19 Jun
2013
19 Jun
'13
1:39 p.m.
The spindle motor rotates easily, but when I apply
power, it tries to
turn on, moves just a bit (like the magnetic field is pulling to some
state) and then stops. A bit later, something turns something off
(there is a slight click), and that's all there is.
Do you mean that the motor turns through a very small angle (<< 1
revolutuion)?
If so, this soulds like a program with the motor controller circuitry.
These motors are electornically commuatated using power transsitors on
the logic bvoard.
If this is the same ST225 that I've jsut dug out a scheamtic for, the
motor controlelr IC is an 8 pin custom hign at lcoation U10 on the PCB.
It takes a 2MHz clock (taken from the microcontroller crystal) at pin 1
and a signal fro ma hall sesor i nthe drive motor on pin 3. Pins 6 and 7
drive a pair of 2N6039 power transistors to drive the centre-tapepd
widing. associated with thsoe are a pair of BD436 transistors used for
braking and a further 2 transstor (2N3906 and BD436) circuti to apply 12V
to the centre-tap of the winding.
I think I'd start by checkign those power transisotrs. If that doesn't
help, look at the signals on the pins of U10
Unless that motor changes speed, I would think the controller would be
simplistic, and thus the issue is the motor itself. If, though, there
is more to the controller (it seems to have quite a few wires going into
it), then maybe a portion of the controller circuit is bad. Swapping
(not to start a flame fest) would quickly determine one or the other, it
seems.
The spindle motor in the scheamtic in front of me has 6 wires. the pinout
of J4 on the logic PCB (where hte motor conencts to) is :
Hall Sensor Pulse
Ground
+5V
Motor winding centre tap
One end of the motor winding
Polarising key
Other end of the motor winding
It should be fairly easy to check the widnig nfor continuity and to look
at the hall sensor output while turnig nthe motor by hand with power applied.
-tony