19 Feb
2010
19 Feb
'10
8:49 p.m.
Chris Elmquist wrote:
OK, that's clearly a supply line filter.
WHat I would do to trace it is to remove the inductor (temporarily) and
then trace fro mthe +ve side of the capacitor to anything that might need
12V (spindle motor, stepper motor, head load solenoid, read amplifer).
See which of those go to the +e side of the capacito, and which go
directly to the 12V input.
On the Siemens drives also used in the H89 and
H17, there is an inductor
in series with the +12 to the spindle motor. It's a hash choke that keeps
the motor noise from going back into the +12 rail. When the grease in
the spindle motor gets old and sticky, the motor draws way too much current
at startup (if it ever does start spinning) and toasts this inductor.
I don't have "real" schematics for the drive and I have not
had time yet to work out the whole circuit but what I do know
is that one side of the inductor is connected to +12. The
simple diagram would be:
+12----<inductor>---+---<tantalum cap>----ground
|
|
somewhere else
not yet traced
When the tantalum cap shorted, burned and popped, the inductor
was carrying +12 to ground. That's how it got "toasty".
OK, so at least there's a reason why it overheated.
-tony