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Condenser dryer main board power fault

Discussion in 'Troubleshooting and Repair' started by Notallbad, Dec 6, 2018.

  1. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    Please could someone help fix this board.
    Replaced so far:
    U1 LNK364PN (shorted drain-source)
    R4 39ohm 2W resistor (burnt out)
    C1 MKP339 100nf 310Vac X2 safety film cap (low capacitance, replaced with MKP X2 0.1uF 310Vac)
    D2 1N4007 (replaced with UF4007, was shorted)
    D1, D2, D9, D11, D12, D13, D14 1N4007 (replaced with UF4007's, but all seemed to test ok)

    All elec caps test ok out of circuit with cap meter, within 10-15% tolerance.

    VDR1 has high resistance out of circuit, over 2Mohms.

    The 5 relays test ok, 9v switches them on / off.

    The transformer BV 201 0146 reads 15kohms across primary and sec are 380ohms and 300ohms. (in-circuit)

    The dryer was on and in use when the fault occurred, when I returned to remove the laundry it was non-responsive.

    The dryer is dead when powered on i.e no led's light up on the front panel.
    Only the drum light illuminates when the door is opened - this is operated via the door switch powered directly from the Power switch.

    I have photos and an illustration but unable to upload at the moment.

    Many thanks.
     
  2. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    I really need to get the photos up, hoping to do so very soon!

    Is there a minimum number of posts I need?
     
  3. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    hope these help
     

    Attached Files:

  4. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    Could someone confirm the spec of the original resistor please.

    (I've replaced it with a 39 ohm 2w 5% tolerance resistor.)

    The main body measures 12mm long by 4.5mm wide, so guessing its a 2w resistor.

    The colour (to me) looks like
    1st band - orange
    2nd band - not sure because its burnt but sure its either white or grey
    3rd band - black
    4th band - gold

    So, if the other colours are correct the resistor was in the range of between 30 and 39 ohms depending on the 2nd band colour.
     

    Attached Files:

  5. Tha fios agaibh

    Tha fios agaibh

    1,888
    597
    Aug 11, 2014
    I think your right that it's a 39Ω.
     
  6. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    Thats already been replaced.

    C1 MKP339 100nf 310Vac X2 safety film cap (low capacitance, replaced with MKP X2 0.1uF 310Vac)
     
  7. Tha fios agaibh

    Tha fios agaibh

    1,888
    597
    Aug 11, 2014
    Yes, I noticed that. You've already replaced most of the obvious parts.
    I would install the board and try and follow the incoming voltage and see where you start to loose it.
    Hopefully the smd parts on the back haven't taken a hit when it went poof.
     
  8. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    I have actually swapped out the 78M05.

    The surface mount resistors all seem to be within range though that is in-circuit.

    The surface mount diodes all seem ok apart from a few that read both ways, thats because they are in parallel with relay coils.

    Just hoping the micro controller hasnt been fried.
     
    Last edited: Dec 7, 2018
  9. Tha fios agaibh

    Tha fios agaibh

    1,888
    597
    Aug 11, 2014
    I would expect a relay click , lights, or some sign of life even if the microcontroller was out.
    Maybe something external to the board such as door switch or programer dial is holding you out?
    I'd look at the DC power rail ckt, and trace back the power button to see how it triggers the power to come on.
     
  10. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    All ancillary devices checked and appear good i.e mains filter, power switch, door lock, heating circuit, motor/run cap, drain pump, wiring, thermostats, float switch, programme dial.

    Only getting 0.6v output on the 78M05 that feeds the microcontroller VCC pins 5, 17 & AVCC 27 (gnd tab to output pin).

    And 3.6v on input pin (gnd tab to input pin).

    0.6v drop across input and output pins.

    The 3.6v is from LNK364PN which has 5.8v on the BP pin.

    Shall check the opto-coupler next.

    I did wonder if the microcontroller is in 'sleep mode' as it would appear it has several at different levels. So maybe it needs a reset, short the 'reset' pin to gnd with a suitable resistor.

    Also, FB1 on microcontroller pin 17 Vcc reads 0 ohms.
     
  11. Tha fios agaibh

    Tha fios agaibh

    1,888
    597
    Aug 11, 2014
    Sure sounds like something to do with the LNK364PN circuit. Yes, the opto-coupler is a likely suspect. I'd also check the bypass cap if you haven't already.
     
  12. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    The 78M05 needs at least 5v to operate and I would think it should be at least around 9v as it also drives the 12v relay coils. So definately something relating back to the LNK364PN it would seem.

    The section of the board i.e xfrm sec windings down to the optocoupler will only be working when relay RL3 triggers which latches the mains "N' via the drum door closing (this would also start the drum rotating) which is a safety feature to stop the running programme when the door is open during a cycle, so would expect the led function lights to be on still.

    All the other relays only operate the drum motor, drain pump and heating circuits so not critical to powering up. So like you say 'would expect led's to be on'.

    Under normal working conditions the leds were on at power up, at the end of a programme cycle and when the drum door was opened mid-cycle.
     
    Last edited: Dec 8, 2018
  13. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    If the BP pin on LNK364PN internally generates the 5.8v where would 9-12v to drive the relays be generated?

    Theres a steady 320vdc across the 10uF 400v caps C3 & C4.
     
    Last edited: Dec 8, 2018
  14. 73's de Edd

    73's de Edd

    2,645
    1,074
    Aug 21, 2015
    Sir notallbad . . . . .

    Let me provide a close together view of the two board sides with a color coded mark up of the principal components of interest.
    I additionally provided a nearby, viewable schematic of a typical application note from that LNK364's IC's manufacturer

    I dood it . . . . .in my interpreting it as best as I could, with it using a NON CONTRASTING foil pattern of two shades of green . . . further
    impacted upon, with both sub par edge lighting and glaring central light reflections.

    BASIC DESIGN CONCEPT . . . . .

    Looking at the top left corner of the center photo, we see the switch mode power transformer that is going to be handling both variable
    width and bursts of square waves in the 10's to 100's of K's frequency . . . . it is being power demand specific.

    Possibly 2 diodes of a discrete build up of 4 for a a FWB rectifier, reside at the left of the power transformer. Then I seem to see the PINK RECTANGLE electrolytics with mid RED RECTANGLE 1 MH inductor making a pi filtering network for creating raw DC.
    In AMERIKANSKI use, I expect a developed ~160 raw DC being delivered, if being You-Are-A-Peeing voltage , I am expecting twice that level . . . . and if you touch it . . . . .You . . . .Will-Be-A-Peeing . . . . . a la Delmer Dumbnuttz.
    GIVE us the capacitances and voltage ratings of the two E-caps just covered . . . I now see 10's @ 400VDC listed above . . ., and ALSO, those of the nearby C23 and C22 , which must be related to filtering the output of the secondary of the power transformer, as being derived from some unviewable Schottky rectifiers.

    That is being one of the units raw DC power supplies, you also have a minor ancillary one made up of the . . .refer to schema . ..CY type of poly cap that uses its capacitance reactance to voltage and power drop down the rawline AC from its left lead connection, and then out, to flow thru to the D5 diode to then create a minor DC supply. It associates with the VR1 zener and the LED within the U2 optical isolator to regulate against overvoltage when the LNK initially powers up . Then the LNK overrides and provides the required / demanded power level.

    I estimate that there will be two power supply levels created and am so using a RED draw in of the 16 VDC supply output.
    It might be 12 or 15VDC , you will just have to confirm . . . as I currently think that your LNK circuitry is not working. ***

    Also on the foil side of the board I see what probably will be a U4 5 volt three terminal regulator associated with being the u/p supply source and probably the before and after E-caps that I have YELLOW RECTANGLED at the center bottom of the PCB.
    (Give those Cap/Voltage ratings . . . along with the two that are near the LNK cluster.
    Of course, the other YELLOW markups are being the LNK and the 817 optical isolator for regulation feedback.

    And there is the YELLOW markups of your burnt open resistor . . .I have seen many different values being used.

    TRY THIS ONE . . . .

    Take your pulled original . . .HIGHLY likely .. . of being a metal film resistor and jump short its two ends together and connect to one of the leads of an ohmmeter set to low scale ohms. Take a naked #11 Exacto blade and grip it in constant contact with the other ohmmeter lead and initially stab to the paired resistor leads, to confirm near zero ohms continuity.
    AND THEN . . . .you gently scrape at MID point of the resistor to just easily creep thru the conformal paint coating and then I heavily suspect an ohmic reading will appear .
    Double that resistance value and it should be right at your original resistors value.
    No workee ? then move down to the " quarter " distance portions from the ends and compute accordingly, on a found resistance completion..

    The RED circled BLUE device "foil path reads" it as being a line spike MOV.

    If you now have full raw DC voltage thru the primary of the power transformer to the 364's internal PWR FET, but with no developed secondary supply DC voltage from the transformer secondary . . . . . inform us and come back for our testing of the 364 and . . . .The Rest of the Story. . . . .
    Gud . . . Day . . . .

    YOUR TECHNO REFERENCING . . . . .

    [​IMG]



    73's de Edd
    . . . . . . . . . . . .


    i fullie souport publik edekashun.
     
    Last edited: Dec 8, 2018
    Richard9025 and Tha fios agaibh like this.
  15. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    Thanks very much but please bear with me whilst I do my best to answer you.

    Very grateful!
     
  16. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    'Sir notallbad . . . . .

    Let me provide a close together view of the two board sides with a color coded mark up of the principal components of interest.
    I additionally provided a nearby, viewable schematic of a typical application note from that LNK364's IC's manufacturer

    I dood it . . . . .in my interpreting it as best as I could, with it using a NON CONTRASTING foil pattern of two shades of green . . . further
    impacted upon, with both sub par edge lighting and glaring central light reflections.'

    Thanks for the component identification, helps greatly.

    And apologies for the poor photo quality.
     
  17. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    'TRY THIS ONE . . . .

    Take your pulled original . . .HIGHLY likely .. . being a metal film resistor and jump its two ends together and connect to one of the leads of an ohmmeter set to low scale ohms. Take a naked #11 Exacto blade and grip it in constant contact with the other ohmmeter lead and initially stab to the paired resistor leads, to confirm near zero ohms continuity.
    AND THEN . . . .you gently scrape at mid point of the resistor to just easily creep thru the conformal paint coating and then I heavily suspect an ohmic reading to appear .
    Double that resistance value and it should be right at your original resistors value.
    No workee ? then move down to the " quarter " distance portions from the ends and compute accordingly. '

    It would appear it is around 38 ohm.
     
  18. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    'The RED circled BLUE device "foil path reads" as being a line spike MOV.'

    VDR1 - S10 K320
    Out of circuit this reads >2M ohm. No way of me testing this really but its not shorted and if blown it would be obviously burnt up, I would think.
     
  19. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    'If you now have full raw DC voltage thru the primary of the power transformer to the 364's internal PWR FET, but with no developed secondary supply's DC voltage from the transformer secondary . . . . . inform us and come back for our testing of the 364 and . . . .The Rest of the Story. . . . .
    Gud . . . Day . . . .'

    PLEASE correct me if I am wrong but wouldnt the pri windings circuit need to be complete, i.e relay RL3 needs to be triggered to provide the return path to "N' - mains neutral.
     
  20. Notallbad

    Notallbad

    43
    0
    Oct 9, 2012
    'GIVE us the capacitances and voltage ratings of the two E-caps just covered . . . I now see 10's @ 400VDC listed above . . ., and ALSO, those of the nearby C23 and C22 , which must be related to filtering the output of the secondary of the power transformer, as being derived from some unviewable Schottky rectifiers.'

    C3 & C4 both 10uF 400v

    C14 100uF 16v
    C24 22uF 50v

    C22 & C23 both 470uF 35v

    2 x schottky rectifiers BZX 85C 12
     
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