PSU Blown components identification

Discussion in 'Technical Repair' started by Michael Netterberg, Apr 25, 2017.

  1. Michael Netterberg

    Thread Starter New Member

    Apr 24, 2017
    3
    0
    Hi Guys,

    I am trying to repair the PSU on two Philips Airfryers HD9240 - I have looked for the schematics online but cant find anything. One of these units is my own and one with the exact same fault on a friends. Naturally both just out of warranty.

    I have narrowed it down to two blown resistors and a 50v 10uf capacitor. One of the boards a Viper 16L IC has cracked as well, I suspect from the heat when the capacitor went, so will be replacing them on both boards as well.

    The capacitor and the IC are easy enough to identify, the issue I am having is trying to identify the correct replacement resistors. On both boards they are blackened and cracked open. I cannot make out all the colours, they both start with brown and end with gold. the rest I am not sure of, if it is discolorationdue to heat or not, also not sure if they are 4 or 5 band resistors - depending on the light you look under, it could be either. I tried measuring them on a DMM but they are dead.

    unfortunately I do not know enough about circuit design to be able to work out what is needed.

    If anybody has repaired one of these before or knows where I can get hold of the schematics it would be greatly appreciated - or if there is a way to work out the value of the resistors... (I have seen some articles on scratching off the insulation and trying to measure it that way so might go down that route)

    Please see pics of board and resistors.

    thanks in advance!
    -Mike
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    6,708
    1,082
    Looks like Brown, Grey, Black, Gold

    18 ohms 5% 5W this is a preferred value.

    If it's White instead of Grey, it's 19 ohms,, they both go in series with the AC supply to the bridge rectifier for the chip supply.

    The chip is a 7 pin switchmode chopper

    Datasheet

    http://www.st.com/en/power-management/viper16.html
     
    Last edited: Apr 25, 2017
  3. Michael Netterberg

    Thread Starter New Member

    Apr 24, 2017
    3
    0
    Thank you for your reply much appreciated!!

    I will get on with ordering bits get these repaired!
     
  4. Vladimir P

    New Member

    Sep 18, 2017
    1
    0
    Hi Michael,
    I have 100% exact problem with same model. I will appreciate if you share how did you end up with this problem.
    Thanks!
     
  5. bwilliams60

    Well-Known Member

    Nov 18, 2012
    878
    140
    If you can, try measuring each half of the resistor from the open to the leg and then add them together. It should put you close but Dodgy is probably right.
     
  6. Rinus

    New Member

    Sep 27, 2017
    1
    0
    No Update yet? Have the exact same problem.. I suspect the transformer also has a short replaced the resistors and capacitator and one of the resistors burned out again. (instantly has to be a short)
     
  7. Jhojo

    New Member

    Sep 29, 2017
    4
    0
    Same here, it had 2x 33Ohms 5% resistors and the 50v 10uf capacitor was capped, after replacing them it instantly failed with burned out resistor. Should I order a Viper16LN IC and two resistors 47Ohms to fix it?

    My IC is impossible to read.

    On a side note, the Airfryer XL has a big design flaw. the heat and moisture goes up behind the casing, and ends up on the PSU and key panel.

    I also read in the service manual that build before 2015 need the PSU and key panel replaced together. Anyone know why that is?
     
  8. Jhojo

    New Member

    Sep 29, 2017
    4
    0
    Correction 33Ohms should be 31Ohms. The colours of the rings were: Orange, Brown, Black, Gold
     
  9. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    6,708
    1,082
    If it's blown up the resistors and capacitor, then the chip will most certainly have caused it, and possibly taken out the bridge rectifier too.
     
  10. Jhojo

    New Member

    Sep 29, 2017
    4
    0
    I replaced the chip, capacitor and resistors. It doesn't short out anymore, display will light up for halve a sec. and will do that blinking wise. Would this be the cause of the bridge rectifier?

    If any one needs the above chips, capacitor and resistors, give me a message, I have spares.
     
  11. Edwin Holt

    New Member

    Oct 11, 2017
    1
    0
    Can you ship the parts to the netherlands ? I tried to send you a PM, but i don't know how to do this.
     
  12. Jhojo

    New Member

    Sep 29, 2017
    4
    0
    I can't find the link to a conversation starter either. But send me a mail : jhojotnt at gmail and I can help you out.
     
  13. Michael Netterberg

    Thread Starter New Member

    Apr 24, 2017
    3
    0
    Hi guys apologies for the delay in responding. I had my notifications turned off and didnt see the responses.

    On one I replaced the viper16 chip the two resistors and the small 10uf capacitor that was blown which fixed the one airfryer and it has been running since May with no problems - the other airfryer ( my friends) seemed to have had another problem as well - his had failed around 1 year before mine and the fix i did on both only worked briefly for his - I have now had to replace all the capacitors on his board along with the Viper16 chip and the 2x resistors - this seems to have resolved the issue his airfryer is working as per normal again.

    hope this helps!
    -Mike
     
  14. macrop

    New Member

    Dec 9, 2017
    1
    0
    Hi everyone - new member here. I too have the same issue with my Philips Airfryer (XL 9240) - no power up. Dismantled it and the blackened resistors stood out on the PCB pretty quickly. Once I de-soldered the resistors (both open circuit), I noticed a hair line crack on one of the resistors - (must have been a hard final fault to pop both in series. So in total - both resistors have failed, the 10uF cap is bulging, there's a burnt pin on the SMPS IC, and the bridge rectifier diode values aren't quite right so I'll replace that to. I've ordered some replacement components from RS so I'll update this thread when they arrive and if I'm successful in the repair. I had to to buy a minimum of 5 of each component but the cost was still around AUD$15 which isn't too bad.

    My machine is around 2-3 years old and stopped working a couple of weeks ago. I use it probably once every two weeks.
     
  15. Reaperman

    New Member

    Dec 27, 2017
    2
    0
    Hey guys,
    thank you for this thread and all informations about this PSU Board. My board have the same issue like ours....The resistors are 31Ohms? Is this info correct?
     
  16. Meadow

    New Member

    Jan 8, 2018
    2
    0
    Thank you guys for the work done !:)
    It seems to be a design issue...
    Mine too stopped working last week. When I opened it, same symptoms: 2 resistors, the same cap is bulged and the "burned" IC.
    Can someone confirm the value of the resistor and more important minimum rated power ?
    I could read previously 5W but the ones found on the board seem a bit small for being 5W.

    Thank you in advance !
     
  17. Reaperman

    New Member

    Dec 27, 2017
    2
    0
    Hello Meadow,

    I I replaced the resistors with new 31Ohm/5W. But I think 5W its too big...3W can be the original.
    I replaced the Viper, the Cap and the bridge rectifier too. The Airfryer works so far without problems...

    Greetings
    Reaperman
     
  18. Meadow

    New Member

    Jan 8, 2018
    2
    0
    Thank you Reaperman !
    Just what I need to know to move on :)

    Greetings !
     
  19. twang

    New Member

    Saturday
    1
    0
    Hello, thanks to you all for the information above it is invaluable. I have an airfryer with the same problem, same PSU. Both resistors are blown, cap looks OK, rectifier looks OK. the chip is difficult, it looks odd, maybe a burn on the top but no sign of any issues around the pins. The unusual thing is on the board underside smc diode D1 is destroyed completely. Can anyone help me with a part number for this item. It is only quite small compared to the other diodes.
     
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