TideLog Posts Tagged “big pop”

Hoover washer dryers used to be synonymous with quality and could go 10 years plus without issues, but now they just seem to be dropping dead left right and centre when really young. In the space of one day today I’ve both had a Hoover engineer come out to my parent’s machine, for a motor replacement under Hoover warranty, and later that day I myself was called out to fix another Hoover washer dryer, both the same model, different faults.

WDYN856DG

The patient was a 2 year old WDYN856 DG washer/dryer, with no signs of life, except clicking noises, following a loud bang during a dry cycle. Clicking relays are usually always main control unit failure, so myself and Martin, my repair assistant, got to work. There was no other life from the programme selector dial, LED segment display unit, buttons, or their LED’s, apart from the clicking. We pulled the control unit out, it looked fine from within its casing, but once unclipped from it, we saw the catastrophic damage:

Hoover-WDYN856DG-control-unit-PCB-in-shieldHoover-WDYN856DG-control-unit-PCB

Can you guess where the actual brain of that massive washing machine is? Nope, none of the big components! That tiny chip that I’ve circled in red is the computer of the machine, smaller than a two-pence piece! The rest of the board is just power regulation, the control relays, and the outputs for the motor and element, plus all the connectors for sensors. The two small plugs on the very right-middle are the programming headers for programming the EEPROM. You can see the giant ferrite inductor coil, and those big heatsinks? That’s the transistor & Triac that control the motor speed, they act as an inverter and tacho control. The higher the switching frequency of those transistors, the faster the motor spins. They get mad hot, and very stressed, especially the massive transistor to the right of the coil.

Unfortunately, as you can see from the picture, around where the microcontroller is, that is where the failure has occurred. The area is all burnt, and has catastrophically shorted. The yellow highlight on the left is also where some damage to a diode, resistor and capacitor has occurred. The damage is actually worse than it looks in the picture.

We had to replace the motor, and the front-end option selection button unit as they were unresponsive even with a new control unit. We can’t be sure of the exact cause, but we suspect the motor has shorted, and as it’s directly wired to the transistors, has caused a massive short circuit, taking out the control unit and the option selection button unit (which itself had microcontrollers on it, but these were visually undamaged).

Unfortunately you can’t just buy a new control unit and connect it up, the EEPROM needs to be programmed with machine specific code, the machine will just flash an EEPROM communication error otherwise. We had the Hoover engineer programmer, so were OK 😉

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