Question about System Power Supplies

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Faulty Enermax Liberty ELT620AWT

My PSU will not power up. When AC is applied the fan starts to turn for about 0.5 sec then stops and I have no o/p on any rail. The +5VSB is present. I think theat U7 (PS223 monitoring IC) is faulty preventing the PSU froms starting but cannot verify this nor locate a suitable replacement

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  • 14 more comments 
  • Dave May 22, 2008

    I have tried to power up PSU connected to my MoBo etc, with no load, and with a light loade (2 old HDD). It used to power up and run perfectly if I manually pulled pin 16 of the AXT 24 pin connector (PS_ON) to ground but it no longer does this. That's why I suspect the PS223 IC as this is where pin 16 goes to. I have verified that the AC is getting to pcb, the firts stage rectifier also appears to work as I get the HV DC. Without a cct diagram though I am poking in the dark somewhat.

  • Dave May 22, 2008

    Thanks. I already have the PS223 datasheet.

    The PS223 pin votlages are as follows

    PIN - SIG - Voltage

    1 PGI - 0

    2 GND - 0

    3 FPO/ - 1.15VDC

    4 PSON/ - 0

    5 IS12A - 0

    6 RI - 0.72VDC

    7 IS12B - 0

    8 VS12B - 0

    9 OTP - 0.2VDC

    10 IS5 - 0

    11 IS33 - 0

    12 VS12A - 0

    13 VS33 - 0

    14 VS5 - 0

    15 VCC - 5.19VDC

    16 PGO - 0

    A simple ohm measurement across the various o/p donot reveal any hard shorts. These are the measurements I am getting WRT GND.

    +3.3VDC (orange) - 16 ohms
    +5VDC (red) - 30 ohms
    +12VDC (yellow) - 75 ohms
    -12VDC (Blue) - 1.5K
    PWR_OK (Grey) 10K
    PWR_ON (Green) 20K
    +5VSB (Purple) 450 ohms

  • Dave May 22, 2008

    Pin 4 of PS223 is connected to pin 16 of the 24 pin connector via a 1K resistor so pulling pin 16 low will not have any effect as pin 4 of the PS223 is already at 0VDC. None of the other voltages change either

  • Dave May 22, 2008

    With AC ON and PSU in OFF state the pin 4 of PS223 is 0Vdc isolated from all other circuitry. Pin 4 measures 20K WRT to Vcc pin 15 and a20k WRT GND pin 2

    If I trigger pin 4 with 5VDC the PSU momentarily energises then stops - same effect as if I power on from cold.

    I am confused as to how this chip stops the PSU from starting... There are 2 outputs which I assumed were used to enable the PSU however tracing pin 3 FPO/, It goes via a 750R resister to VCC - The ref cct on data sheet shows it with a LED and resistor to vcc. I conclude that this is a "visual" fault indicator in the ref cct. The other is pin 16 PGO witch goes direct to pin 8 of the ATX connector. Neither seem to in any way control the PSU? I am confused but since pin 4 is not correct voltage (+5V) when floating, and pin 3 is low (1.15V) which I think is FAULT conditiion and pin 16 is low (0v) which I think is "power OK" condition. I conclude that the PS223 is in fact faulty. Can you at least clarify how the PS223 enables the PSU

  • Dave May 22, 2008

    I must admit I have been thinking that too... I was going to disconnect pin 3 and/or 16 to see if it allowed the PSU to run.

  • Dave May 22, 2008

    ok I decided on disconnecting pin 3 of the PS223. I desoldered the 750R and let pin 3 float. Applying AC the PSU immediately came to life ans powered the 2 xHDD and 2X CDROM I was using as load. Checking all rails they all appear OK.

    Checking the PS223 pins in this state...

    The PS223 pin votlages are as follows

    PIN - SIG - Voltage

    1 PGI - 1.88vdc
    2 GND - 0
    3 FPO/ - 0.48VDC
    4 PSON/ - 0
    5 IS12A - 12vdc
    6 RI - 0.72VDC
    7 IS12B - 11.82vdc
    8 VS12B - 12.16vdc
    9 OTP - 0.27VDC
    10 IS5 - 4.85vdc
    11 IS33 - 0.73
    12 VS12A - 12.15vdc
    13 VS33 - 2.51vdc
    14 VS5 - 5.12vdc
    15 VCC - 5.19VDC
    16 PGO - 5.0vdc

    The other side of the 750R is still +5vdc.

    This means pin 4 is shorted to ground intrenally as it should be pulled HI by the 20K internal resistor. I am not sure if the FPO/ o/p is being driven low of if it is in a failed state internally???

    Also the voltages on pin 11 IS33 (0.73vdc) and on pin VS33 (2.51vdc) seem low compared to the other rail inputs.

  • Dave May 22, 2008

    Yes the PSU now fires up immediately I apply AC. No not ideal for use... Yet. I intend on fixing it completely. I may have located a supplier of the PS223 chip so hopefully I will have a spare within a week from OS. My concern now focuses on the signal levels on pins 11 and 13. Are they wrong or OK? Are they the reason the PSU is disabled? Are they low because the PS223 is loading those lines? I'll disconnect them tomorrow and post back as it's almost midnite here is OZ

  • Dave May 23, 2008

    Having disconnected pins 11 and 13 individually and together, it seems to me that the +ve comparator input pin 11 is connected internally to pin 13 (not a hard short though) causing the internal logic to detect a "fault" driving pin 3 (PFO/) low disabling the PSU. This in addition to pin 4 PS_ON/ being internally pulled to 0V instead of +5V maakes for a very unhealthy PS223 I.C.

    Heres hoping I can get a new one soon.

  • Dave May 24, 2008

    Wonering if you can point me in the direction of a similar IC that could be implemented to replace the PS223 which seems impossible to find. I am capable of moding the board, building a pigyback pcb or what ever is required. I dont want to build a functional replacemet from scratch if I can avoid it.

  • Dave May 24, 2008

    Thanks. I'll look at the options you have suggested

  • Dave Jun 30, 2008

    I have managed to locate a PS223 IC so hopefully I will have it soon to install and test

  • Dave Jun 30, 2008

    I dont remember rating anything?? How do I review the rating?

  • Dave Jun 30, 2008

    there is no option to change the rating

  • Dave Jul 09, 2008

    The PS223 I was hoping to get fell thru but I have discovered that the Fairchild SG6520 is a pin for pin and functional replacement. On order from Mouser Electronics in the USA so will have Ic in a couple weeks.

  • Dave Jul 24, 2008

    I have installed the new IC and on the bench, the PSU turns on but when installed in the 'old' PC with the GA-K8NF9 it will not unless I manually short pin 16 to ground...



    The weird thing is that the PSU works just fine in my new rig with the GA-EP35DS3R powers on/off as expeced.



    Even weirder is that the other PSU works just fine in both the 'old' and 'new' PC's...

  • Dave Sep 08, 2008

    the Fairchild SG6520 works just fine

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  • Master
  • 6,966 Answers

Hi,

Are you checking the voltage outputs of the PSU with it connected to a motherboard or standalone? Most designs will not power up if there is excessive load (as in a short/high current), however, there are also designs that will not power up if there is no load.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.

Posted on May 22, 2008

  • 11 more comments 
  • Louie  Role
    Louie Role May 22, 2008

    Perhaps there is a way you can verify if the PS223 is working, pls reference this spec sheet. There is a typical application schematic diagram which may be of information. Additionally, typical pin voltage readings may be gleamed from the said document.

  • Louie  Role
    Louie Role May 22, 2008

    I understand the need for the schematic, but of course Enermax wouldn't be publishing this for reasons we both know hence my suggestion of winging it from the schematic of the data sheet.

    pls check if pin 4 of PS223 would change from 0 to ~5 when you pull the PSU's connector pin 16 to ground (POWON); pls also check if there is a similar change in pins 3 & 10 (again of the PS223) from 1.15 & 0 respectively to 0/~5 & ~5.

    would appreciate update on results of voltage readings.


  • Louie  Role
    Louie Role May 22, 2008

    pin 4 of PS223 and therefore pin 16 of the connector should have an initial ~5VDC if AC mains is supplied. The 5VDC exists since as you posted pin 15 Vcc of the IC reads 5.19. Internally, there is a 20K resistor from the Vcc supply towards pin 4 (PSON) of the PS223 and therefore should read high at PSU OFF. Triggering the PSU to Power On/Start as you posted is grounding pin 16 of the connector which in effect brings down pin 4 of the PS223 which if you would reference the Data Sheet's Timing Chart, you would notice that PSON low is equal to PSON/turn on.

    Suggestion to see if the problem is internal to the PS223 or external to it. Float pin 4 by desoldering it or removing all components attached to it such as the 1K resistor. With AC in/PSU off, pin 4 should read high. Thereafter, grounding it should trigger your fan/PSUON.

    If it still reads low @ AC in/PSU off (floated and no components) then you have a no triggering PS223; defective.

    Which brings to the next possible concern, where to purchase a new PS223. They are not readily available as the LM series of regulator/monitors. And I am not aware of a substitute.


  • Louie  Role
    Louie Role May 22, 2008

    I am tempted to think that the PS223 is not meant to kick start the PSU but rather to prevent it from running based on any number of faults. As the name/description implies, it is there to monitor and shutdown the PSU in the event of over current or over temperature.

    Which leads me to suggest, try running the PSU without the PS223.


  • Louie  Role
    Louie Role May 22, 2008

    Re your query :...Can you at least clarify how the PS223 enables the PSU..." I don't think it enables but rather, it disables the PSU. All SMPS has an inverter/chopper and some sort of controller. The output of the PS223 could be wired to trigger the controller to OFF if in its monitoring it detects a fault.

  • Louie  Role
    Louie Role May 22, 2008

    ahhh, of course, pins 3 & 16 are the only outputs....

  • Louie  Role
    Louie Role May 22, 2008

    Did I understand you right, the PSU powered itself ON when AC was applied? If yes, then the PS223 is acting as the inverter/chopper controller and not only as a trigger/source. In effect the PSU operates like the old ATs utilizing mechanical switching of the AC for power on/off.

    I think any erroneous voltage/logic state at any of the inputs of the PS223 will not have any effect. Though am afraid with todays MB, WOL, hibernate/sleep and others, the PSU will no longer be appropriate.


  • Louie  Role
    Louie Role May 24, 2008

    The closest I could think of is a Motorola or Texas Instrument TL494 control IC. Data sheets are here and here respectively. An application diagram (for a lower wattage) maybe found here. It is very possible that you may have to use 2 of the TL494 to simulate the 4 channel capability of the PL223. Additionally the outputs of the 2 TL494 will have to pass through a dual OR gate.

  • Louie  Role
    Louie Role Jun 30, 2008

    and hello again,

    Appreciate the update and will look forward to any new development(s) if and when.

    A favor if I may ask, would you be so kind as to re-valuate the rating you gave me? Perhaps unknown to you, the "Thanks for Trying" actually brought my ratings down which is already a challenge as it is to attain and maintain. Hope you understand.

    Thanks much and good luck again.


  • Louie  Role
    Louie Role Jun 30, 2008

    Thanks for taking the time. Below my last response would be:
    "Was this solution helpful? Show your Appreciation by rating it:"
    Thereafter a selection of:
    Inappropriate Thanks for Trying Helpful FixYa!

    The first two (2) would give me a negative mark while the last two would improve my ratings.

  • Louie  Role
    Louie Role Jun 30, 2008

    Copy that, thanks anyway. No prob.

    Again will look forward hearing from you soon as the new PS223 IC is available and you have repaired the PSU. Lots of luck.

  • Louie  Role
    Louie Role Jul 09, 2008

    Thats great, the SG6520 would be relatively easier t get.

    Thanks for the update.

    Goodluck and would look forward how it goes.

    Cheers.


  • Louie  Role
    Louie Role Sep 08, 2008

    Appreciate sharing the findings. Am sure a lot of techs would benefit.

    Cheers.


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