Hi,
Here's a Imax B+ battery charger, but the fan has stopped, so it overheats.

Can anyone identify the ? component and tell me how to test what I think are mosfets, shown on the pc
C

 

The ? item appears to be a diode, probably for back EMF protection from the fan?
The MOSFET to the left seems to be the one feeding the fan socket (maybe). The only sure way to test it is to remove it, though you could check voltages at the gate and drain/source (depending if it is P or N channel). There may not be voltages other than gate if the power is fed through the fan first, then down to the MOSFET.

 

The ? item appears to be a diode, probably for back EMF protection from the fan?
The MOSFET to the left seems to be the one feeding the fan socket (maybe). The only sure way to test it is to remove it, though you could check voltages at the gate and drain/source (depending if it is P or N channel). There may not be voltages other than gate if the power is fed through the fan first, then down to the MOSFET.

Hi S,
Once lefty has been removed, how do I test it please?
C

 

Hi S,
Once lefty has been removed, how do I test it please?
C

I would check the voltages first on the gate and drain.
Are you sure the fan is good?

 

I would check the voltages first on the gate and drain.
Are you sure the fan is good?
View attachment 371149

I would check the voltages first on the gate and drain.
Are you sure the fan is good?
View attachment 371149

Hi S2,
Good point.
Do you know how to test a removed mosfet?
C

 

The voltage readings should tell if it needs replacement.
Have you verified the Fan is OK?

 

Without the fan plugged in, there may not be any voltage on the drain (as pictured). Plug the fan in and measure the gate and drain voltages first, before removing the mosfet.

 

Hi All,
The fan didn't work!
A different larger (working) fan didn't work!
If you look at the top image 2nd power transistor? in, there's a little wire attached to the heatsink part with white silicon, I assume this should be heated to get the fan to work, and the left pin show 1V, the right pin showed 15V.

The are other historic faults on the pcb, so 'that's it' dump!!

Thanks for trying.
C