Denon avr-1913 left surround channel low and noisy

Hi, I bought a Denon avr-1913 receiver used and the left surround channel is low and noisy. I have been doing research and I'm trying to test and see if it's the output transistor, am I in the right ballpark? It's my first time working on an amp, any help or direction would be appreciated.

update: I tested all the transistors and got consistent readings on all of them (I think)

service manual: Table Of Contents - Denon AVR-1913 Service Manual [Page 2] | ManualsLib
 
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