Well, great to be with you, here in this fantastic Forum. I'm fortunate to have an old but very good audio equipment, not in the top class, but enough for me. A couple of JBL Monitor Studio 4412 with a JVC AX-Z911BK amplifier, both buy it in 1989. Also I have CD player HD7525 from Harman Kardon, and a cassette player from Technics that I don't use now, M63 with three heads. Well, 20 years ago I repaired my amplifier only changing the 8 power transistors. Now on, again is broken. I try test it only 4 of them, the good ones, but the Relay never switches on. I see the service manual in the troubleshooting, but, my question is: Is this amplifier works on well only with 4 transistors, or needs the 8? I know that maybe obviously the answer is yes, but...The keys to search the trouble are to see components that are far away from the power PCB, so, that's strange and for that, I ask you to all of you, if you know the right answer. Thanks. Miquel Tuset, from Barcelona, Catalonia, Spain, a Jazz Lover!