How to save two Mitsubishi M2896 drive (spindle motor smoked!)

[Brent Hilpert]

On 2015-Mar-18, at 2:05 PM, Enrico Lazzerini wrote:
> I tried to connect a resistor of 10kohm to 3rd wire of the connector but
> putting it to ground or to +5vdc nothing happens. I also checked if with a
> disk inserted into the drive what kind of signal come out from the 3rd wire
> from the main but always remains at zero volts. Checking with the
> oscilloscope signals on chips of the spindle motor all seems very stop and
> static. I report below some value of voltages misured on the IC's pin and
> photos at high resolution at the link below.
> 
> https://www.dropbox.com/sh/ozy5mn06hyz9jn1/AADelz2vVsTSEAwmwoVzvwppa?dl=0 

This directory is currently empty, at least as I see it here.


> LB1620
> Pin1= 18,2V
> Pin2= 9,2V
> Pin3=0V
> Pin4=24v
> Pin5=pin6=pin7=0V
> Pin8=0V
> Pin9=pin19=8,93V
> 
> TC9142P
> pin1= pin5= Q101Base=3,52v
> pin4= pin10= pin16=8,93v
> pin6=6,2v
> pin7=pin8=3,5v
> pin9= NC =3,52v
> pin11= Q101collector = 8,97v
> pin12= pin13= NC
> pin14= pin15= square wave
> 
> C358C
> pin1=pin2=pin3= 4,5v
> pin4=GND
> pin5=0,5v connected to the 3rd input wire
> pin6= 1,2v connected to the r101 - r105 with the other side of r101
> connected to pin 16 of 9142
> pin7= 7,76v connected to Q101 collector
> pin8= 9v

Haven't been through them thoroughly yet but most of these look sensible.

Presence of the square wave on (TC9142)pin14,15 is a good sign, that's the reference oscillator, and suggests the 9142 may be OK.

- Observe (C358)pin7 while alternating the 0/+5 test voltage on the 3rd connector pin, pin 7 should change accordingly to 0V & 9V. Similarly (LB1620)pin11 should be changing.

- The hall sensors may still be suspect. They are supplied by being stacked in series with two resistors, one each in the ground leg side and +9V supply side. First thing to do would be to measure the V on the two supply pins of each hall sensor (the pins closer to the motor center).  The supply voltage should divided between the 3 sensors and 2 resistors. 

The halls sensors feed the LB1620 with a differential drive from each sensor to avoid having to make a fixed GND reference, which allowed them to be stacked in series for the supply. In theory you would be able to observe a change on one of the drive pair of each sensor with the scope as you manually rotate the rotor but the change may be too small to observe within the bias from the stacked supply. Properly one would use two scope channels in A-B difference mode to observe the drive pair.

- Instead, or in addition, you might try watching the (LB1620)pins1,2,3 outputs while spinning the rotor manually to see if they change.


> main link with other info
> https://www.dropbox.com/sh/p12w71v69tjgfz7/AAAIReql4Se5ZCkLClPoAVOPa?dl=0