1250W XFX PFC power supply refuses to start up. No clue! - Page 1
Forum section: electronics / general

author: xtv
author_rank: Contributor
timestamp: January 23, 2014, 07:17:59 pm
content: Straight to the point:- Was working before. Refused to start back after a software shutdown.- Strange oil on the back of the pcb. No appearently leaking cap around this area.[Heard the thermal pads on the case contains oil in its formula and can release it over high temps]- No smoke, no smell or visually toasted component- Diode and big FETs in the left side of the pcb seems okAre OK.- Standby 5VCC is working- Right after switching the main power on, the big caps voltage is 170v.- After attempting to switch the psu on (green-black jumper), the big caps voltage peaks to 400v, but start discharging (slowly), until it reaches back to 170v.- The relay never switches on.- No output on 12V, 5V or 3.3v supply- I've also measued the VCC / GND of the "protection" IC PS232F in the right side of the PSU, and it gets 5v. Probably most control components are being powered.- PWR_OK (or Power Ready) pin in the ATX connector have near to zero vcc- PS_ON (Green wire) Atx pin have +3.2v- No noise that I can notice. (usually, switching PS does a small high pitch noise)- NiHaoMike suggested his ninja technique to turn a AM/SW radio next to the PSU and attempt to switch it on. We were able to hear it oscillating when the mains switch is turned on. Also a peak noise when attempting to power it onRecord is in here:http://oztix.sdf.org/xfxpwr/PSU_startup_SWRadio_5700KHz.mp3- peter.mitchell suggested to forcibly power the 12v rails of this PSU using an external regulated PSU using a low value resistor in series to check a possible short and if the DC-DC conversion circuit works. I've got this PSU to work doing the following: (1) Powering it. (2) Power the 12v rail using the external PSU. (3) Ground PS_ON. The relay closes here. (4) Remove Aux. PSU. All outputs working: 12v; 5v; 3.3v.--------------------------------------Hi everyone. I'm from Brazil and I have spent the money I had on a litecoin mining rig about 1 and half months ago. Turns out that, after this time running, the XFX 1250W Pro Black Edition PFC power supply is not starting anymore. Not even hard gounding the green wire of the ATX connector. As computer equipment is around 40% cheaper in Paraguay, I've bougth everything there. So rma would be a problem, but I didn't expect having problems so early!This happened after a soft windows shutdown. When I tryed to start the machine again, nothing happened. No smoke, no noise. So I decided to open the case, in hope to find a leaking capacitor, toasted transistor or diode, check the fuse, and so.I found nothing visually strange, except of some components in the back of the board soaking on oil. These components are pressed by a thermal conductive rubber that is fixed in the botton plate of the case.I'm wondering if this is commonly used to help thermal conduction from the components to the backplate (this area gets real hot while working)I have checked every electrolytic capacitor over this region to make sure it wasn't a leaking cap. All of them not only looks good, but also show correct values in a capacimeter.This looks an advanced PFC power supply, and I have no good idea on what and where to start investigating.Any help on diagnosing this will be much appreciated!The leakage in the back plate is barely seen in eye, but the camera seems to capture it quite well..The rubber is already clean in the picture, but was a pool of oil when I opened it.

author: mariush
author_rank: Super Contributor
timestamp: January 23, 2014, 07:45:47 pm
content: This is a Seasonic OEM design. Quite a high quality one.The main transformer looks like it was overheated (i see something that looks like melted plastic). I would check the main transformer to see if it didn't have its fuse popped due to heat.The relay is (if i remember correctly) there to disable the 5v standby section and switch it to the main dc-dc 5v converter once the power supply runs, to increase the efficiency (the separate 5v standby is less efficient than generating 12v and then getting 5v using dc-dc converter). Or it could be just disconnecting the main power supply and leaving just the 5v standby when working, again for efficiency numbers (to have less losses when turned off)

author: xtv
author_rank: Contributor
timestamp: January 23, 2014, 09:25:27 pm
content: Hey Mariush, thanks for having a look.If you mean the white thing over the transformer coil, looking like melted plastic, it's a volume glue used to fixate components. It's used all around the pcb.If you mean by the resine drop over it, yeah I may agree with you. Although I belive it would have some smell if it was overheated that way, and it hasn't, at all.I don't know these transformers used in ATX PSUs very well, but the coils are not open (my hand multimeter says zero ohm between terminals, not sure how low that should be), but primary and secondary are isolated. Are these fuses internal?BTW, I've misinformed something above. PWR_OK are not +5VCC. It's near zero under mV scale. The one with 5VCC is the purple wire, that is the standby voltage (VSB). Correcting it...

author: SeanB
author_rank: Super Contributor
timestamp: January 24, 2014, 04:25:23 am
content: No standby 5V means U1 is dead, and it looks like it has popped it's top as well. When replacing it change the small capacitor next to it as well, as that could be the cause along with a dry joint on the transformer, or a period of high mains voltage. It could have happened a while ago but you will only see it on power off after the main power rails go away.

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 24, 2014, 12:06:49 pm
content: I haven't gone through anything in your post or the posts above, however, i do congratulate you for providing one of the most informative and best picture taken posts on this forum relating to a problem in the last 2 years. Thank you, this post should be an example to others.

author: xtv
author_rank: Contributor
timestamp: January 24, 2014, 04:04:19 pm
content: Quote from: SeanB on January 24, 2014, 04:25:23 amHey Sean, thanks for having a look.Actually, Standby is 5VCC. What is not (and should be) is Power_OK (or Power Ready), which tells the motherboard the PSU is ready to power up and everything is ok.The little mark over the U1 that made you think it's popped is a ink pen. I've visually inspected it and it seems ok.Also, PS_ON (the pin that switches the PSU on when "lowed") is at 3.2v, what makes me think the circuit that controls the PSU startup may be working, but something is wrong to start delivering power..

author: xtv
author_rank: Contributor
timestamp: January 24, 2014, 04:28:31 pm
content: Quote from: peter.mitchell on January 24, 2014, 12:06:49 pmThanks a lot, Peter.I belive if you're taking somebody else's time, you should at least give the best to help them help you.Also this PSU costs 1k bucks in my country.. So my options are to fix it, or fix it. Or keep trying...

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 24, 2014, 04:54:51 pm
content: Set an AM radio next to the PSU, turn it on and tune it to a blank station, then do the green to black jumper. Let us know what you hear since that can give a hint if it the PSU is attempting to start up at all.

author: Monkeh
author_rank: Super Contributor
timestamp: January 24, 2014, 06:57:36 pm
content: Quote from: xtv on January 24, 2014, 04:04:19 pmNo, it tells the motherboard when the PSU is turned on properly, not that it's ready to. It should remain low when the PSU is on standby.

author: Monkeh
author_rank: Super Contributor
timestamp: January 24, 2014, 07:12:58 pm
content: The relay turns on the main supply. Pull the relay and test it, then start investigating the circuit controlling it.

author: Monkeh
author_rank: Super Contributor
timestamp: January 24, 2014, 07:59:29 pm
content: Quote from: AcHmed99 on January 24, 2014, 07:41:12 pmI think you'll find that's a fuse. Notice the gigantic inductor for inrush limiting.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 24, 2014, 08:03:43 pm
content: The PTC that gets bypassed is that heatshrinked green bit next to the relay.

author: Rerouter
author_rank: Super Contributor
timestamp: January 24, 2014, 08:39:43 pm
content: The capacitor next to U1 has leaked, and flowed over the edge, that is the residue you see in the image of the casing, the increase in ESR and drop in capacitance probably then caused U1 to oscillate and pop, replace it and the chip, though you may have to find the datasheet on the cap as these things can get upset by changes in capacitance and ESRif you can find more info on the cap, replacing it with a higher voltage model with similar ESR and the same capacitance would be the best bet,

author: Monkeh
author_rank: Super Contributor
timestamp: January 24, 2014, 10:06:28 pm
content: Does the relay close?

author: xtv
author_rank: Contributor
timestamp: January 24, 2014, 11:21:25 pm
content: Quote from: Monkeh on January 24, 2014, 10:06:28 pmThe relay never closes.I've monitored the standby 5v while attempting to switch the psu on, to check if the voltage drops. Not even a little.

author: Monkeh
author_rank: Super Contributor
timestamp: January 24, 2014, 11:39:59 pm
content: Quote from: xtv on January 24, 2014, 11:21:25 pmNow, check if the relay works and/or if it attempts to energise it.

author: xtv
author_rank: Contributor
timestamp: January 24, 2014, 11:50:24 pm
content: Quote from: Rerouter on January 24, 2014, 08:39:43 pmWhat an eagle's eyes, uh?Actually, that cap leak you see going to the edge (with dust over it), is a minor part I haven't cleaned.The big region with a leak was this one:http://oztix.sdf.org/xfxpwr/region_oil.jpgMy main suspicion was the bigger cap in the center of the smudge.As I reported, the MOSFETS on the back of the board was submerged in some sort of oil. I've asked here if that was used to help dissipate heat.IF that oil is meant to be there, a small soldering fail of those heat sinks left a hole open in the pcb, allowing the oil to submerge to the surface of the board.I've searched internal pictures of this PSU in the Internet, and I haven't seen this sort of oil in any of those. Reviewers never commented anything about oil in the back of the board.But again, I have removed those electrolytic capacitors in this region, none have any signal of leaking, neither shows abnormal capacitance in a LRC meter. (Wish I had a scope to check the charge/discharge curve)I tryed to measure the resistance of this oil (maybe it's stupid) but, it seems unconductive. At 2 Megaohms, less than half millimeter one probe from another, no signal of any resistance. I don't know if the liquid inside an electrolytic capacitor is conductive, but I wanted to check if that could have caused damage to the mosfets..These fets in the back of the board are wired in parallel (S-D). I haven't removed them to test individually, but none of them are shorted.Now that "solid state caps", can't have leaked?

author: Monkeh
author_rank: Super Contributor
timestamp: January 25, 2014, 12:01:18 am
content: No, the oil won't have been anything to do with the FETs, and no, solid caps can't leak (the clue is in the name). It's come out of one of the wet electrolytics somewhere, unless it's some byproduct of a defective silpad.

author: xtv
author_rank: Contributor
timestamp: January 25, 2014, 12:12:12 am
content: Quote from: Monkeh on January 24, 2014, 11:39:59 pmOh, I guess we have some progress.The relay (component) works. 9v dc arms it gracefully.On a switching on attempt, it's voltage peaks from 0v to 5v, and comes back to 0v. (I was able to hear a little "click" inside this time. It's trying to arm, but it wont.I'll take a look at the relay driver transistor, but if it was bad, there was no reason to fall back to zero, right?

author: xtv
author_rank: Contributor
timestamp: January 25, 2014, 01:22:07 am
content: Quote from: Rerouter on January 24, 2014, 08:39:43 pmI've removed and tested the cap you mentioned.unfortunately, it looks ok..http://oztix.sdf.org/xfxpwr/47ucap.jpghttp://oztix.sdf.org/xfxpwr/47ucap2.jpghttp://oztix.sdf.org/xfxpwr/47ucap3.jpg

author: Psi
author_rank: Super Contributor
timestamp: January 25, 2014, 01:27:38 am
content: I've not read this thread, so if this has already been said sorry, but might be a good idea to locate the bootstrap resistor and check that.It's usually like 100K or above and will be throughhole. If it looks to have got hot at all, remove and check it.It wont start up with that resistor failed open. It's required to bootstrap the flyback and it's a common failure mode due to being underspec'ed most of the time.(although i wouldn't expect that in a good quality psu)

author: xtv
author_rank: Contributor
timestamp: January 26, 2014, 06:29:51 am
content: Quote from: AcHmed99 on January 24, 2014, 07:41:12 pmThanks, AcHmed.You're right about the relay, it just shorts the thermistor. It's driver is feeded by a zener; when the voltage at C209 (the brown cap near U1) rises, the relay bypasses the PTC.About the bias supply, aint it the same supply as 5V standby? I'm getting +5Vcc in ATX 5V standby.I belive most controlling circuit is up, because I can hear the oscilation noise in a shortwave radio near the PSU. A peak noise while attempting to power it on as well. (audio file's in the main thread)I've mailed Seasonic tech support sharing this thread. Let's see if they can be helpful in some way...

author: crmaris
author_rank: Contributor
timestamp: January 26, 2014, 07:50:31 pm
content: The relay is only to bypass the NTC thermistor and allow it to cool it down for the next restart (and save some energy lost on it).Firstly you have to be extra carefull while you apply power to this unit since the current on the first side is dangerous! That said do the following.Connect it to power and switch on the on/off switch. Then short the green and black and check if the relay activates (it will make a sound). If it does then measure the voltage on the large APFC caps. It should be 380 VDC (DC bus voltage of the APFC converter). If it isn't so high then you have a problem although some PFC controllers can drop it down to 320 VDC when there is no load applied, to increase efficiency.If the DC bus voltage is ok then the problem is either in the secondary side or to the main switchers/transformers so things get more complicated and I cannot do a diagnosis from here.From what I know some batches of this unit showed similar problems but with a specific procedure you were able to start them again (this had to do with the on/off switch but I don't remember how). A user had reached me again with a similar problem but what ever he did he couldn't make the PSU operational again so I think you should try, before you open it, your luck with XFX's RMA (which isn't from the good ones as I hear, at least here in the EU).However Seasonic's RMA is top so better next time buy directly the Seasonic unit (X-1250), although it might be a little more expensive.

author: xtv
author_rank: Contributor
timestamp: January 27, 2014, 12:19:26 am
content: Quote from: crmaris on January 26, 2014, 07:50:31 pmHello crmaris, thanks a lot for having a look.Here are the results:- Right after switching the main power on, the big caps voltage is 170v.- After attempting to switch the psu on (green-black jumper), the big caps voltage peaks to 400v, but start discharging (slowly), until it reaches back to 170v.The relay never switches on.I've also measued the VCC / GND of the protection" IC PS232F in the right side of the PSU, and it gets 5v.Quote from: crmaris on January 26, 2014, 07:50:31 pmThat's true, this psu since the beginnig had some problems powering on.. I had to switch it off and on, wait at least about 30 seconds and push the power button (case) for it to turn on. Now you made me wonder if this could be a capacitor that was operating right in the limit and now that it got worse, wont start at all...

author: xtv
author_rank: Contributor
timestamp: January 27, 2014, 03:48:27 am
content: Quote from: Psi on January 25, 2014, 01:27:38 amHi Psi, thanks for the suggestion.I've checked every resistor in the pcb (without desoldering them), except in the PFC / PWM small pcbs.Do you have an idea how can I locate this resistor?

author: crmaris
author_rank: Contributor
timestamp: January 27, 2014, 06:14:59 am
content: so you had this problem from the beginning.. Yeap this was the procedure the other guy followed to power it on.If the relay doesn't open at all then the problem must be in the primary. Check the bridge rectifiers if they are ok. Sorry I don't have any other suggestions.

author: oldway
author_rank: Super Contributor
timestamp: January 27, 2014, 08:12:29 am
content: The chance to find a fault in such a sophisticated supply without diagrams is almost zero.You should try to obtain the schematics.Reverse engineering seems very difficult to do because of the high density of components.What is the normal start sequence?1) preload of the electrolytic capacitor with surge current limitation. (normally by fixed power resistor and not a NTC)2) bypass off the resistance by the relay and start of PFC3) as soon as the voltage reaches 390 to 400V dc, converter would start immediately.If dc/dc converter don't start, then relay and PFC are disable.That's what seems to happen.Now, you will have to answer to this question: why dc/dc converter don't start ?For further investigations, you should have a scope and feed the power supply with an isolation transformer for security.What for PWM controller is used in the dc/dc converter?

author: xtv
author_rank: Contributor
timestamp: January 27, 2014, 04:15:28 pm
content: Quote from: crmaris on January 27, 2014, 06:14:59 amWell, yeah, not sure if this is related to the definitive problem I have now.. Before i just had to wait like 30 seconds after powering the mains before switching the unit on. After that, it just worked fine.But now, I can't get this working at all.Quote from: crmaris on January 27, 2014, 06:14:59 amActually, the relay never closes (current keeps flowing through the varistor).That's fine! Thanks for the suggestions, they made me progress a lot.

author: xtv
author_rank: Contributor
timestamp: January 27, 2014, 10:49:43 pm
content: Quote from: oldway on January 27, 2014, 08:12:29 amHello oldway, thanks for the whole info.I think so, wont be easy, but I have no idea on where to get the diagram for this PSU. Do you?It is, quite complex. I've got to understand a little after spending several hours over this PCB.Quote from: oldway on January 27, 2014, 08:12:29 am1) Not sure, but there are two R030 ohm resistors (R201 and R202) in the backside of the board right after the AC rectifiers.http://oztix.sdf.org/xfxpwr/08_Backside.jpgNow, as the big capacitors are getting powered, (and reaching 400v) I assume the FETS that feeds power to it are working.And 170v is just the AC IN being rectified, right? (120 * squareroot(2))2) Now I'm not sure any resistance is getting bypassed by the relay. I just can see the thermistor being passed by.3) Do you know how this is done? what components are used to detect this voltage limit and switch the PSU on?I'm sorry to ask, I have no knowledge on switching power supplies, but what is this DC/DC converter for? Are we talking about primary here? (before the main transformer?)The PWM controller is a CM6901http://www.championmicro.com.tw/datasheet/Analog%20Device/CM6901.pdfhttp://www.techpowerup.com/reviews/XFX/P1-1250-BEFX/images/in_CM6901.jpg(Picture from the TechPowerUP Review that our friend crmaris here did. There are some details about this psu there:http://www.techpowerup.com/reviews/XFX/P1-1250-BEFX/4.htmlThe PFC controller appears to be NCP1654http://www.onsemi.com/pub_link/Collateral/NCP1654-D.PDFHere's the pfc board that is soldered in the main PSU's PCB:http://oztix.sdf.org/xfxpwr/20_pfc_board.jpgQuote from: oldway on January 27, 2014, 08:12:29 amThat's a good point. Thanks for bringing it on. I don't have a scope here (yet), but what about connecting a speaker with a very high impedance resistor in series, to the transformer primary terminals on the pcb? Is the switching frequency low enough to be able to hear?BTW, did you hear the record I made with a shortwave radio near this PSU?

author: oldway
author_rank: Super Contributor
timestamp: January 28, 2014, 10:29:32 am
content: QuoteTry to send mails to support of Seasonic Taiwan, USA and EU asking for schematics and service manual.support@seasonic.com.twusa@seasonic.comsupport@seasoniceu.comYou could also try to send a mail to:japan@seasonic.comQuoteProbably used as shunt for current information for PFC current limitation.The "big capacitor" is first charged from the rectified mains voltage (180V from 130Vac or 320V from 230Vac mains voltages).When PFC start, voltage on the capacitor raises to 390/400V.If design is correct, PFC can't start if the relay is not on. (bypass of the CTN)QuoteIt could be done using de min startup voltage of the CM6901 (Startup Vcc (pin5) greater than 10.8V -Vcc must be between 11 and 20V), or some "inhibit" logic control from PFC.No way to "guess" how it works, it's too sofisticated and too complex.Switching frequency is for sure far above 100Khz.It's not an audio frequency (20 to 20Khz)

author: diyaudio
author_rank: Frequent Contributor
timestamp: January 29, 2014, 03:51:52 pm
content: Quote from: xtv on January 23, 2014, 07:17:59 pmHi not sure if you debugged the problem. I would start here.http://www.rom.by/files/apw7159a_0.pdfDebug all the node(s) with a scope and multimeter around the this controller IC and assert against the datasheet (notably the shut down, reference supply and error amplifiers) you should be able to reverse engineer the design as it layout is modular. its a good power supply. Some some precaution and make sure you don't probe the HV DC Bus with scope please unless you know what you doing.According to the the datasheet quote.The APW7159A is a dual channel voltage mode and syn-chronous PWM controller which drives dual N-channelMOSFETs. The two channels are operated with 180 de-gree phase shift.The device integrates all of the control, monitoring, andprotecting functions into a single package; provides twocontrolled power output with over-voltage, over-temperature, and over-current protections.The APW7159A provides excellent regulation for outputload variation. The internal 1.0V temperature-compen-sated reference voltage provides high accuracy of 0.8%over line and temperature. The device includes a 50kHzfree-running triangle-wave oscillator that is adjustablefrom 50kHz to 400kHz.The APW7159A has been equipped with excellent pro-tection functions: POR, OCP, UVP, and OVP protections.The Power-On-Reset (POR) circuit can monitor the VCCand OCSET voltage to make sure the supply voltage ex-ceeds their threshold voltage while the controller isrunning. The Over-Current Protection (OCP) monitors theoutput current by using the voltage drop across the highside MOSFET’s RDS(ON)When the output current reachesthe trip point, the controller will be latched. Under-VoltageProtection (UVP) and Over-Voltage Protection (OVP) moni-tor the FB voltage to protect APW7159A from burnout whenoutput voltage is under 50% or over 120% of normal out-put voltage. The APW7159A is available in SOP-20package.

author: xtv
author_rank: Contributor
timestamp: January 30, 2014, 02:21:43 am
content: Quote from: oldway on January 28, 2014, 10:29:32 amThanks for being so helpful.You're right, Im trying to get the schematics for this psu..I have also found out that there are several people having the exact same behaviour with this and the Seasonic X series (which are the same PSU).Let's see if Seasonic have some info to provide for the community.Meanwhile I'll be doing some tests when I have some new idea.If you have too, please tell me and I'll do it.

author: xtv
author_rank: Contributor
timestamp: January 30, 2014, 02:26:17 am
content: Quote from: diyaudio on January 29, 2014, 03:51:52 pmHi, thanks for the info.I haven't found the issue in this PSU yet.I wasn't giving much importance to this IC, as it's main function is DC-DC conversion (from main 12v to 5v and 3.3v). But now that you mentioned it has such protections, it my be disabling the main switching circuit by detecting (or misdetecting) some abnormal condition.I'll have alook at it and post the info here.

author: bitshape
author_rank: Contributor
timestamp: January 30, 2014, 05:04:10 pm
content: Have you checked the 2 yellow X2 Film-Capacitors at the input for Capacitance?Once I've encountered a troublesome PSU where one of them was at 1/10th of the original Capacity.

author: mariush
author_rank: Super Contributor
timestamp: January 30, 2014, 05:32:31 pm
content: Those yellow x2 capacitors are just for noise/emi filtering, wouldn't affect the psu even if they were missing.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 31, 2014, 02:05:50 am
content: Quote from: mariush on January 30, 2014, 05:32:31 pmI have seen a design that used a X2 cap to supply the initial startup voltage, but every modern PSU I have looked at handled the startup inside the standby switcher and it's not relevant to this problem since the standby rail comes up just fine.What could happen is a load side X2 cap failing and destabilizing the PFC due to increased input impedance, but it's unlikely.Does the 12V rail even try to come up on starting the PSU? What about the 5V and 3.3V?

author: xtv
author_rank: Contributor
timestamp: January 31, 2014, 04:29:13 am
content: Quote from: NiHaoMike on January 31, 2014, 02:05:50 amNo. I've put a led to monitore the 12v rail, never catched anything with it. (I'll check it better if any signal comes from 12v with a multimeter during the startup attempt).5v and 3.3v outputs are generated using the 12v rail by a dc-dc converter in the modular connectors board (IC APW7159, mosfets and inductors in there). So no 12v, no 5v or 3.3 either.BTW, as I suspected, Seasonic won't provide the electrical schematic. They promised a solution though, let's see what comes out..

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 31, 2014, 11:54:29 pm
content: Check for shorts from the rails to ground.

author: xtv
author_rank: Contributor
timestamp: February 21, 2014, 10:37:15 pm
content: Quote from: NiHaoMike on January 31, 2014, 11:54:29 pmNo shorts from the outputs to ground (not on 12v, not on 3.3 neither 5v).An update on this thread after awhile;A friend in this forum suggested me to check the PS232F** monitoring ic, saying that some PSUs had a fault on this component.**http://pdf1.alldatasheet.com/datasheet-pdf/view/307256/SITI/PS232F.htmlThis IC checks the PSU outputs for over/under voltage and offers over current protection. It also provides a front end for the PWR_ON atx pin and PWR_OK output signal.As far as I could understand of this short datasheet, it countains two outputs:- PowerGoodOutput (PGO, pin20) which goes to the ATX cable, informing the motherboard the PSU is providing acceptable outputs;- Inverted Fault Protection Output (FPO, pin 3) which I'm not sure, but seems to enable the primary side (signal goes through an opto-isolator).Both pins are kept high (+5v) through a 1k resistor connecting to the 5v line.PGO is powered by 5v output, and as the PSU isn't starting, it keeps at 0v.State for this pin is: HIGH=Power is OK. LOW=ProblemsFPO in the other hand uses the 5v STB line to get stated HIGH.State for this pin is HIGH=Disable Primary LOW=EnableNow, I've monitored this PGO out, and as I try to switch the PSU on, it quickly falls to LOW, then comes to back to HIGH again.I can't tell exactly how long this takes, but it's quite fast, almost unnoticable in the multimeter. And this is a guess, but I presume that this short time probably wouldn't be enough to load the caps in the secondary that PS232F could evaluate anything (at least on over/under voltages).As another test, I've disconnected the PS232F FPO pin, and in place "grounded" the signal using a 100R resistor.In the shortwave radio, (my audio oscope), I could notice while I was grounding this pin, the PSU was oscillating in a different frequency..Still, the 12V rail passed slowly from 0v to 5mv.when interruped, it didn't fall back to 0v. it kept at 5mv.I would suspect of a bad transformer. But this would be quite against the fact that the PSU was running just fine, was shut down properly and refused to start back...Any suggestions are welcome.PS: I was obcessed looking for a leaking cap in this PSU. took almost every electrolytic cap out and tested. No leaks, no strange value. I was told then this thermal pad could have oil in its formulation and could release it when heated up.

author: peter.mitchell
author_rank: Super Contributor
timestamp: February 22, 2014, 12:57:49 pm
content: Some low tech testing;Got an isolated 12v 1a~ power supply? A wall wart will do, provided it is isolated/floating.Get say... 5 100ohm through hole resistors and twist them together in parallel for a 20 ohm resistor (or if you have a spare 20ohm 1w resistor, it will do too).Put it in series with the positive wire from the 12V psu, just strip some wire and twist it together. Strip a little off the end of the ground wire (maybe 3/16th inch~5,mm) and fold it over the cable.Get one of the modular 5.25" peripheral power cables (kind you use for dvd drives and older hdds, often called "molex connectors"), plug it into the back of the psu, stick the ground wire into the ground pin on the plug (one of the two middle ones, it should fit nice and snug folded over itself), then put the other end of the resistor into the 12V rail of the PSU it should fit in reasonably snug, or at least not fall out too easily.With your multimeter handy, stick your probes into the other connector on the cable so you can watch the voltage.Plug the wall wart in and keep your eye on the meter as you flick on the wall wart/12v power supply, see if the 12 rail rises up quickly to 12v, or stays low.If it stays low (0-5v) for more than 10~ secs, turn off the wall wart - you probably have a short on the 12v rail.If it rises up to somewhere near 12v (say 9-12~v), cautiously feel the resistor(s) to see if they are hot, if they are "warm" its OK, if they are smoking or getting VERY hot its not Ok.If it gets Very hot, eg, would burn you if you touched, turn off and wait for it to cool down, while waiting, carefully feel around the PSU to see if there is any warm/hot areas, these may not be full "shorts" but enough to not get the 12V rail up in time to trigger the UVP. When the resistor cools again do the same until you find the component. If you don't find the component, check the voltages of the 5v and 3v3 rails.If it doesn't get hot and the 12v rail is 9-12v, plug the pc power supply into the wall and short the green pin to ground, does the PSU start up? If it starts up, unplug the wall wart and see if it stays running.sorry to end abruptly but im off to bed, work in the morning. Good luck!

author: xtv
author_rank: Contributor
timestamp: February 24, 2014, 10:22:04 pm
content: Hello Peter,Thanks a lot for the suggestion.Well, you made it. It worked!Here's what I did:As suggested, I used a regulated 12V as an auxiliar power supply. Put a 4R7 20W resistor I had in series (with a 5A fuse just in case), and feeded the PSU's 12V rail.I first started the main (deffective) PSU, let the 5v stb rail come up.Then I powered the auxiliar 12V psu. Somehow, the oscilation noise in the radio just gone (or was drastically reduced).'Til here, no power out of 3.3 or 5v rails.Next, I grounded the green atx wire. In the sequence, the relay turned on, 5V and 3.3V up!Then I disconnected the Aux 12V PSU, and could confirm that the deffective PSU was actually turned on and providing all 12V, 5V and 3.3v outputs.Wondering now what's in between this 12v rail and the power up circuit that could be bad...Have an idea?

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 25, 2014, 02:46:45 am
content: Try putting a load (car light bulbs work great) and see if it can hold it. If so, gently tap the heatsinks and boards with a nonconductive object to see if you can make it stop working. Then unplug it for a few hours and see if it will come back up.

author: peter.mitchell
author_rank: Super Contributor
timestamp: February 26, 2014, 09:49:39 am
content: There is probably a soft start capacitor or the like which sets the delay time for UVP/UVLO during start up , the value used is probably right on edge, combined with tolerances makes it marginal - the 12v rail can't come up quick enough (charge all the capacitors ect) before the delay runs out and the device turns off/does not start.

author: xtv
author_rank: Contributor
timestamp: February 28, 2014, 06:13:27 pm
content: OK, so in search for a bad cap, I have soldered extra caps on the backside of the board in parallel with the onboard ones. At least, using the same capacitance.No success on powering on.Then I started monitoring which caps were getting powered, which were not and which had spikes / pits while attempting to power this PSU on.So here they are:High Res Image Link:http://oztix.sdf.org/xfxpwr/08_Backside_rectif.jpgWhen I power the PSU, Cap A quickly reaches 12v and slowly rises up to 18v.Taking a better look, it's being powered by the small standby transformer, that also delivers 5V STB (and probably 12v on this rail).A Diode labeled T3 (D105) is being used as a rectifyer, which I found to be a BAV21 type (http://www.diodes.com/datasheets/ds30119.pdf)Then, the rail is connected to a 2R2 resistor, and powers the Cap A.When I try to start the PSU, the voltage on Cap B and Cap C peaks, looks like not above 10,5v (I don't have a scope, so unfortunately can't tell for sure, as it's fast) while the voltage on Cap A drops (maybe to 12v, may get below this, but again, not sure).I then powered the 12v output rail using an external auxiliar power source to check Cap B and C. They get 12v.Noting this behaviour, and as D105 diode was under a 2R2 resistor (R115), I soldered a big 4700uF in place of Cap A to check if it could hold the voltage drop and make the PSU start.After powering the PSU again, I've noted that the voltage rises quite slowly after reaching 13v.. and I was only able to make this PSU power by itself* when this cap reached 16,5v. At this voltage it can sustain the load to power the other necessary components.* By "power by itself" I mean, without needing to power the 12v rail using an external PSU. The PSU of course, will only start after grounding the green ATX wire.This led me to suspect Diode D105 wasn't ok (although it's voltage drop was around 0,5v), maybe it's internal resistance somehow raised (if that even exists). So I've soldered a BAV21 diode in parallel with it. No success; same behaviour.Next suspicious componont would be the Q101 transistor, labeled W2T (seems to be a PMBT4403) (http://pdf1.alldatasheet.net/datasheet-pdf/view/18686/PHILIPS/PMBT4403.html).It seems to be the driver for Caps B and C, and related circuit.I've removed this Q101 and checked the voltage drop between it's terminals: 652mv B-C and 654mv B-E. Looks reasonable, but I don't know this type of transistor.What is strange though, is that this connection between Cap A and Caps B and C (made by Q101) is in series with a 68R resistor (R118) which I'm guessing is quite high to transfer enought power in such a short time...With that, my guesses are:This section with Caps B and C have somehow lowered it's impedance;Or something is wrong transfering power from Cap A to B and C;Or even something might be wrong with this standby power transformer or its primary side? (Although 5v stb is provided by this same component and have a stable output under reasonably high loads)PS: All Capacitors A, B and C have common ground, which is the same as the outputs ground

author: PedroDaGr8
author_rank: Super Contributor
timestamp: February 28, 2014, 06:32:23 pm
content: I tend to check the resistance of transistors, not the voltage drops. Blown transistors often show low resistance.Sent from my EVO using Tapatalk

author: xtv
author_rank: Contributor
timestamp: February 28, 2014, 08:54:14 pm
content: Well, I've used a BD140 transistor in place of Q101. Also used a 220uF in place of 100uF Cap A. Both helped by auxiliar BAV21 diode in paralel.Same behaviour as with Q101 in place.

author: peter.mitchell
author_rank: Super Contributor
timestamp: March 02, 2014, 06:29:54 am
content: So, just looked at the voltage monitoring chip and it has no soft start caps, but it does have filtering caps on the sense lines, unfortunately because of vias etc i can't clearly see which ones are connected,Do you have any small 0.1-1µf ceramic caps sitting around?Try de-soldering these two caps, here;https://dl.dropboxusercontent.com/u/677635/explanation%20device%2010.pngand if that works, substitute a ceramic between 0.1µf and 1.0µf to replace.

author: xtv
author_rank: Contributor
timestamp: March 22, 2014, 02:52:08 am
content: First of all, I would like to apologize everyone helping me out with this unit.I'm taking long to reply and update the thread for mainly two reasons:- I've being very busy with work these days and- I don't have a proper space for a electronics bench. So, the dinner table turns into my bench from time to time. Problem is, that Ms. gets real mad if things are left there for too long.. You men married or living with a female creature must know what I'm talking about...That makes the time to check something quickly on the psu highly overheaded by setting up and unsetting the whole space...Quote from: peter.mitchell on March 02, 2014, 06:29:54 amPeter, I've checked this caps, both of them measure 0.1uF.No progress replacing them by 0,1uF ceramic ones (I've used 0,1uF because it's the value used on PS232F datasheet example circuit).

author: xtv
author_rank: Contributor
timestamp: March 23, 2014, 03:00:41 am
content: [Solution (provisory)]Got tired of this.I've replaced R118 (68 ohm; backside of the pcb) with a 33R.Also replaced the Capacitor I've refered as "Cap A" in some pictures before, to a higher capacitance one. This cap is the 12v (bootstrap? correct me if I'm wrong) rectifyer.This will of course increase the load over Q101, but the psu is working like a charm.This is not the correct solution, but I'm done with this. Let's see if Q101 will handle it over time.Some points learned / to consider:- Seasonic did replied my emails, but offered no help. People say they have a descent RMA, but technically they offered zero help. Nothing I wasn't expected; they didn't surprised me in a negative but neither in a positive way.Their answer was to contact XFX, which is right, XFX is responsible for the units they label and sell. Didn't lost my time with XFX, they're in the US, would have expensive shipping, long time waiting, and possible problems with the custom house in the way back.- While I was with this psu deffective, I bought a Cougar GX 1050 v2 to replace it. This is a much cheaper (almost half of the price of this XFX), but I had read reviews saying good things about this power supply.I feel in the obligation to report the quality of this Cougar psu here:- It's very well constructed, solid cables, solid connectors, excellent housing, etc.- It runs way, way much cooler than this XFX/Seasonic unit. I'm running 4x high end power hungry video cards, and whether XFX/Seasonic could run it fine, I had the feeling the cooler was at it's top speed, and the exhausting air was hot.This Cougar, although less powerful, seems to handle the same 4 video cards with much less effort, the cooler seems to be at around 50% (makes much less noise) and the exhausted air is just warm. Incredibly how efficient this is.- Another point: to save power, we low the gpu's voltage to the minimum possible, for less heating / wasted energy. This in the other hand has a turn down, the system can freeze with a slightly voltage variation. It is incredible how stable this psu is. I could reach really low voltage values with the system running stable, which turns out requiring even less power from the psu (and cheaper electricity bill).Awesome value!