Location of heatsink question?

[RobBozic]

Hi guys,

I've about to add a fixed bias VVR3 to my amp which is built on a 5E3 steel chassis, it's fairly cramped but the mosfet is going to be mounted in between the OT / screen filter caps & the PI. I'm going to install a heatsink to make sure the mosfet doesn't overheat, however is the location of the heatsink critical? Should it be located near the mosfet (obviously on the outside of the chassis) or can it can anywhere on the chassis.

Thanks in advance
Rob

[sluckey]

Mount the MOSFET directly on the heatsink for maximum heat transfer. Steel is not a good heatsink.

[PRR]

> Should it be located near the mosfet

ON the MOSFET!!

Or -- I burned my finger on the solder iron. I get some ice to cool it. Should the ice be "near" my finger? Yes, ON my finger, or it don't do a darn thing.

Get the heat OUT of the MOSFET into something (a heatsink) which will spread out the heat into a large volume of air.

Inside or outside the chassis is a secondary issue. Outside is probably better cooling. You can extend the wires any reasonable length. However this device has 400V on it. It must NOT be touchable. The old TO-3 plastic covers are hard to find and never abuse-proof. I'd be inclined to go into the coolest corner inside the chassis.

[RobBozic]

Thanks guys.

There isn't any room inside the chassis to put the heatsink, I'm going to have to locate it externally between the PT & OT. I'm going to buy the largest one I can physically fit in there.

I'll put some pictures up when I get home from work today.

Rob