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
    2
    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
    6,476
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    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
    2
    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

    Active Member

    Nov 18, 2012
    850
    136
    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
    6,476
    1,024
    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.
     
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