[time-nuts] HP10811-60111 oven failure + repair

Frank Stellmach frank.stellmach at freenet.de
Fri Oct 21 12:41:35 EDT 2011


Hello Achim,

nice pictures, how to access the thermal fuse, thankys for sharing.

Sorry to say, but a poly-/multifuse is the totally wrong component for 
this purpose.
It will neither help on overcurrent, nor on overheating.

The trip current (where MF opens) will be ca. 3A @ 23°C, and ca. 1.5A @ 
85°C, where the oven is running normally.
I've taken these data from BOURNS MF-R type, should apply also to your 
special component.

Datasheets end at 85°C, so I estimate that thermal derating of the MF 
would perhaps give about 750mA @ 145°C which also does not shut down 
further heating, but will for sure damage permamently all internal 
soldering junctions.

Therefore, a regular thermal fuse (max. 105°C type) will ease your mind 
better, than this shunt.

Frank




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