I HAD A PROBLEM WITH MY AMP ON a gig recently that ended up being caused by a bad preamp tube. I didn’t have any spare tubes with me or even any fuses, and after struggling to get through the night with a borrowed amp, I vowed to put together a gig first aid kit. What should I put in it? —RC via email
You wouldn’t drive across the country without a spare tire and some jumper cables, so you should be just as prepared when you go to your gig. Here is what I’d recommend you put in your kit:
1) Speaker Cable. If you play a combo amp, you may not need it, but with a head/cabinet setup a spare is essential.
2) Guitar Cable. Something could happen to cause your cable to fail, so always pack an extra.
3) Guitar Strings
4) String winder
5) Wire cutters
6) Needle-nose pliers
7) Phillips screwdriver
8) Flathead screwdriver
9) Extra set of power tubes. If your amp uses a pair, buy four. That will leave you with an extra set. You simply bias your amp with the first pair, and since the second pair already matches the first, there’s no need to rebias when changing to the second pair
10) Extra preamp tubes of each kind that your amp uses. If it has all 12AX7s, pack one or two extra. If it has a 12AT7, bring one of those too. You don’t need a full set, just one or two of each kind.
11) Extra rectifier tube or solid-state rectifier substitute that plugs into the same socket.
12) Fuses. Make sure they are Slo-Blo and have the correct amperage and voltage rating. Remove the fuse from your amp and take it to Radio Shack to match it exactly, then buy a box of five for spares.
13) Flashlight. You may need it on a dark stage.
14) 9-volt batteries. If you use pedals you might want several of these. Even if you use a power supply, batteries are good insurance in case something goes wrong with it.
If your amp isn’t producing sound when you flip the standby switch to the “on” position, turn it off immediately and check to see if the speaker is connected. It’s easy to forget to connect an amp head to the speaker cabinet, and when a guitar signal is put through a tube amp without a speaker load connected to it, the tube sockets and the output transformer could arc, causing major damage.
If the speaker cable is connected, turn on the amp but don’t play—just listen closely for hiss or other signs that the speaker is getting signal. Once you are sure the speaker is connected, check your guitar cable and any other audio cables to make sure the amp is actually getting signal. Once you’ve determined that the problem is not with the cables, then go back to the amp and start looking for things like a blown fuse and/or a bad tube.