Re: Purpose of Q32 in S-52


Albert Otten
 

If the -12.4 V supply is lost, the comparator/S-H stops working, and the
amplifier goes open-loop, to whatever maximum current it can deliver, possibly
risking overheating the TD. In this event, Q32 forces the current into ground
instead.
Hi Ed,
When -12 V is lost, U30B will not conduct and the base of Q72 will have the proper voltage for comparator operation, like in period 2. Hence I think the TD current will not get higher than Ip. As soon as the TD fires the comparator switches Q74 to on and the TD current will drop below the arming current. The voltage at the now isolated base of Q90 will slowly drop. After that different scenarios can be thought of. The comparator may or may not switch back. The danger I think is that the average power might get too large.
Albert

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