Preamp output very weak

[gerryt]

I am attempting to repair a Yorkville KW100 (schematic attached). When I plug a music source into the return input which goes directly to the power amplifer section of the unit I get a clear loud musical output from the speaker. However when I plug the same music source into input channel one I get no output, and when I plug the same music source into channel two I get a very quiet output with the volume control for channel two turned up all the way. It is a weak signal but it is not distorted. I have replaced the op amp for channel two (U1 in the schematic) and tested the volume control for channel to be sure it is not faulty. I am a beginner in electronics repair and would appreciate any insights as to why I am getting such a weak signal from the pre amp into the power amp.

 

[Bluejets]

why I am getting such a weak signal from the pre amp into the power amp

Possibly overdriven the input with (not specified) whatever signal input you used.
Possibly damaged components.

tested the volume control for channel to be sure it is not faulty

again, no idea what you did here.......

When I plug a music source into the return input

You supplied a circuit diagram and then use your own terminology so no one has any idea what you plugged in where.

 

[gerryt]

Possibly overdriven the input with (not specified) whatever signal input you used.
Possibly damaged components.

again, no idea what you did here.......

You supplied a circuit diagram and then use your own terminology so no one has any idea what you plugged in where.

Yes, I agree, I was not very clear about what I did, so I will attempt to describe with greater clarity. Played music from my CD player headphone output using a TRS 1/4" input into JB7 (return) Sound that resulted was loud and clear. Plugged same cable with same CD player source into JB3 and JB4 and turned 5B Volume 2 to full volume. Result is a barely audible but undistorted sound output.

 

[Bluejets]

Yes, I agree, I was not very clear about what I did, so I will attempt to describe with greater clarity. Played music from my CD player headphone output using a TRS 1/4" input into JB7 (return) Sound that resulted was loud and clear. Plugged same cable with same CD player source into JB3 and JB4 and turned 5B Volume 2 to full volume. Result is a barely audible but undistorted sound output.

......and did you notice the recommended input level ..???
What is your signal level..........???

 

[sgodblacktechy]

check connections, components around U1, and for any damage.