Given the number of posts with topics like this one, maybe it's time to have a sticky on what you the player can do to check or fix electronic issues, and when to turn the amp over to a tech. Why? With only a description of symptoms, even the most knowledgeable people here can often only suggest possibilities (sometimes for days, and sometimes wrong) when in many cases a few minutes with decent test equipment (by these same folks) is all it would take to definitely identify the problem and its cost to repair. More importantly, it can cost a lot less to have a repair done if you go through these steps, because being a knowledgeable user and reporting what you tried to your competent tech can save them a bunch of time retracing these steps. That said, there are lots of very savvy folks and boutique and name brand amp designers hanging around TB. If you make it through the steps outlined later in this post, feel free to ask them, bearing in mind the best answer may well still be "Take it to a good tech." This post is written assuming no electronics knowledge, no test equipment, and no ability to solder electronic connections. Repliers, please try to remember this assumption when posting. Thanks. Checkout steps for amps and things connected to them 1) Is it plugged in? Check that all connections for instrument signal and power are in place and firmly seated. Some amps and pedals sound like they just blew up if an input cable is only plugged halfway in. Rack gear too. Check that the controls are all turned up to normal settings. An unlucky bump can easily make your gear appear dead or hideously overdriven. It can also affect frequency response, as those controls are just as susceptible. Make sure the AC power is plugged in and indicates good. You'd be amazed how often this one bites even the pros. Another aspect of this step is "Do I have all the right cables in all the right places?". Instrument cables plugged into speakers (bad or distorted sound) and speaker cables plugged into instruments (lots of hum and noise) are the big ones here. 2) Do I have the right lights? If you're supposed to have them, no lights = no power. Momentary lights may indicate a dead battery, wall wart, or amp protection kicking in. Overload and Clip lights (when available) lit up all the time are a Bad Thing and often mean a trip to the tech. If you find a blown fuse or tripped circuit breaker, it is often worth a try to replace or reset it ONCE. Repeated occurrences indicate something more serious, even if it is as simple as a defective circuit breaker. Take that as "Something needs to change or be fixed". Overloading your AC power feed is something to check out here - try a different circuit than the rest of the band. It might help. With tube amps, lights have an extra meaning. Are all the tubes lit up? Can you tap any tubes and get ugly noises? Bad tubes or dirty sockets could be the cause. See 3). 3) Is everything clean? Dirty connections can kill, and not in the Good Way. Distortion, loss of signal, hum, noise, and bad tone can all be caused by dirt. Have a can of decent contact cleaner in your kit, like Caig DeoxIT(tm). The local Radio Shack will have something if the commercial grade stuff is unavailable. Most pots have a small opening you can squirt the stuff into. Move the pot back and forth, or plug and unplug to cycle jacks and plugs and work the cleaner into hard to reach spots. If nothing else is available, you can use denatured alcohol on many contacts in a pinch. Be careful, as it can melt some plastics. Be very careful if you are a cotton swab fan. Those fibers can get loose and cause more trouble than you had when you started. An amp full of dust bunnies, pack rat or squirrel nests, old sandwiches, baggies, or the like is trouble waiting to happen. Cooling fans will suck any junk floating in the air into your amp. Periodically clean any dust, dirt, or other grunge out of your amp's innards. It'll run much happier and cooler. Which brings us to... 4) Is the fan running? If your amp has a fan, it ought to run sometimes. If it never does, you'll eventually cook its innards. Have it replaced ASAP for long and happy amp life. Dead fans can cause well designed amps to go into thermal shutdown to save themselves, an important symptom. 5) That Kind of Smoke is a Bad Thing. You can ignore it, and try again, but it really is rare that everything just goes on Happily Ever After. More often, more smoke is released and more damage is done. 6) Am I SURE it's not something else? Dying batteries or preamps in instruments with active electronics, bad wiring, dead/dirty pots, jacks, or pickups in all instruments, bad signal cables, blown speakers, broken or dead pedals, wireless links. All of these can fail in ways that make it sound like your amp's soul was just taken away to the heavens. Substitute another known good instrument or signal source (a mic can be handy here). Substitute another known good cable. Substitute a known good cable for the wireless link. Try fresh batteries. Take the pedals out of the signal chain. Go direct or passive when you have bypass switching. Swap out pedals one at a time if necessary. Spare tubes are good to have around, even if they are your old pulls. At worst, you know how they sounded when you pulled them. Check for blown speakers. A cardboard tube from a roll of paper towels is really handy for checking individual drivers in a cabinet. Be careful not to injure your hearing. 7) Did I actually do all this stuff? Really. Make sure you did. Take your time. Don't embarrass yourself. Generally, if you've made it this far and you're still out of luck, it could be time for a trip to your tech. Make sure you let them know the things you have tried already; you'll save them some time and yourself some money. If you still feel the need to post a query, you'll save 80% of the irrelevant answers if you list what you already tried. This is just a start. Please feel free to add any other tips which have helped you.