On Dec 29, 5:09*am, "N_Cook" wrote:
Those white ceramic cased ones about 3 watt in the form of a rectangular
block 15x5x12mm . No cracks in the ceramic but white powder laying around
some of them.
eg 6 power transistors in "parallel", one has a lot of powder around it on
the pcb, one has some around it and the other 4 are clean. No fan air
directed in that area to blow anything away. Both have the powder deposited
not along the long sides but at the end away from any possible heat radiated
from the transitor/ heatsink, perhaps just coincidence. Can anything be
inferred from these deposits/ associated transistor?

I've seen failed o/c ones of this type with a crack in the casing, does it
mean the powdery ones have been overheated and will fail imminently or an
indicator that the associated transistor is taking too much of its share of
the current?

How is the resistance of the various units, within specs?