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

Brent Hilpert hilpert at
Mon Mar 2 14:58:06 CST 2015

On 2015-Mar-02, at 7:50 AM, tony duell wrote:
	Lazzerini wrote:
>> +24vdc to R112 and the D102 Zener that is saved so from here to pins: 19, 2
>> and 12 of the LB1620 then it continue to pin 16 of the TC9142P.

The D102-zener-regulated supply, in addition to supplying the 1620 & 9142, appears to supply that other 8-pin chip, and the hall-effect sensors.

>> The datasheet of this last one say that the power voltage would be between
>> 5Vdc and 9,5Vdc. So would this say that the zenere has to be from
>> 5 to 9 vdc? Have i to measure the exact voltage on pin 16 of the TC9142P
>> without the  LB1620 and how have i to expect?
> Yes. Connect up the 24V supply now and measure the voltage across the zener D102. It 
> should be, I guess ,between 5V and 9.5V. 

The 1620 min Vcc2 was 8.5V, so with the max 9.5V of the 9142, it looks like the zener is supposed to be 9V (9.1V).

>> The LB1620 is smoked. What other components must be tested to ensure
>> that the new LB1620 can not be broken just fitted?
> Check that zener voltage. If that's OK, it is very likely nothing will damage the new IC.

One concern is that if the zener is incorrect and too high a V, and the short in the 1620 was pulling that V down, the shorted 1620 may have been saving the other semiconductors. Powering it up with the 1620 now removed might apply high V to the other semis, so it would be an idea to isolate them for testing the zener voltage, or remove the zener for out-of-circuit checking (apply a voltage to it though a series R).

I'm just going by your writing in one of the photos that it's a 15V zener - how did you know that or come to write it?

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