#2
You can visually check for redplating:

or sonic problems such as major volume fluctuations on all channels, no sound at all and such other similar situations.

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[quote="'[BurnTheDusk"]']Boss pedals may be built like tanks but I would rather buy a cardboard box that is on my side than pay for a tank that is working against me.
#3
Reduced output
More noise than you usually get
Increased warm-up times

Those are the ones I've encountered.
Quote by Marty Friedman
Because I bend in such an unorthodox fashion; the notes kinda slide up and slide down...
#4
hmm, what about the appearance of the tube?
Ibanez 2570
Blackstar HT-5 Stack
Digtech GNX3
Dunlop Crybaby Classic
#5
Quote by toshiyap
hmm, what about the appearance of the tube?


usually difficult to tell by just looking at the tube...because tubes can discolor and still be fine. But the red plating in the first post is a good sign of a failing tube (or other component failure as well).