"SeventhPrince???" wrote in message
oups.com...
Hi,

Any advice on how come when a particular transistor when soldered gives
out different readings as compared to when it has been desoldered and
taken out.

When desoldered and taken out from pcb, gives good readings indicating
the transistor is good. However when on board, it gives inconsistent
readings showing the transistor is bad.

End of day, is the transistor good or bad? Thanks.

Am using analog multimeter under the diode function for checking on
transistors.Thanks.

SeventhPrince???


While in-circuit, you are measuring resistances or other current pathways
which are in the transistor circuit under test. Out-of-circuit you are
measuring the transistor characteristics alone. If it tests good
out-of-circuit, it's "good", meaning it isn't shorted, open, etc. That is
not, however, necessarily the same thing as saying it's still within design
specs. If a transistor has been stressed by some failure elsewhere in the
circuit, it can in fact be pushed out of tolerance (e.g., gain suffers).
Most often, though, when subjected to such catastrophic stresses they just
develop opens or shorts.