Q4 and Q5 are definitely at risk in this circuit if it is severely overdriven. Collector current of Q4 is not sufficiently limited. Looks like they’ve pulled out all the stops to maximize voltage swing on the VAS, even bootstrapping the entire + rail of the front end. Without a current limiter on Q4 it can feed a lot of base current into Q5.
thanks guys, not the easiest thing to work on. I'll need to clean up the bench area and need a couple of nasty weather days.
I'm pretty raw in this field, any clues as to what type of transistors as I have not found a parts list, I do have a large assortment of the smaller ones like Q4 & Q5 but the power transistors is what I am really looking for.
I'm pretty raw in this field, any clues as to what type of transistors as I have not found a parts list, I do have a large assortment of the smaller ones like Q4 & Q5 but the power transistors is what I am really looking for.
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