left speaker not working.

[robertod]

I switched the input cable from left to right and now the left speaker works and the right speaker does not.
What should I check out next... Maybe something in the pre-amp, idk.
Thanks
I switched left and right phono cables no help. 
Checking tubes on wright audio pre amp.  Might be a tube.  waiting for system to cool.
*System cooled, two tubes out, replaced.
*System up and running.
**Solved**