DELL OEM H240AS-00 (HIPRO) ~ major blow up!

[stj]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

o.k. it could be a bad output capacitor, diode or opto isolator just for example.
put the original resistor back - it's a fuseable safety part!!

[rayfloyd170]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

o.k. it could be a bad output capacitor, diode or opto isolator just for example.
put the original resistor back - it's a fuseable safety part!!

thanks for the advice. i will do what you said and give my feedback after that.

[Per Hansson]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

Actually before replacing the caps and resistor the PSU will still power up for few seconds...

Note: The resistor was not burned but i just replaced it with a new one with same value but higher wattage 3W as i have seen in previous posts by other members.. Also replaced 2 caps with higher 681pF 2KV.

Now, nothing has changed. it still powers up for few seconds and shuts down automatically.

What could be the other cause? I am not that expert but i know how to use the solder and little of the multi tester.

Are you testing it with a load?
Some power supplies require a load to run properly...

[rayfloyd170]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

Are you testing it with a load?
Some power supplies require a load to run properly...

i tried testing it with load and also without load by shorting green pin and black pin. both have same results.

[Rainbow]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

This PSU does not need any load. There's even a test button near the power connector so you don't need to short any pins manually.

If the PSU runs only for a moment, check PFC components (D5) and also IC52. But I don't see how IC52 could be damaged as Q51 is OK.

[moula]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

I have the same PSU turns on for about 15sec then switchs off and doesn't turn on unless i unplug it and let it cool off for a bit, so something is definetly getting hot, i've tested all
the caps they all seem fine with low esr both on the main and the secondary side, all the voltages are present when turned on, if someone ever encountred this problem your help will be much appreciated.

[rayfloyd170]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

I have the same PSU turns on for about 15sec then switchs off and doesn't turn on unless i unplug it and let it cool off for a bit, so something is definetly getting hot, i've tested all
the caps they all seem fine with low esr both on the main and the secondary side, all the voltages are present when turned on, if someone ever encountred this problem your help will be much appreciated.

how did you solve your issue? i just happen to bring back this old psu from my closet and tried it with my psu tester. It still powers on for 5-10 seconds with correct voltages and suddenly off. I removed the PFC board and saw one diode (D303) shorted. i replaced it but still the same issue. it powers up for few seconds. i dont know if i can use it without the PFC baord attached.

what could be the other causes?

[lotas]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

It looks like a problem with the chip burned 5 pin.

[rayfloyd170]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

It looks like a problem with the chip burned 5 pin.

Hi, actually i am just grabbing the photo from here and encircled in red the diode that was shorted. All other parts are physically in good condition. i successfully replaced the diode but still with the same problem.

I was thinking it has to be something related to over/under protection sort of thing because it powers up with good voltages for a few seconds only and autoshut off and after that i have to wait for a moment before i can power it again for few seconds.

[abhishekkumar1902]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

Beware, most CP012A on eBay or AliExpress are fake. Before using any of them, check voltage drop from GND (pin 5) to all other pins using a diode test on a multimeter. If any is missing or over 1000mV, the chip is fake.

Luckily, the CP012A is only a remarked NCP1252A. Verified.

I've fixed many of these PSUs. List of usually bad parts:

F1 (F6.3A/250V)
C52 (681K/1KV = 680pF)
Q51 (STW12NK90Z)
R25 (0R27 or 0R2 fusible)

DB1 (GBU606)
D53 (D1 = 1N4148W SOD-123F)
R55 (22R SMD 1206 1%)
C51, IC52 (Cosmo 357NT C = KPC357NT0C (CTR=200-400% VCEO=80V) or 357T)
R36 (4R7 SMD 1206)

sub-board:
IC301 (CP012A = NCP1252A)
J306 (0R SMD 1206)
R304 (2K2 SMD 0805 1%)
Q301 (1P = MMBT2222A)
if R302/R310 showing bad values, replace Q301
D301, D306 (D1 = 1N4148W SOD-123F)
if R329 (4K3) shows bad value (not around 4K25), replace IC51
if R327 (220R) shows bad value, replace Q304 (KSP2222A)
IC302 (UCC28019A - PFC)

Wow this is a great help to quickly check the burnt components. As always the main MOSFET Q51, F1 , R25, C52, IC301, etc were burnt in my unit. Though I am yet to replace them, but is there any quick way of checking the PFC chip IC302 (UCC28019A)? I am observing a low impedance of around 4 to 7 ohms between its VCC and GND pin, not sure if has also gone defunct, any suggestions to passively test it though the PFC MOSFET is totally fine and not shorted.

[momaka]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

Wow this is a great help to quickly check the burnt components. As always the main MOSFET Q51, F1 , R25, C52, IC301, etc were burnt in my unit. Though I am yet to replace them, but is there any quick way of checking the PFC chip IC302 (UCC28019A)? I am observing a low impedance of around 4 to 7 ohms between its VCC and GND pin, not sure if has also gone defunct, any suggestions to passively test it though the PFC MOSFET is totally fine and not shorted.

If you don't want to remove the entire chip, then just isolate its Vcc pin by removing whatever components connect to it that may be allowing a low-resistance path to exist. In all likelyhood, though, either the chip is bad or the components that generate the Vcc supply to the chip are bad.

[abhishekkumar1902]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

If you don't want to remove the entire chip, then just isolate its Vcc pin by removing whatever components connect to it that may be allowing a low-resistance path to exist. In all likelyhood, though, either the chip is bad or the components that generate the Vcc supply to the chip are bad.

Thanks, I removed the chip itself yesterday and found that the short resolved post that. It is surprising to see that the main switching MOSFET+Switcher IC also blew this PFC chip, interestingly the PFC mosfet is not shorted at all.

Pretty sure the SMPS will be back to life when I replace the blown main switcher mosfet and switcher IC, but can the supply work without the PFC chip (circuit) in place. I know its efficiency and PFC correction will go away, but is it to okay to use this supply without PFC? ��

Also, any idea if there are alternatives to the UCC28019A PFC chip in the same pin package that I can easily drop?, else yes I need to order that separately from a chip supplier.

[stj]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

look on the underside of the main board - usually some smd resistors get burned

[momaka]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

Pretty sure the SMPS will be back to life when I replace the blown main switcher mosfet and switcher IC, but can the supply work without the PFC chip (circuit) in place. I know its efficiency and PFC correction will go away, but is it to okay to use this supply without PFC?

Maybe.

It will depend on a lot of things.

For starters, the APFC circuit boosts the voltage to around 370-390V DC (or sometimes more) on the primary cap. With 220V AC mains, you will probably only get around 330-340V DC on the primary cap. Small difference, but may be enough to impact the usable power output considerably. In my case, I tested this with an Enermax Pro 82+ EPR525AWT (525 Watt ATX PSU) and was only able to get about 150-200 Watts of power output from the PSU before it started shutting down. The PSU still had good efficiency, but just couldn't pump out anywhere near its full rated power because of the disabled APFC circuit. Full details how I modified the PSU in this thread:
https://www.badcaps.net/forum/showth...211#post854211

In the case of my Enermax Pro 82+ EPR525AWT, since it has a CM6802 IC (APFC + main PS PWM combo), all I had to do was "trick" the APFC voltage feedback circuit into thinking the primary side was at proper 370-380V DC, when in fact it wasn't. But for this Dell H240AS PSU, I'm not sure what you would have to do to use it without the APFC circuit. You may not have to do anything at all - possibly just disable the APFC MOSFET(s) (by grounding their Gate pins to primary ground) or remove them entirely. But if there is some voltage detection circuit that reports back to the main PWM IC that the voltage on the primary is low, then you might have to do something similar to what I did with my CM6802 IC. I've never come across these H240AS PSUs on my bench, so unfortunately I cannot provide more details what else might be involved. Of course, it is worth a try. That way, at least with a low load, you can check if the rest of the PSU may be OK (provided that it works.) That said, I strongly suggest using a 100-300 Watt halogen lamp in series with the AC line going into the PSU. This way, if there is something else wrong with the primary side, at least you won't blow up more components. Generally speaking, for the APFC IC to blow up, that means something else must have gone quite wrong.

For starters, check the 5VSB circuit first - make sure the PSU is outputting both 5V standby on the output, as well as a stable and clean primary auxiliary supply (probably 10-20V.) If these are good, then you may proceed further with the PSU, whether that is testing it without the APFC IC or replacing everything and hoping that it works. Like stj mentioned, check all of the small SMD caps and resistors underneath the PSU to make sure nothing else is burned.

[abhishekkumar1902]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

Maybe.

It will depend on a lot of things.

For starters, the APFC circuit boosts the voltage to around 370-390V DC (or sometimes more) on the primary cap. With 220V AC mains, you will probably only get around 330-340V DC on the primary cap. Small difference, but may be enough to impact the usable power output considerably. In my case, I tested this with an Enermax Pro 82+ EPR525AWT (525 Watt ATX PSU) and was only able to get about 150-200 Watts of power output from the PSU before it started shutting down. The PSU still had good efficiency, but just couldn't pump out anywhere near its full rated power because of the disabled APFC circuit. Full details how I modified the PSU in this thread:
https://www.badcaps.net/forum/showth...211#post854211


In the case of my Enermax Pro 82+ EPR525AWT, since it has a CM6802 IC (APFC + main PS PWM combo), all I had to do was "trick" the APFC voltage feedback circuit into thinking the primary side was at proper 370-380V DC, when in fact it wasn't. But for this Dell H240AS PSU, I'm not sure what you would have to do to use it without the APFC circuit. You may not have to do anything at all - possibly just disable the APFC MOSFET(s) (by grounding their Gate pins to primary ground) or remove them entirely. But if there is some voltage detection circuit that reports back to the main PWM IC that the voltage on the primary is low, then you might have to do something similar to what I did with my CM6802 IC. I've never come across these H240AS PSUs on my bench, so unfortunately I cannot provide more details what else might be involved. Of course, it is worth a try. That way, at least with a low load, you can check if the rest of the PSU may be OK (provided that it works.) That said, I strongly suggest using a 100-300 Watt halogen lamp in series with the AC line going into the PSU. This way, if there is something else wrong with the primary side, at least you won't blow up more components. Generally speaking, for the APFC IC to blow up, that means something else must have gone quite wrong.

For starters, check the 5VSB circuit first - make sure the PSU is outputting both 5V standby on the output, as well as a stable and clean primary auxiliary supply (probably 10-20V.) If these are good, then you may proceed further with the PSU, whether that is testing it without the APFC IC or replacing everything and hoping that it works. Like stj mentioned, check all of the small SMD caps and resistors underneath the PSU to make sure nothing else is burned.

Thanks for giving your valuable time to the query ������

I totally got you, and I think is a good learning point to see how Active PFC works in SMPS design. I will go through the UCC2819A datasheet and relatively check the design of this H240AS SPMS to understand it. I have also ordered few pieces of UCC28019A already to fix it.

And yes, I do use a 200w, 230V AC halogen in series on the mains to test these blown-out SMPS supplies for a probable short. Mains MOSFET and blown PWM chip usually also blows a few more components on the protection and bias circuit especially the gate drive circuit, fuses, etc so yes, I will be replacing all that along with the main mosfet and switcher IC.

Per your advice, I will also meanwhile check for the APFC feedback (390v boosted voltage sensing) to the main switcher circuit. I didn't know that, it is a good advice.

I will let you know how I fixed it and what I found later on in the process of fixing it. Just for learning, I will also test, how it behaves without the APFC circuit and if the output gets derated or not.

Once again, thank you so much for your valuable inputs sir.

[accord89]

Re: DELL OEM H240AS-00 (HIPRO) ~ major blow up!

If you don't want to remove the entire chip, then just isolate its Vcc pin by removing whatever components connect to it that may be allowing a low-resistance path to exist. In all likelyhood, though, either the chip is bad or the components that generate the Vcc supply to the chip are bad.

can you help me how to measure with volt meter if this IC302 is good or not?

How to check this?

My IC301 was burned and i replace it with NCP1252

But the power supply does not power on. I replace and check all the components that are written on this topic.