Amp Power Light Changing Intensity

Have been having an issue for some time with my blue LED power light on my Coincident Dynamo 34SE Mk1 tube ampm. At times it is glowing with full intensity, other times the glow is barely visible and from time to time it changes intensity during play. Cannot really tell if there is an audible difference in sound but could this point out to a fault in the amp or is it just the last legs of the LED which I should try and change?