ATX Power Supply Dead - Page 1
Forum section: electronics / repair

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 20, 2017, 04:45:29 am
content: Working on a power supply. Just can't toss it without completely destroying it first. This PSU has almost no use and is out of warranty of course, so my lessons continue.Upon close-magnified scrutiny of the components nothing indicates failure, i.e. bulging caps, burned FETS, broken wires, fuse, etc.Primary Symptom: When green wire is grounded at main terminal none of the computer peripherals receive 12V, 5V and/or 3.3V. However , I do receive 5v on the standby rail. So the 168vDC being supplied to the +5vstandby rail is going through this smaller transformer and providing the correct voltage. I guess I am getting something to the secondary side.The 400V cap is only showing 168V(dc) (waiting on cap tester now). Thinking this cap should be somewhere around 350-375V. This is the first discrepancy I find in-circuit. My second concern is the main transformer is not getting any power at all (red rectangle on photo).Question: If cap is good what in the circuit would prevent it from charging to an estimated 350-375V?I have added a few pictures indicating general observations from probing.Image Notes (below):Yellow arrows show general flow from introduction of 120AC.Red lines on photos showing the top is where the board splits and goes to the secondary side.Purple marks on photo showing the bottom-side of the PSU also show flow of voltage from introduction of 120AC.Would greatly appreciate any diagnostic suggestions.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 20, 2017, 05:12:41 am
content: Thanks for the reply. This unit was manufactured in Nov. 2013. It doesn't have the 220/120 switch mentioned. Although it does accept 100*240v 47-63Hz input. It is a 850w. Thanks for the article, I'll check it out.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 20, 2017, 06:13:13 am
content: The main "transformer" is a "Viking E216944-W H-P CWT 1209", for which I am unable to find any datasheet. Transformer has 6 terminals on the primary side and 8 terminals on the secondary side (DC side). (see bottom of board photo red rectangles for the terminals)You mentioned an "IC" chip that brought this to mind:I did look into WT7502 ("PC Power Supply Supervisor"). My understanding is that it looks for the correct voltages on input terminals before it will initiate power to actually turn the PSU on. NOTE I MIGHT BE MISUNDERSTANDING THIS COMPONENT. The green wire (on/off) that switches the power supply on and off connects to terminal 4 of the Supervisor. I also checked and did not find voltage on either V33, V5 or VSS (all input signals) to this Supervisor. I assumed the lack of input voltages is preventing the "Supervisor" from pushing power to the transformer/converter (Viking E216944 previously mentioned) so, I turned my search elsewhere for now. Kinda hard to suspect this supervisor as it is situated near the 12vDC output (to peripherals). If you can see the top view photo it is located just between where the blue (-12v) and black wires go into the board at the bottom-left of the photo. I assumed I was way off and moved closer to the primary side of the main looking for voltage to transform for the secondary side.It has two rectifiers that convert to DC just after the second choke>I greatly appreciate your food for thought on this; thank you for taking the time to respond.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 21, 2017, 12:34:27 am
content: Is there anyway I can get you some full-size photos (about 16MB)? I did have a little time to do some more work today, but need plenty more time to catch up on researching the things mentioned.Will try to answer all the questions this evening.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 21, 2017, 01:16:56 am
content: So these viking parts are transformers that lower voltage from 380vDC to working voltages of 12, 5 and 3.3 on the secondary side? Want to make sure I know what the components actually do.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 21, 2017, 01:42:48 am
content: ?Optocouplers or Power regulators?:I have identified three which straddle the primary and secondary sides of the board. Part number "L1213 817 B W" although I am trying to figure out what these are at this poiStill working....

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 21, 2017, 02:39:16 am
content: For the optos:Can I probe the anode and diode terminals (pins 1 and 2) to determine if this side, at least, of the optos are good or bad?I have made sure a fan was present (load) on the peripherals lines to ensure I would be alarmed at any changes while working. Wanted to make sure since the PSU's fan was removed with the case.Do believe I found a bad diode:Neg to cathode and pos to anode:528Reversed: 936Faulty? Would need to remove it to get data.Still working....

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 21, 2017, 06:33:39 am
content: I am going back and correcting my posts as I learn.So far:1. 123AC going into the board through choke>>filtering cap>>choke>>filtering cap; then2. 120AC into 2 rectifier bridges and 168 DC coming out of them.Question: Does the 168DC out of the 2 rectifiers appear correct? I can't get data from the rectifiers due to heat sink. Not ready to pull for testing yet. If you guys think the rectifiers are working properly then won't test them. Still studying on the "boost" you both mentioned.Essentially, I am getting 168VDC out of the two rectifiers. I don't understand the purpose of the cap "MEX JBN 105k450". (top right)If you click the photo and then to the right at photobucket you can DL the image and zoom in to read the text.

author: Messtechniker
author_rank: Frequent Contributor
timestamp: March 21, 2017, 10:46:46 am
content: Quote from: OpenCircuit on March 21, 2017, 02:39:16 amOne fan load may be not enough to satisfy the minimum load requirements of this rather large PSU. Or am I?

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 21, 2017, 05:50:32 pm
content: Mess....verified through manufacturer the single fan should suffice.PFC refers to pre-rectifier bridge(full)/DC conversion?

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 21, 2017, 11:10:41 pm
content: Pulled the MOSFETS (below) and did a bench test here:https://www.eevblog.com/forum/beginners/proper-mosfet-bench-test/msg1166902/#msg1166902Both are clearly working. Source terminals are connected to the large 400v Cap negative terminal.Could rectifiers have anything to do with the cap not reaching the correct voltage? If, 123AC is going into the rectifiers (no id marks since they are pancaked into a heat sink) would the EXPECTED output value be 168DC?

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 12:14:32 am
content: After the ac input, two chokes, and two filtering caps, the AC hot and neutral come together through two SG1s. Can anyone explain what the EE's purpose was here?Chip "GR8875R C2U01" (SOP 7), seems to be at the heart of this:www.grenergy-ic.com/attach/product/20120607130542_pic.pdfFull size image:https://postimg.org/image/smtd5jtz1/

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 01:47:04 am
content: Quote from: evb149 on March 22, 2017, 01:05:52 am1. Will certainly try to fit this into the troubleshooting. I suppose it would be much easier for the more informed (pretty much everyone here) to make suggestions that are always appreciated.2. PFC IC power fact correction integrated circuit....uhmmm....where is that? I did find a GR8875 that I plan to look into.3. RMS vs non-RMS or peak or....? Sorry, not an engineer by any means. Simply setting my DMM or DVM (FLuke 114 to Auto-V LoZ and it gives me anumber.4. Sorry it is just above my head. I greatly appreciate the information though and the time taken to reply. Will see what I can learn about it.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 01:58:22 am
content: Quote from: evb149 on March 20, 2017, 07:38:55 amThe board off to the side has two large yellow and two large black wires going into it to supply DC. Then off to the side of that same board has most all of the 3.3 , all of the 5v and about half of the 12v signals going to the peripherals. -12v, PCG, and green (on/off )wire do not touch this board off to the side.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 02:28:20 am
content: Quote from: evb149 on March 21, 2017, 03:47:04 amYou were correct. Pulled fro circuit and tested fine.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 03:37:12 am
content: Quote from: blueskull on March 22, 2017, 01:14:48 amMy fundamental understanding: Power supply on and "current" is being consumed by PC peripherals which the IC senses and a resulting voltage drop at the controller "chip" so the PFC circuit allows more power to be converted "filling" the PET cap (400v, 470uF) to maintain current DC power needs?

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 03:58:38 am
content: Quote from: evb149 on March 22, 2017, 01:16:47 am1. Sorry the only values I can tell you with confidence is 123vAC input and the PET cap is 168vDC In US. No oscilloscope.2. So, the AC wave is being rectified into DC but it is not getting boosted? Just making sure I understand.3. This makes sense to ensure you maintain the desired vDC when power is "drawn" through transformer. Hope this indicates a vague understanding. The main transformer has 6 terminals on the primary side and 8 on secondary side.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 04:18:00 am
content: Trying to keep up with you.PFC IC?:Note: the heatsink and FETS that I tested earlier are still removed.Another angle:

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 04:26:06 am
content: Quote from: evb149 on March 22, 2017, 02:53:33 amUnfortunately no.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 04:52:44 am
content: Quote from: evb149 on March 22, 2017, 04:01:19 amAfter the AC/DC rectifiers:https://postimg.org/image/8mvz8jtn1/Make sure to click on the picture so you can zoom in.I marked that main cap as 400v so you would have perspective of the board. Measuring the voltage is 168 across the + and - terminals of the cap.You can download that image to your PC then open with paint and draw on it...then post if you have time.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 05:21:56 am
content: Quote from: evb149 on March 22, 2017, 04:26:45 am1. the other side of the vertically opposing board has "CWO3X f53028J5 150" (8 Pin) and I will need to verify that lighting is terrible at the moment.2. The main suspected PFC IC is 16 pinon the vertically opposing board.3. Awesome... PFC AFTER ( I wasn't sure) the rectifiers.Is this a boost coil?:

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 05:35:25 am
content: Quote from: blueskull on March 22, 2017, 04:25:19 amI did a simple diode test across pins 1 and 2 and did get an inconsistent reading on U5(see photos), but tracing the board this seems it could pose a problem only after the boost in the PFC. Definitely going to look at them as soon as I get the PFC boosting.I will conduct a test (bench if needed) of the optos after I get it put back together. This may never happen if my probes slip [bang and smoke],at :54 seconds is applicableTomorrow I might pull that heat sink blocking the suspected PFC controller to get the datasheet. Is that something I might be able to buy somewhere?

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 06:03:49 am
content: Quote from: blueskull on March 22, 2017, 05:56:44 amI have this off at the moment:Going to get that PFC IC code tomorrow after I pull the other heat sink blocking access, much easier than pulling the vertical board with the PFC IC on it. Can ALMOST read it with dental mirror.Quote from: blueskull on March 22, 2017, 05:56:44 am

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 06:14:58 am
content: I just need to trace the leads from this "doughnut" and see where they lead me. ugh...sleep

author: janoc
author_rank: Super Contributor
timestamp: March 22, 2017, 09:28:43 am
content: Quote from: evb149 on March 22, 2017, 04:07:26 amOh cool, I have always been curious how the PFC was working in these supplies. Thanks for posting these! One learns something new every day.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 06:11:21 pm
content: PFC IC Controller(CM6800TX): "The CM6800 is a controller for power factor corrected switched mode power supplers."Working on rudimentary schematics now.Datasheet:https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwiimMbz2urSAhVK2GMKHUS5D2oQFggfMAA&url=http%3A%2F%2Fwww.champion-micro.com%2Fdatasheet%2FAnalog%2520Device%2FCM6800.pdf&usg=AFQjCNG0hlXFKyG8nqJ015hesi3hfDp6KA&sig2=nxxLSTTSYGhoIpgRVY0iBA&cad=rjaClick for full size:

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 07:46:10 pm
content: Did a bit of tracing today trying to focus on the PFC and IC hoping to figure out the circuitry. Maybe, I should just call Corsair and ask. Some of the symbols were too complex, so I just made a note or a small pic when I didn't know what the "thing" is/was.I was able to score one more identical broken power supply and one more very similar broken PSU from the same manufacturer! Should be a very inexpensive lesson in microelectronics.Will catch up on responses later today I hope. Click image below then click it again when it takes you to the new page to really zoom in close.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 22, 2017, 08:09:30 pm
content: Does the 25v Cap look burned?:Other Side of PFC Board:Will start tracing at the optocouplers next time.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 23, 2017, 12:08:15 am
content: The color is like ink that runs across onto the PFC controller next to it on the left-just noticed in the photo. Was sure hoping I could find a problem somewhere obvious, replacing that PFC controller does not look like fun. Getting my hand pump on there does not want to extract the solder with the tight pin configuration. Oh well that is in the future.Ordered cap tester a few days ago....going to be a long wait.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 23, 2017, 02:35:36 am
content: Quote from: evb149 on March 23, 2017, 01:15:15 amThis is music to my ears.While tracing the opto circuits on the primary side I was thinking about pulling them for a simple bench test in a bread board.....only 4 terminals and I have a few major components already off. Although not sure how sensitive they are to heat.Really good article on the power supplies explaining PFC. Got a good laugh at a complexity comment on page 3, "Reduced complexity for active PFC...." Circuitry on this board is wow.I noticed that when you click my thumbnail images posted at postimg.org you can actually download the original in full resolution and zoom in. Excellent website for the larger photos.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 23, 2017, 02:40:35 am
content: Here is some of the optocoupler circuitry:

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 23, 2017, 02:54:47 am
content: I originally thought this "chip" had some burn, but not so sure now. Wanted to post to get other opinion(s).

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 23, 2017, 03:13:05 am
content: Below is what I pulled so I could read the vertical board with the PFC controller. Have not traced their curcuits yet, but thinking I might after the optocouplers on the secondary side. It is situated just before the main transformer.CET:https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwj78t_51OvSAhUK64MKHakDAGoQFggcMAA&url=http%3A%2F%2Fweb2.cet-mos.com%2FPDF%2FCET-MOS%2FTO-220-263-N%2FCET_CEP04N7G(F).PDF&usg=AFQjCNHW_7K6QYxFmb5sRLdgDZqz6N15-Q&sig2=GisGAHP7kF-QntmmhUEDQw&cad=rjaK18A50Ss:https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=0ahUKEwjwg9Se1evSAhUZ3YMKHV18AyoQFgg0MAc&url=http%3A%2F%2Fwww.farnell.com%2Fdatasheets%2F2007926.pdf&usg=AFQjCNFLBqJfIpw2T0uZYkEqygiBzE_K3g&sig2=pP7an8DyFphGSEAU2ulzEQ&cad=rjaEEEwwww a boost diode below.https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwisiZet1OvSAhUj7IMKHSobAVUQFggdMAA&url=http%3A%2F%2Fwww.st.com%2Fresource%2Fen%2Fdatasheet%2Fstth506d.pdf&usg=AFQjCNFS8vimgpgu6ap69WgtKCawYb2jQQ&sig2=UA-LKOvnOhomaBFX3afpQg&bvm=bv.150475504,d.amc&cad=rja

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 23, 2017, 03:25:40 am
content: Boost diode ^^^ tests good "854" with negative probe to terminal 1 and "1" with negative probe to terminal 2-red always on other terminal.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 23, 2017, 04:08:48 am
content: Quote from: evb149 on March 22, 2017, 06:22:08 amInteresting fix for sure; very informative, especially for that PS229 chip. He did have power on all of the rails, where I had nothing. I can sure see something like that as one possibility with mine.I wonder if that PS229 will fail prematurely since he had to increase the voltage through the pin to get a "signal" across to the other side....?

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 24, 2017, 12:45:24 am
content: Fuse is/was a ceramic 250v 12A; "LF.T12AH250VP"Is it slow-burn or fast?

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 24, 2017, 01:19:37 am
content: Running out of steam. Eliminating all the small resistors now and trying to get just the main things like transistors, optos, transformers, caps, and output circuits to that sub-board. It appears the main board is supplying +12v+ to that board off to the side which then supplies +5v and +3.3v to peripherals.*Some peripherals still receive +12v directly from the main board.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 24, 2017, 01:21:56 am
content: The second PSU with the same model number arrived, but it is from 2011 and the board is way different.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 24, 2017, 04:41:30 am
content: Here is the board off to the side:

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 24, 2017, 05:29:18 am
content: So the "T" in "F.T12AH250VP" stands for time-delay/slow-blow.Good link on the matter:http://www.instructables.com/id/How-To-Identify-And-Replace-A-Blown-Fuse-1/