Tag Archives: switch mode converter

Clothes dryer repair: AKO 742336 control unit type EDR0692XAX

Repairs of household appliances aren’t generally my field of expertise, but in some cases, it can be a very rewarding activity. Some particular models of clothes dryers (“AEG”, “Whirlpool”) common in Europe use a control board, and this is not designed up to standard. The design flaw, it renders the machine inoperative in the very sense, you can’t switch it on, and it doesn’t show anything on the display. Typically, this occurs after roughly 3 years of service….

This is the control unit:
dryer control

dryer control board

dryer control board detail

edr0692xax board

After a quick inspection, it is fully clear that the defect rests with the control board, model EDR0692XAX. Easy fix, just get a spare! Well, easy, but outrageously expensive.

ako 742336 edr0692xax

The defect, it is related to a DC switch mode regulator converting mains voltage down to some useful voltage to run the controller. This is a step-down converter, NOT mains insulated!

lmk304 application

Two dead parts were found, the LNK304 switch mode converter circuit, and a 47 Ohms resistor.

dryer control lnk304gn 47r resistor

The LNK304GN is easily found, and replaced. The resistor: WATCH OUT! This is a fusible resistor, NEVER replace with just a common resistor – it will potentially set your house on fire, when the next switch mode failure happens.
The 47 Ohm resistor, it’s a 3 Watt resistor, and the ULW3 series, available from all major suppliers, should be a good replacement.

ulw3 fusible resistor

This is the failure charcteristics of the ULW3 resistors – it will go open circuit if overloaded, without release of any flames or particles. It a hybrid, partly fuse, partly resistor.

ulw3 fusing characteristics