Question about Cary V12 amplifiers

I purchased a pre-owned Cary V12R stereo amplifier (recently re-tubed). It sounds and looks great. One of the 'good health' LEDs for a pair of output tubes on the left channel, however, is no longer lit. The tubes appear fine, and I don't notice any sound degradation. Before I adjust bias or purchase tubes, does anyone have any comments or suggestions?
change pairs with a known good pair from the right channel and see if the LED re-lights on the left side and goes off on the right channel.
Have a look and see if the wire to the led has not come loose. Mine came loose a few times and all I had to do is stick it back.

Appreciate you sharing your findings.I also have a V12 and have had this problem,however in my case it was the slow blow fuse.Having said that you never know what suprises await down the road.