Bosch Tumble Dryer WTV74105GB/16 no POWER

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  • March 20, 2023 at 2:33 pm #101811
    nicneff
    Participant

    Hi,

    I have a Bosch WTV74105GB/16 Tumble Dryer.

    Without warning the machine does not display any signs of power.

    No smells noises or anything. It’s about 10 years old.

    I’ve checked the fuse etc and there is 240v going to the control panel.

    I’ve checked the door switch and there is continuity through it when closed.

    I’ve removed the control panel pcb and there are no signs of overheating or dodgy caps.

    Had a bit of a Google and there’s not too much info most of it pointing to TNY266GN ic.

    Has anyone any ideas on this, any tests I can carry out etc.

    Thanks Nick

    March 20, 2023 at 9:05 pm #486257
    electrofix
    Moderator

    look for a low value resistor. fairly big one in relation to anything else. will be under 100 ohms and often green but not always. find it and test it

    its job is to act as both a fuse and to stop high currents flowing on switch on

    if it has gone change it but make sure ait a fusible resistor of the correct value and 3 watt

    if it has gone also change the power chip like TNY but check the number on yours

    Dave

    March 21, 2023 at 11:03 am #486258
    nicneff
    Participant

    Thanks for that tip Dave, I’ll check that resistor. I’ve taken a punt and ordered the TNY266GN. I’ll post results

    March 21, 2023 at 4:58 pm #486259
    electrofix
    Moderator

    have you checked the chip on your board is TYN266GN ?

    when these chips fail the resistor goes to about 95{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} of the time

    Dave

    March 21, 2023 at 7:26 pm #486260
    nicneff
    Participant

    Yes I’ve checked,the chip is a TNY266GN. I have checked that resistor and it’s ok, measures 50 ohm so is only 3 out of spec.
    got that chip coming Thursday so I’ll swap it out and hope for the best. Got my doubts though

    March 21, 2023 at 10:23 pm #486261
    electrofix
    Moderator

    well its either
    1 no power to board
    2 power chip gone
    3 other chip on board gone

    be careful there is 300v DC on main input caps

    the chips have a fold back circuit. if there is a short on the board the chips will turn off the power and then turn it on again slowly to see if the short is still there.

    if you measure the voltage on the low voltage caps as the board is powered it should be a steady voltage. if its rising and falling again up down up down etc then you can say the chip is ok but the board has gone
    if you have no voltage at all then its poss chip

    Dave

    March 22, 2023 at 10:15 am #486262
    nicneff
    Participant

    Thanks Dave that is very helpful. I’ll make these tests before and after I replace the power chip

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