Good Day,
Quote: - I'm thinking Q872 and the other 2 transistors are OK.? There's just not quite enough base current to turn on Q872, and the others.? The collector of Q860 is only 2 volts.? It should be about 52V when things are normal (+50V supply + drops of 3 transistors' B-E junctions).
Ah, yes - of course - you are raising a good point here Jimmy.? Plus some small drop across R875, of course. Too obvious. I should not try to understand voltage readings and schematics when it's getting late....
David, simply follow Jimmy's advice.? As your - 50V DC voltage reads off, you also might want to check if Q908 is on and Q909 is off during operation. See the description on page 4-30.
By the way: I have just seen that Tektronix has followed their own, good tradition and they have use sockets for all small transistors on the 7603's A11 Low Level Regulator board hardware. That should make any potential replacement work or tests easy, if necessary.
Cheers,
Magnus
