has macro mode or something like that.

And it would help if you post them here as attachments ... you get a button to attach pictures to your post if you click on "go advanced" below the text box.
You can upload very large pictures, up to 2-3000 pixels, and that certainly helps.

Zener diodes are indeed special, they block up to a point where a certain voltage is reached and then they conduct. Depending on what zener diodes they are, you may "activate" them with your multimeter.

This video explains how zener diodes work and how you could test them, but I agree not everyone has a power supply that has a current limit indicator :

http://www.youtube.com/watch?v=5OcoF0nkgng

D15 and D23 may be bad, but again, without actually being able to see where they are, I couldn't tell you for sure.

One thing that's important to notice, if you measured using diode setting on your multimeter, than they're probably bad. If however you measured with continuity, it's possible the diode is in parallel with a resistor that's shorted, or a capacitor.

If you want to be absolutely sure, you have to desolder the diode and test it with your multimeter in diode mode. With leads connected one way, the meter should list the voltage drop on the drop, with leads inverted it shouldn't say anything (diode blocks test current)

The ICs on the heatsinks should also be tested, but it's a bit harder to explain how to do it without actually seeing what ICs are there.

You usually check them with the multimeter in diode mode, testing pin 1 and 2, pin 1 and 3, pin 2 and 3.. there should be voltage drop in one direction and nothing in the other way... but which is pin 1, 2,3 depends on the IC (gate, drain, source etc)

[squeeish]

Re: Coolermaster RS-460-PCAR-A3 Repair

Hi mariushm, I realised that a few minutes ago and I edited them. Can you see them now?

[squeeish]

Re: Coolermaster RS-460-PCAR-A3 Repair

Anyone?

[Pentium4]

Re: Coolermaster RS-460-PCAR-A3 Repair

This PSU doesn't have active PFC so you don't have to worry about that. The switching transistors are attached to that heatsink closest to those big Elite caps. Do any of them looked burnt or cracked?

[squeeish]

Re: Coolermaster RS-460-PCAR-A3 Repair

This PSU doesn't have active PFC so you don't have to worry about that. The switching transistors are attached to that heatsink closest to those big Elite caps. Do any of them looked burnt or cracked?

No burns or cracks on any component as far as I can tell, although I'm pretty sure I smelt a little burning when the PSU shorted out the first time.

The diodes are glued onto the board and I broke one while attempting to remove it.

Looks like it's not worth the effort to repair this PSU?

[venksp]

Re: Coolermaster RS-460-PCAR-A3 Repair

Is there any Schematic available for this PSU. I too have the same PSU. All voltage outputs are Ok except the PowerGood. I replaced a Resistor 4.2K going to PGI input. Now the PGO - shows 2.8 Volts, but all other Voltages show up and start to decrease and go back to zero in a few seconds. What could be the Problem.

[tiny68]

Re: Coolermaster RS-460-PCAR-A3 Repair

I just repaired one of these power supplies. One of the 1000uF 10V Caps located just under the mains switch was blown. There are two of them and they had a section of heat shrink on them which made it difficult to inspect for obvious leakage problems. Once the sheath was removed I could see that one had vented form the top.

[Quaddro]

Re: Coolermaster RS-460-PCAR-A3 Repair

this psu using same structure as acbel 420.

Well, you must to use lightbulb trick to detect the shorted component.

Usually any psu using offline power ic, this component is the culprit.
Check the tny 277 transistor.
Try to pull out the transistor.

also check the r31 as fuse transistor.
This one usually open if you have shorted component.

[everell]

Re: Coolermaster RS-460-PCAR-A3 Repair

Hello squeeish,

I could not tell what country you are from, so will ask if you are using 115 VAC or 230 VAC. This is important to know. There is a switch on the back of this power supply to set up how it is used - set to 115 VAC or 230 VAC.

You mentioned that the power supply worked OK at your dad's house, but immediately blew up at your house. If you and your dad use different power company voltages, setting the power supply to the wrong setting could blow it up. So lets start with something simple. Is this switch set to the correct voltage?