SIMPLE PCB REPAIR TIPS

[kaibart]

So how do you check that the diode has gone with a meter ?

[electrofix]

all diodes will conduct in one direction.

find the diode test position on your meter

put leads on diode and notice reading

reverse leads and see if the reading is the same

if you get same reading both ways then its probably gone. to be sure unsolder 1 leg and try again. if readings are still the same replace it. Making sure the band on the component faces in the correct direction

Dave

[Jimca]

Older hotpoint ff …fridge freezer with the solenoidal capillary valve …no power to the solenoid fridge works ok freezer doesnt work at all..

220uf 35v cap on pcb mounted behind top facia .

[Hollytree_Technical]

Electrolux DW with the rear mounted main board.
Fault: Filling constantly as soon as power is turned on.

Replace Capacitor C3065, It may show as a high or low resistance on a multimeter but anything other than open ciruit is bad.

C3065 should be a 10nF 1206 capacitor, I use RS Part No: 135-6841
Capacitors C3109 and C3103 are also the same value/type and can fail in the same way but I forgot to check which outputs they control.

Jem

[electrofix]

Bosch Wan series dead

as with a lot of later machines these units have 2 power supplies built into the board. A main power supply to power everthing when the machine is running and a smaller auxilliary unit the is only there to provide power to turn the main power supply on and off. There are 2 main problems with this system. 1 the appliance will draw a small amount of power 24/7 while the unit is connected to power. 2 since its connected to power a surge on the mains can blow the power chips even when the machine is not in use. it may be consuming a very small amount to power but with millions of the machines left on its stupid

in my case its a Bosch WAN28201 unit which was completely dead. auxilliary power chip is a TNY285DG position in a really fun place under the heatsink and was covered in a varnish of somekind which was really fun to burn and scape off without board damage. To diagnose I checked and found 300Vdc in the high voltage cap but no output voltages on the low voltage ones. changed chip and am getting a constant 9v now. Hopefully will work ok once re installed

Dave

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[Hollytree_Technical]

Just to add a word of warning to Dave’s post above after having done a couple of these myself:

When this chip fails on this particular board there is no other way for the 300V cap to discharge itself so it will remain charged almost indefinatley so make sure to handle the board with extreme care till you can verify that it is no longer charged otherwise it will bite (trust me it hurts).

Jem

[washingmachinewoman]

EHO fault on AEG, Electrolux, Zanussi tumble dryer

Most of the time, this is caused by dry solder on relays, i.e. either cracked solder and/or not enough solder.
A bit of flux on connections (I used Kingbo RMA-218, which comes in a syringe with a very small nozzle for application precision), then resolder all the connections that look dodgy, adding some solder if needed. Unless you are a hawk, you’ll need some kind of magnifying device to spot the dodgy connections. I used my phone.

[electrofix]

this is a bit of an odd one but I have had the same fault twice in a week

Candy / Hoover condensor drier, syptom board completly dead or runs for 5 minutes or so and board goes dead

I suspected power chips but when i get the board back to the workshop i was getting power in and out of the power chip

I noticed a bit of corrosion and paint lifing on the board so i cleaned this carefully to stop the corrosion bridging tracks and both board started working

replaced into relavent machines and both working ok for a few weeks now

It is a board repair of sorts it just needs no parts. I suspect a bit of condensation is getting onto the board possibly because of the partly blocked condensors

Dave

[Author]

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