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Failed MOSFET in switch mode power supply for an audio mixer

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Lostfollicles

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Hi

I have a failed MDF4N65B 4 amp mosfet in a SMPS powering a Mackie ProFX12 v2 audio mixer that seemed to fail when there was a power cut even though the SMPS looks like it has more than adequate mains spike protection and no other damaged components that I can tell/see, all caps look good but will test before new mosfet install, however I suspect the device is under rated for it's purpose.

My question is: Should I use the same 4 amp mosfet and adapt better cooling or upgrade it if possible with the MDF7N65B which is a 7 amp device?

If the 7 amp mosfet could be used as an upgrade would the running temperature of the 7 amp mosfet be lower than the 4 amp mosfet? The reason I ask is that the mixer has to work in higher temperatures than normal here in Spain so it would benefit from a lower temperature device.

From the specs of the 7 amp mosfet it looks very similar apart from the turn on and turn off times or am I missing the bigger picture here?

I would appreciate any help and thank you in advance!

Please see attached PDF's
 

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  • MDF4N65BTH datasheet.pdf
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  • MDF7N65B datasheet.pdf
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Hi,

The information provided is so little. Please tell us more about the SMPS and also how it was selected for powering the mixer.

It seems like it was bought off the shelf. In order to provide adequate information easily I would say you should post links to documentations for both the SMPS and the mixer.
 
Hi,

The information provided is so little. Please tell us more about the SMPS and also how it was selected for powering the mixer.

It seems like it was bought off the shelf. In order to provide adequate information easily I would say you should post links to documentations for both the SMPS and the mixer.

Hi Akanimo
Yes it was is a Mackie ProFXv2 Mixer

Please find pictures of the unit plus power supply removed from unit. ProFX12v2 MOSFET side.JPGProFX12v2 PCB side.JPGProFX12v2 Top side.JPGProFXv2 gut shot.jpgProFXv2 Front shot.jpg
 

more heatsinking - or a fan ( perhaps small internal one ) are good ideas ....
 

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