PC P&C Silencer 420W

[Colt45ws]

Re: PC P&C Silencer 420W

Thats what I thought, and is why I have three of them. That was 3-4 years ago, though. Now I look here and on JG so I have mixed brands now.


Those glass diodes are the little red things?

[Toasty]

Re: PC P&C Silencer 420W

Yes. Look to be D305/306.

[Colt45ws]

Re: PC P&C Silencer 420W

Im getting 22ohm across them either way with the probes. But they are in parallel with a resistor, so I should 'see' the resistor one way and virtually no resistance the other, right?

[Toasty]

Re: PC P&C Silencer 420W

From what I can see that resistor's marked 220. That's 22Ω and you'll read that no matter which way you probe. Diode check setting, correct? If it read lower one way, then I'd say the diode was shorted.

Are the transistors reading okay?

If you don't find anything, then I would order the repair parts and the new caps. Get it back together and do the series lamp to see what happens.

Attached all the photos here as I discussed in the other thread and also so I don't have to keep jumping back to Page 1.

Toast

PS: What happened with the coil? Did you get it inspected?

[Colt45ws]

Re: PC P&C Silencer 420W

Reads 22Ω either way. Diode check shows .015v (?) I checked some of the other SMD diodes on the board for comparison and most are around .5v with one other at .02v. It would seem to me the ones that are low are shorted, right?
The transistors are not shorted.
The coil has so much of the glue and Im not sure how to remove it without damaging the coating.

[Toasty]

Re: PC P&C Silencer 420W

Not necessarily. Coils and caps will screw with a diode check or ohmmeter. When you get those kind of reading, you have to get it out of the circuit to be sure. Unsoldering one leg is a quick way, but SMD's don't lend themselves to that easily. Leaded ones do.

[Colt45ws]

Re: PC P&C Silencer 420W

Hmm, on the output side, all the FETs have the two outside pins shorted. Normal?

[Toasty]

Re: PC P&C Silencer 420W

They read shorted or they're wired together? Sure they're FETs? Again, surrounding circuitry. They're usually pumping coils.

[Colt45ws]

Re: PC P&C Silencer 420W

I was not sure on the FET part right after I posted and saw BDxxx by each of them on the board. They are going to coils; so that would explain that?

[Trinite]

Re: PC P&C Silencer 420W

Are you sure those aren't the rectifiers? They look like FETs because they contain two diodes and thus require three input leads.

[Colt45ws]

Re: PC P&C Silencer 420W

I took a picture of the the whole bottom board and of the coil. The coil actually looks more burnt towards the top of the glue, rather than where the glue was black which is the clean spot.

[4m0k]

Re: PC P&C Silencer 420W

Any progress on this one? I have Corsair VX450 with almost the same symptoms (no burnt coil in mine). Shorted: q302 (18n50), d304 (stth8s06d), d303 (1n5406).
I am going to replace all of the above and also two liitle caps: c308 (22uf 50v) and c104 (47uf 25v), though I'm still looking for the spares.

[kaboom]

Re: PC P&C Silencer 420W

What I don't like about these APFC units is that they seem to be designed for 200-240V input. At 120V in, the PFC booster has to supply much more power to get the main bus up to the 360-400V it's regulated at.

In my opinion, the booster coils are way too small- not big enough or enough copper. They get way too hot and when they finally get shorted turns, the semis go bang. Or if the DC bus cap opens up, there's no place for the inductor to dump its current. You get insane voltages that destroy everything.

This whole idea was forced upon us by a few 'influential' countries in Europe. Instead of upgrading their backwards secondary-level (416Y/240, 380Y/220V) power distribution systems, the whole world has these little afterthoughts instead. The very fact that those coils overheat and the semis need a heatsink proves that they _reduce_ the overall efficiency of the supply...


One thing to verify is whether the IC on that little board has been damaged. If the PFC FETs turned into a piece of wire, the PFC IC will be backfed line voltage. In that case, the replacement FETs will be destroyed by an IC that puts line voltage to the gates. If you can find the datasheet for your particular PFC IC, see if you can power it up by providing a sort of aux supply for it. Now you can see if the gate drivers are OK.

-Paul

[Th3_uN1Qu3]

Re: PC P&C Silencer 420W

The very fact that those coils overheat and the semis need a heatsink proves that they _reduce_ the overall efficiency of the supply...

PFC is not about power supply efficiency it's about power grid efficiency. As for the booster circuit, it's the designer's fault if they aren't spec'd for 120v operation too. Universal input supplies have been around since way before PFC.

[PCBONEZ]

Re: PC P&C Silencer 420W

Even on the grid it only increases efficiency on paper.
Specifically the paper in the accountant's office.
.

[kaboom]

Re: PC P&C Silencer 420W

PFC is not about power supply efficiency it's about power grid efficiency.

I realize that. Instead of 5-10 amps just before every positive and negative voltage peak, when instantaneous line voltage exceeds that of the input caps and they recharge, the PFC 'booster' spreads that current out over the entire 360 degree cycle (hopefully). Those old secondary dist ckts, with transformers too far apart, get 'flat topping' of the sine wave from the line conductor resistance.

Power supply _unit_ efficiency goes down since we have a 'power supply feeding a power supply.' The POCOs love it- people think they're 'being efficient' but every one of those PFC boosters has losses. 10 watts here, 15 cents there...

-Paul

[Th3_uN1Qu3]

Re: PC P&C Silencer 420W

Unfortunately as PCBONEZ said, this doesn't help as much as one would think, because there's still all those crap swirly bulbs with not even an attempt at PFC. Computer power supplies are far from being the worst offenders when it comes to mains waveform distortion.

[everell]

Re: PC P&C Silencer 420W

Looks like this thread is going in the same direction as our previous interesting (and heated) discussion on APFC. I would like to thank kaboom for his take on the matter....the booster coil gets too hot when psu is operated at 110 VAC. It is having to do twice as much work as those psu operated on 230 volts in Europe. I would also like to thank our Romanian engineer.....that he says the wrong core is being used on the booster coil if it is overheating. That is correct, but if the Chinese manufacturer used a cheaper (cost out) core, we are stuck with a time bomb, which in a few years goes "kaboom". My take on it is, the two FET transistors are shorted, the coil is either shorted or intermittently shorting due to overheating, and some surrounding components may also be bad. Changing only the FET transistors will not solve the problem. I fixed one.....after feeding several sets of FET transistors to failure. The coil is hard to troubleshoot as it may measure OK, but when in operation is bad.

And special thanks to pcbones......APFC does not help or save money for the computer owner. AND it does not necessarily help the power company either. For sure, only the politicians and lobbyists are pocketing extra money.

[Th3_uN1Qu3]

Re: PC P&C Silencer 420W

I would also like to thank our Romanian engineer.....that he says the wrong core is being used on the booster coil if it is overheating. That is correct, but if the Chinese manufacturer used a cheaper (cost out) core, we are stuck with a time bomb, which in a few years goes "kaboom".

That would be me. Thanks... although i have about 3 more years till i can be officially called an engineer. Now that you mention it, if the manufacturer used a cheaper core with significant thermal aging, in the long term the core losses increase so the coil gets hotter and hotter... till the wire insulation melts and turns start shorting to each other. Boom.

I fixed one.....after feeding several sets of FET transistors to failure. The coil is hard to troubleshoot as it may measure OK, but when in operation is bad.

It is hard to troubleshoot if you don't have the adequate equipment. I don't either... but i've read about a simple circuit that hooks up to your oscilloscope and measures saturation current of an inductor. Stay tuned.

[everell]

Re: PC P&C Silencer 420W

...till the wire insulation melts and turns start shorting to each other. Boom.

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