Fuses and confusion

If you bought gear NEW from a reputable manufacturer/dealer network, your warranty will be fine. If you didn’t--oops!
Sure are a lot of void warranties in our group if you can't even open it up. All those interior amp pics on the web are of out-of-warranty amps.
Hilarious!

Funny stuff. Don’t open that lid to change a fuse or tube or you will void warranty? You must be kidding right? Oh my. 

Some vendors may well void a warranty if the gear is opened up.

If you modify internals yourself, even just replacing a fuse, there is an even better chance warranty will be affected.

People should always check their warranties (if in effect) to see what conditions apply. It’s only common sense.

Vendors can’t afford to give customers a free pass to make changes then come running if a problem under warranty. It is usually not part of the deal!

Do not listen to anyone who just says "do it", no caveats, with gear under warranty. That is bad advice There may or may not be a problem.

If the fuse you put in is found to be the issue should a warranty repair ever be needed, then that is yet another story. It’s part of the risk you take.

Change a blown fuse or an older tube? Yes you can with no warranty worries. These things are owner replaceable and not meant to only be sent back to the manufacturer. 

People should always check their warranties (if in effect) to see what conditions apply. It’s only common sense.