At 11:21 AM 1/1/2003, Karl von Salzen wrote:
>I looked at your pics......
>I am at a loss seeing the 'obvious almost burned thru' power transister. Can
>you put an arrow in one of the pics pointing to it?

At the bottom left of the main board in the first picture there is a
good-sized resistor that has obviously gotten pretty hot.  This may or may
not be normal  to the beast, though I suspect that if the designers had
expected that much heat they would have mounted the resistor higher off the
board.

There's a greenish device in a TO-220-type case mounted vertically near the
bottom right -- it could be a transistor or a voltage regulator.  No
obvious damage though it probably wouldn't show in that view even if there
was.  And semiconductor devices can and do fail with no visible external signs.

A first thing to try in many cases is to simply reflow the solder on all
connections on the board -- it's astonishing how many things are fixed this
way, particularly in devices subjected to vibration or thermal
cycling.  The faulty joint if there is one will likely not be visible
except through a microscope (stereo dissecting-type works well if you have
access).  Also when epoxy-dipped tantalum capacitors short and fail they
often squirt a tiny streak of metal through an almost invisible pinhole in
the case.  The splash will end up somewhere in the area with one end
pointing toward the offender, and if you're really lucky there may be a
*tiny* drop of metal on the outside of the capacitor case.  I don't see any
such caps on that board, just general info.  Also, a faded ID stamp on a
transistor or IC may indicate overheating -- especially if it's faded in
the middle of the IC and not the edges.

cheers
david

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"