Learning with ATX CHIEFTEC 450W PSU

[harp]

I have a little question regardless a way to repair ATX power supply CHIEFTEC MODEL: GPS-450AA-101 A. It is 450w power for computer.

The psu has initial short on +5VSB (purple), and I found and replace shorted diode SB340. After replace, unpowered measurement of all outputs seems fine. All other big double diode on heatsink are ok in secondary side. I connect psu with 60w bulb in serial, and bulb shortley flash as it would be. There is steady 5.2v on +5VSB and PS-ON, on any other is nothing, like 0.00v. So the primary is ok, right?

But, when I PS-ON (green) connect, bulb go fully on, and I hear some very little sound, maybe high frequency, pitch, cracking, "moving arround", something wiered. I cant describe the sound its not consistant, but when hear it I know it is not ok. In 3 seconds or so, bulb is not power off, so I unplug psu. I am not happy to mess with measure on pcb when connected to main, but is not a problem if I know what are looking for and is safe (for chips, pcb) to do so. But I dont. Yet. In that 3s I measure 5V (red) and 12V (yellow) from molex and it is ok.
I do not know how much time I have with 60w bulb fully on, so to not making everything instant dead or worse?
In unplugged state, I do some measurement of common things, diodes and transistor, smd caps, but I not find anything wrong.

What can I do in this case, what is next step?
Any sugestions, experiance tips?
More power?

[kaboom]

Re: Learning with ATX CHIEFTEC 450W PSU

You're choking the APFC with the bulb in series with the AC line. For initial testing with the standby supply, you can use the dim-bulb, but the APFC will try to boost & charge the main B+ cap when PS-ON is active. But with the bulb in series, the line voltage is effectively lowered, so it takes more current to maintain voltage on the main cap. Try multiple bulbs, totalling 300-400 watts, but go in 60-100W steps. Once you're sure it won't blow up, load +5 & +12 with resistors, small lightbulbs, or a "junk" HDD.

It appears that unit is a relabeled Delta, so maybe the attached (partial) schematic will help.

[Per Hansson]

Re: Learning with ATX CHIEFTEC 450W PSU

Usually when you hear sounds like you describe it can be caused by a failing primary bulk capacitor.
So I would try to measure the primary capacitor for both ESR and capacitance.
It might just be completely dead or very close to...

If it is fine then I would continue as kaboom said and use higher wattage bulbs to see if the unit will behave.

[stj]

Re: Learning with ATX CHIEFTEC 450W PSU

whats your mains voltage on planet earth?
100v,
120v
230v?

[Per Hansson]

Re: Learning with ATX CHIEFTEC 450W PSU

45.2,14.4 is in the Adriatic Sea, so I would guess 230VAC on a raft between Krk and Opatija

[CapLeaker]

Re: Learning with ATX CHIEFTEC 450W PSU

A 60w light bulb is too small of wattage. Not sure about this exact PSU, but even the 300w Power Man power supply I repaired recently will not turn on with a 100W light bulb in the light bulb trick. The supervisor IC won’t let it. Put a 150W light bulb in and the PSU starts as it supposed to.

[stj]

Re: Learning with ATX CHIEFTEC 450W PSU

i use a 120w linear halogen floodlamp for psu's
it still wont start some - i need to find an old 500w version

[CapLeaker]

Re: Learning with ATX CHIEFTEC 450W PSU

Thats why I use a 150W bulb to 99.99%

[harp]

Re: Learning with ATX CHIEFTEC 450W PSU

First of all, I thank you each of us, it is nicely to see great feedback with help.

I measure esr in circuit of main capacitor, and it is in ok range. I do not hear sound when I connect psu on main (yes, 230v), but only if I connect PS-ON signal. I suppose that this "schratching" sound is not from main capacitor, but very likely from AFPC. I hear about FPC circuits but not familiar with that.

So, before I get more powerfull bulb, I just wont to know, how to sure distinct a well working AFPC hungry for power, from some random short on pcb, not in output stage, so that progress have sense to me? I mean, if is some short on pcb that I cant locate, then add more power is pointless from repair side of view, at the end of that I finish with blown traces, ic, etc... but finaly located a fail... The pcb is very stiff populated, I cant put even pencil size on some component.

I add some pictures in attach

[stj]

Re: Learning with ATX CHIEFTEC 450W PSU

the sound was probably the pfc coil.
i have a superflower psu that actually clicks like it has a relay in it - very anoying!

[Per Hansson]

Re: Learning with ATX CHIEFTEC 450W PSU

So, before I get more powerfull bulb, I just wont to know, how to sure distinct a well working AFPC hungry for power, from some random short on pcb, not in output stage, so that progress have sense to me? I mean, if is some short on pcb that I cant locate, then add more power is pointless from repair side of view, at the end of that I finish with blown traces, ic, etc... but finaly located a fail...

I don't have a good answer, but you can't bring up a APFC PSU on such a low wattage bulb.
Look at my post here for an example of what you can try:
https://www.badcaps.net/forum/showpo...1&postcount=77

However before you do that please check the soldering of the bulk capacitor, it looks bad to me in the attached photo.
It is also important to check the capacitance because that is the most important metric for a bulk filtering capacitor.

[lotas]

Re: Learning with ATX CHIEFTEC 450W PSU

With soldering, everything seems to be fine here, in these places there are metal through sleeves (like rivets).

[CapLeaker]

Re: Learning with ATX CHIEFTEC 450W PSU

I don't have a good answer, but you can't bring up a APFC PSU on such a low wattage bulb.
Look at my post here for an example of what you can try:
https://www.badcaps.net/forum/showpo...1&postcount=77

However before you do that please check the soldering of the bulk capacitor, it looks bad to me in the attached photo.
It is also important to check the capacitance because that is the most important metric for a bulk filtering capacitor.

Mmhh… a 300W light bulb is a bit much for my liking. My main bulb is a 150W. It seems to have a good balance to get the PSU in working condition. If I load a PSU and test it I don't use the bulb trick. Not sure what others use, but maybe the bulb trick deserves its own thread?

[harp]

Re: Learning with ATX CHIEFTEC 450W PSU

I have desoldered C1 and it is some lower capacitance, but good esr, hoping that is not critical, because replacement I have is too big to fit into pcb. Yes, it is some metal ring shrinked in holes, that I cant desoldered.
Anyway, this is for learning purpose only.

Is there any way to APFC (this time not AFPC ) briefly and temporarly kill down, disable, baypass, whatever simple thing according to shcematic, only for testing time, but for sure,to see if psu is working correctly, with 60w bulb to stay on safe side?
I do not know, but maybe it can connect some points on chip with resistor to somewhere, so that PFC dont even activate, but other chip start normaly working without correction?

I feel that the psu is completly ok, and it should work with tosters or directly on mains, but I dont wish to simply let go practical example to learn something new if I can.

[Per Hansson]

Re: Learning with ATX CHIEFTEC 450W PSU

Ok, the original Samxon capacitor is fine, remember that capacitors have a +/- 20% tolerance rating...

To test the power supply without APFC you can either ground the UCC3818N APFC controller SS pin or disconnect the OVP/EN pin.
You can also remove the entire PCB with the UCC3818N chip on it to disable APFC.

[harp]

Re: Learning with ATX CHIEFTEC 450W PSU

I connected SS pin #13 to ground, but 60w bulb instantly go to full light. I immediately unplug from mains, but in meantime I do not hear earlier mentioned noise, funny cracking...

So, pfc is probably off, but I cant tested rest of circuit on this way. Some other different simple idea to aproaching to test, before everything blow up with toaster?

[Per Hansson]

Re: Learning with ATX CHIEFTEC 450W PSU

Try to increase to a 120w bulb, you can of course use two parallel 60w bulbs instead...

Also note the remark in the datasheet about grounding the SS pin:
Note: In an open-loop test circuit, grounding the SS pin does not ensure 0% duty cycle. See the Application and Implementation for details

[harp]

Re: Learning with ATX CHIEFTEC 450W PSU

I am expecting that psu with stopped pfc is not drawn a lot of power at all, is there anything else that demand more power to "start working more efficiency"? 60w unloaded is way to much... 120w is double of that

[Per Hansson]

Re: Learning with ATX CHIEFTEC 450W PSU

Well, maybe try desoldering the whole APFC board then, I'm not sure it is disabled now.
Or disconnect the OVP/EN pin instead.

[harp]

Re: Learning with ATX CHIEFTEC 450W PSU

OMG I am thinking that you are for shure that groundes SS is completly disable pfc...

So, I look at pcb, and some traces go from pfc board indirectly to 3845B chip... it is look to me like complete controler from two parts/location?
If I took pfc board out, what behaveour I can expect from 3845B regardles to mosfet?

I only want to know how to test psu in safe way (low current), and is there some common way, easy way, to do so?

Here I learn about pfc and general how work, so it is logicaly that it has to be somehow bypassed to perform a low current bulb test. But maybe it isnt possible (at least a easy way) if some other ic depends on it.