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

[Enrico Lazzerini]

Dear All,
I wish to update about my work. I received finally a couple of LB1620 from
Arizona. Italian custom got them for a lot of time. Well I desoldered it
from the pcb and I checked between +24vdc and ground for not have any
shortcircuit. Good thing. I algo put away the circuit with a resistor and a
zener diode and insert a new 7809 ic to give a good power of 9vdc to pins:
19,9 and 12 of the lb1620. powering with +24vdc the spindle motor its not
rotate. As you can see from the its pics from here: 
https://www.dropbox.com/sh/p12w71v69tjgfz7/AAAIReql4Se5ZCkLClPoAVOPa?dl=0
there is a tirdh input pin in the connector: what is it use? Is goes to pin5
of the C358C as input of the operational IC. On each pin of the engine I
misured a +4,6 vdc respect to the gnd. 
I have also a scope but what have I to checK?

Thanks so much for any suggestion.

Enrico