Removing PFC from PPFC PSU?

[Dan81]

So I've recently got a dead nJoy 500W PSU. ERL39 transformer (real),2SC3220 transistors, sleeved cables and pretty thick heatsinks, all nice stuff (except caps which are ChengX but that's not the point for now). It even has a pretty beefy bridge rectifer. (although no heatsink on it)

It came to me with two bad Fhy 1000uF 200V caps. I replaced them with some 680uF 200V caps and bypassed the PFC connector, and temporarily replaced the glass fuse with a 100W lightbulb.

On powering on, I only get a flash of the light bulb and a quick click (about a split second) and no fan movement or nothing.

Is there anything I should remove? I have a feeling I haven't fully disabled the PFC circuitry.

I really wish to fix this PSU since it's pretty much full of parts. Of course, after fixing it (means when it will finally power on fine and voltages will be within range) it will probably get back some new 1000uF 200V caps (hope I can snatch some Pannies or Rubies for it to go with the black PCB) and a nice recap on the whole secondary.

Oh, and it has dual rails, and I'm not even kidding. The PCB literally has two separate 12v spots where the wires go.

[eccerr0r]

Re: Removing PFC from PPFC PSU?

PPFC is basically just filtering the input a bit, I'd think it's a lot more reliable than APFC which would be harder to bypass/rebuild especially if it would need a tripler or something to get the voltage needed for the next stage.

Not sure why one would want to remove PPFC?

At least if the light bulb isn't solid on, you don't have a short... does it work? I'd imagine the 5VSB should work with the light bulb in that position?

[Dan81]

Re: Removing PFC from PPFC PSU?

PPFC is basically just filtering the input a bit, I'd think it's a lot more reliable than APFC which would be harder to bypass/rebuild especially if it would need a tripler or something to get the voltage needed for the next stage.

Not sure why one would want to remove PPFC?

At least if the light bulb isn't solid on, you don't have a short... does it work? I'd imagine the 5VSB should work with the light bulb in that position?

No voltages come up, just a click from the primary heatsink. The bulb does flash once though. Same behaviour if I short the green wire to GND.

I want to remove the PPFC because I installed it in a PSU shell that doesn't have the space to screw in the PFC.

[eccerr0r]

Re: Removing PFC from PPFC PSU?

Well if the bulb lights temporarily, it's charging the primary caps and likely you didn't cause an open circuit while removing ppfc.

Now you just have to go through regular debugging starting with whether 5vsb is working? then you can go and see if the controller ic is good for starting up...

[Dan81]

Re: Removing PFC from PPFC PSU?

I'll put up the multimeter and check.

Although I have a feeling 5vSB is not working even though the caps aren't bulged (ChengX tho, going to replace them) they may have failed.

I also have found some pics of a non-PFC variant and will see what components will need removing in case I didn't fully disable the PFC circuit.

[Dan81]

Re: Removing PFC from PPFC PSU?

Okay, some updates:

1. The switchers weren't 2SC3220 but 2SC3320.
2. Both switchers were kaput - at least one of them had a huge burn mark on it.
3. 5vSB did come up even with the bad 3320s, strange enough, at 5.21V.
4. I'm not sure but there might be a bigger short somewhere or I must've screwed up somewhere, because after replacing the bad 3320s with a pair of 2SC4106s, the PSU would click and the lightbulb would constantly flash. A few seconds later smoke came out of one of the 4106 (interestingly the same one near the main transformer, just like the 2SC3320 that had a burn mark) and I quickly turned off the PSU.

Any ideas what could be wrong with it? I'm ready to give up on this as I've replaced a whole lot of stuff.

[eccerr0r]

Re: Removing PFC from PPFC PSU?

5VSB has its own switcher, so the main switchers don't need to be working for 5VSB to be up.

hmm. Wonder if the main controller chip died after the small caps blew up. Not sure...

[Th3_uN1Qu3]

Re: Removing PFC from PPFC PSU?

If you have a bipolar transistor for the main 5VSB switch then the main controller chip is going to be on the secondary and have absolutely nothing to do with the 5VSB. The standby supply is what turns the main controller chip on. I am 95% sure you have the classic two transistor switch circuit for 5VSB, check out some ATX power supply schematics on the internet and you should find a pretty good match for your circuit, which will help you troubleshoot it.

[Dan81]

Re: Removing PFC from PPFC PSU?

5VSB has its own switcher, so the main switchers don't need to be working for 5VSB to be up.

hmm. Wonder if the main controller chip died after the small caps blew up. Not sure...

Main chip is a KA7500 and doesn't look burnt.

And for the record, it wasn't the small caps that blew, but the big 1000uF 200V caps that blew.

[Dan81]

Re: Removing PFC from PPFC PSU?

Well, I finally fixed it.

Seems that somehow the standby switcher was bad too. I replaced the 2SC4106s with another pair of 13007s (temporarily, I plan to get some new 3320s soon) and the IRF3N80 with a BU3150AF from a old iMicro PSU and it came to life. Also main caps were already replaced with Ricon 680uF 200v caps I had from another PSU. Not going to replace these since I don't have bigger replacements and they work fine for me.

I replaced the casing with one from a RPC 500LBL PWPS-050000L-BE01A (no joke, that's the model number). Rectifiers are 30A for both 5v and 3.3v and 12v has two 16A rectifiers in parallel. (it originally had 2 shorted 20A rectifiers.)