Hi All:
Okay, so the question about what drives the current for the reactor control
winding. Here we go .... BOSS Service Manual p4-76
Looking at Figure 1040215, it can be seen that the emitters of the drive
transistors are returned to ground through resistors R1 and R2. A voltage
proportional to motor current is developed across these resistors and fed to
the ACC input at pins 9, 35, and 34. Looking at just the X-axis portion, see
that a portion of the apmplifiger Q5-Q4, where it is compared to the voltage
across the two forwrd-biased diodes D19 and D20. When it exceeds the diode
voltage Q5 will start to turn on and Q4 to turn off. This loweres the base
voltage of the PNP transistor Q3, turning it on and pulling up the base of Q2.
Q2 now turns on and pulls the base of Q22 down, turning it off and Q1 with it.
Q1 controls the DC through the control winding of the saturable reactor;
turning if off stops the control current and causes the pmpedance of the power
winding to increase greatly.
I think this is where I'll start probing tomorrow. Thanks for pointing me in
this direction guys, it does look like it could cause my problem. But I'm happy
to see that the saturation control current is not under CPU control ... that's
good because I have not taken any steps to control it. And it also means my
memory is still somewhat sound.
Thanks All.
More as it develops.
Andrew
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