KLP1 and K5581 Has a Speaker Channel Down

[JohnG]

I,m so rusty when it comes to thinking about the basic investigations to identify a cause of the loss of the Speaker channel.
I have just set up the KLP1 and K5881, for the first time in a very long time.
I have little confidence in believing my swapping cables is showing the cause of the lost channel.
Could a kindness be offered in supplying a sequence of tests that would help isolate the failing component.
I am not a multimeter/soldering iron using type of person, so I am hoping to be able to identify the component in need of a visit to a local cleverer person than I
Looking forward to kicking myself, when I start recalling some of the advice offered.