Manrose Gold Circuit board burn out X 2

[TheBigP]

Hi,

I have a downstairs toilet with a light and manrose gold fan. The fan has a separate isolator switch outside. When the isolator is off the fan does not turn on and when the isolator is on and the light turned on the fan activates. The Manrose Gold fan has a timer on it set to about 1 minute. I can provide serial numbers if required to give exact model etc.

The problem I'm having is that the board on the fan has burnt out twice. Once on the original fan which was running without problem for 3 years and once on a replacement fan from Manrose under waranty. This waranty fan did work but only for about 10 X on and off uses.

The first burn out the board was slightly brown and the second burn out the board was similar but not as bad and appears to be greyish in colour.

Is there something I need to check or have checked on the circuit? I have checked the isolator connections and they were fine. The connections on the fan were fine. Multimeter reading were fine accross the live and the earth were fine. Is there something missing? The earth is terminaed to a block. Could this be the issue?

I'm asking the question to Manrose to see what they think but any help here would be welcome.

 

[Alec_t]

I don't have experience of that particular fan, but for a couple of other brands I've done autopsies on the issue has been the voltage-dropper resistor (the fattest one on the board) running hot. If you have space, replacing the resistor with one of the same resistance but a higher wattage rating, and mounting it well clear of the circuit board, might prolong the fan life.

 

[TheBigP]

Having been a little stuck I checked the Isolator again and the switched live was not terminated correctly! All working fine now. Thanks again.

 

[JohnW2]

I don't have experience of that particular fan, but for a couple of other brands I've done autopsies on the issue has been the voltage-dropper resistor (the fattest one on the board) running hot. If you have space, replacing the resistor with one of the same resistance but a higher wattage rating, and mounting it well clear of the circuit board, might prolong the fan life.

All true. Those resistors get very hot, not the least because they are powered 24/7. A coupleof comments:

• the hot resistor often takes out one of the adjacent electrolytic capacitors, failure of which (rather than failure of the resistor) is commonly the event that results in the fan 'failing'
• although replacing the resistor with a higher wattage one of the same value (if it will fit), will probably result in the resistor not getting quite so hot, it won't reduce the amount of heat being generated within the very confined space available, so the thermal effects on other components (particularly the capacitors) will not necessarily be all that much reduced - although one would hope for some 'benefit'.

Kind Regards, John