ARZ853H control board circuit.

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  • March 18, 2017 at 4:18 pm #90853
    supremetwo
    Participant

    Hi, All

    Anyone have the control board circuit diagram for Whirlpool fridge-freezer ARZ853H ?

    I have fault-found so far that the relay coil voltage is around half the 24v dc that it should be.

    Removed and tested the relay and it works fine with 24v dc applied.

    Regards,

    Malcolm

    March 18, 2017 at 4:49 pm #446224
    electrofix
    Moderator

    Re: ARZ853H control board circuit.

    circuit diagram of the whole unit could maybe be obtained but you want the circuit diagram of the pcb not a hope

    post pictures of both sides of the board and i will see if there is anything i can spot. please be careful they are in focus as i will have to enlarge them to look around

    Dave

    March 19, 2017 at 6:52 pm #446225
    supremetwo
    Participant

    Re: ARZ853H control board circuit.

    Hi, Dave

    Thanks

    I already have the circuit of the appliance.

    No obvious sign such as a burned component.

    I’ve now scanned the PCB and am in the process of id’ing the components and drawing the circuit.

    I suspect that a diode is down in one half of the bridge that feeds the compressor relay coil.

    Malcolm

    March 19, 2017 at 10:58 pm #446226
    electrofix
    Moderator

    Re: ARZ853H control board circuit.

    cant see why they would have a bridge rec feeding a relay coil unless there is a separate supply just for it , but that would mean using opto isolators from the main circuit
    more likely is the power supply to the whole board faulty and below voltage

    Dave

    March 23, 2017 at 5:08 pm #446227
    supremetwo
    Participant

    Re: ARZ853H control board circuit.

    Hi, Dave

    The zener diodes are part of the bridge 2x12v plus 1x 5v seems about right for a 24v relay coil.

    I replaced the 100uf capacitor but still around 13v at the coil, though its enough to operate the relay now. But the cap was from some old stock in my bits box – I’ve ordered new ones and diodes.

    Board picture and component details (pdf):-

    https://www.dropbox.com/s/l5il1w6ff95sl … d.pdf?dl=0

    Malcolm

    March 23, 2017 at 5:33 pm #446228
    electrofix
    Moderator

    Re: ARZ853H control board circuit.

    well if your circuit diag is correct you have a zenner across the output + and – and that will stop the voltage at 12v as far as i can make out
    you also have a diode short circuiting the power in and that sounds wrong

    also they never operate relays at the correct voltage to stop coil heating and failure. would expect a voltage lower than 18v

    think i can see it now . the .68uF (C6) cap is acting as a dropper (capacitive reactance) change it

    Dave

    March 23, 2017 at 7:23 pm #446229
    supremetwo
    Participant

    Re: ARZ853H control board circuit.

    There are two 12v zeners in series d22 and d23.

    Thanks for the .68uF suggestion – that was low on my suspect list.

    However, I’m now getting 13.4 volts at the relay coil so I’ll try a new 100uF first and see if that gets closer to your suggested 18 volts.

    The rest of the circuit seems fine with fridge and freezer temperatures as set.

    Malcolm

    March 23, 2017 at 9:26 pm #446230
    electrofix
    Moderator

    Re: ARZ853H control board circuit.

    I see now you have 2 12v zenners in one leg

    makes sense now resistor r22 does 2 jobs stops in rush current and will be a fusible resistor in case C6 fails
    c6 is used as a voltage dropper on a 50 hz supply will have a resistance of 4680 ohms. r23 at 680k is only there to discharge C6 when supply is turned off

    d1 is there to half wave supply as voltage can only enter circuit on the +ve half cycle. voltage is then controlled by the zenners and smoothed by the cap

    can only summize why zd21 is there. I assume they pick off the 5V supply across it to supply one of the chips

    still think .68 is likely gone down in value leading to higher resistance and therefore less power

    Dave

    April 3, 2017 at 2:51 pm #446231
    supremetwo
    Participant

    Re: ARZ853H control board circuit.

    electrofix wrote:also they never operate relays at the correct voltage to stop coil heating and failure. would expect a voltage lower than 18v

    think i can see it now . the .68uF (C6) cap is acting as a dropper (capacitive reactance) change it Dave

    Dave,

    Spot on with the .68uF – changed that and the relay coil volts went up from 13.3v to 20.9v.

    Thanks so much for pointing me in that direction.

    Regards,

    Malcolm

    April 3, 2017 at 3:07 pm #446232
    electrofix
    Moderator

    Re: ARZ853H control board circuit.

    no probs glad you got it sorted

    Dave

    April 4, 2017 at 3:14 pm #446233
    supremetwo
    Participant

    Re: ARZ853H control board circuit.

    The basic circuit turns out to be ‘Capacitative half wave rectification post-zener’ with the added complication of dual outputs.

    Presume it’s common for the control boards of this type of appliance?

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