Why do amps blow

Obviously a blown fuse will no longer allow the amp to function Once failed, a blown fuse obviously needs to be replaced but the aspiring troubleshooter must be aware that something caused the fuse to blow, it didn't just go by itself.

That something is almost always a bad power tube or rectifier tube. All tubes wear like a lightbulb or guitar strings, except over a longer period and will inevitably fail. With time the likelihood of failure increases and the same tubes that provide your favorite tones can actually pose a risk to the rest of the amp's circuitry when they fail. Understanding this concept is crucial when addressing an amp whose fuse has just blown or an amp that doesn't power up.

Let's talk about what the fuse is and does. From Wikipedia : In electronics and electrical engineering a fuse from the Latin "fusus" meaning to melt is a type of sacrificial overcurrent protection device. Its essential component is a metal wire or strip that melts when too much current flows, which interrupts the circuit in which it is connected.

In the case of tube amplifiers, when a tube shorts or fails it draws excess current. When the failed tube draws current beyond the value of the fuse, the wire in the fuse literally melts and cuts off the electricity to the amp. The amp is effectively shut off before more damage can occur. How do you like your fuse now?

The next important concept to consider when addressing a blown fuse is knowing the three things that most commonly cause a fuse to blow:. A bad power tube arcing or shorting 2. A bad rectifier tube 3. A major power surge. In the case of the first two, regular tube maintenance and general awareness of your amp and its normal operation can help you avoid many failures.

That said, tubes fail when THEY want to so there are a few further important considerations to be aware of before engaging in troubleshooting:.

It's not impossible but definitely not the norm. Whole sets of tubes do not fail. Check the amplifier fuse opening and the power wire--the correct fuse size is almost always listed. Derek Odom has freelanced since and is also an author of the macabre.

He has been published on Ches. Odom has an Associate of Arts in administration of justice. Resistance If the power wire is too small in diameter or damaged, it could cause an abundance of resistance, which creates heat, which in turn makes the amp work harder.

If you cannot see all of the wire, disconnect it from the amp and see if the fuse blows when it's inserted into the fuse holder. If it does not blow, the wire is fine and there's probably something wrong with the amplifier. With more experience, you'll be able to test for a short with an ohm meter. If the fuse in the amplifier is blowing, the problem is almost certainly in the amplifier. If the fuse is blowing as soon as power is applied to the amplifier with no power applied to the remote turn-on terminal , the amplifier likely has power supply problems.

Generally this means that the power supply FETs are shorted or the reverse protection diode is shorted. The FETs in the switching power supply generally fail when the amplifier is connected to an ohm load that's too low. If a fuse only blows AFTER the remote terminal has power applied, it's likely that the amplifier has shorted output transistors. The amplifier could also have problems like a shorted winding on the transformer or shorted rectifiers.

If the fuse only blows after the amplifier is switched on AND the volume is turned up, there could be a problem with the speakers or the speaker wiring. The reason the amp doesn't blow fuses when the volume is all of the way down is because there is no voltage on the outputs and therefore no current through the short circuit. When an amp blows a fuse or fuses, for amps with multiple fuses , you should replace the blown fuse with a fuse rated for less current.

Let's take an amp that has two 30 amp fuses. If the OEM recommended fuses blow, there is likely a serious problem. Turn off the power first before handling the wires, then find safe, out of the way spots to secure them with plastic wire ties. Blowouts caused by metal ruin the fuse if your amp has one.

Hook up working electrical cables to test the amp. Pull the RCA plug cables out from the back of the amp, then replace them with new ones. RCA cables are colored cables that easily plug into the back of the amp, but make sure the ones you get are compatible with the amp you have. Afterward, turn on the amp to see if that solves the issue. Method 4. Test the sound by unplugging the sound cables or colored RCA wires. What you hear is often as important as what you see when dealing with an unruly amp.

If the noise stops, then you know you have a wiring problem. Every device has an amperage rating that indicates what current strength it can handle. Use speakers with a similar or slightly higher rating than the amp. You may hear a lot of static or get a low-volume sound. Higher amp ratings lead to a louder, stronger sound quality. However, if the amps are more powerful than the speakers, your speakers could burn out much quicker than usual.

Go back through the wires, separating the speaker wires from the amp wires. Tuck the speaker wires into safe areas, taping them down or using plastic ties to keep them in place. When they touch, they cause the system to go silent and lose power. You can test for wire problems by moving the wires apart while the speakers and amplifier are on. Listen for the sound to come back on as you separate the wires. Stabilize the speaker enclosure to prevent rattling.

Loose speakers and subwoofers rattle in their cases as sound passes through them. If your devices have screws holding them in place, tighten the screws to prevent them from rattling. You can fix it by mounting the device to stabilize it or by turning down its settings to make it rattle less.

Connect the amp to a working pair of speakers. If your amp turns on but no sound comes out of the speakers, your overall setup may be the problem. Not all speakers are compatible with an amp. If your amp is still alive, it will respond when you connect it to speakers and other devices in good condition. Turn up the volume to see if anything changes. Radio silence from a good pair of speakers is a good sign that your amp needs to be replaced.

Method 5. Inspect the glass tubes for cracks and other signs of damage. Damaged tubes are usually very easy to spot. Plug your amp in, turn it on, and watch the tubes light up. Any tube that stays unlit or has cracks in it needs to be replaced. Milky stains inside the glass are also signs of a dead tube.

Test it in another wall outlet first. A bad power supply could be fixed by a technician in some cases. Tap the tubes with a pencil and listen for distortion. Tap the top of each tube very lightly to force it to vibrate.

Listen for the sound the vibration makes. Unusual sounds, which could be anything from simple static to the worst squeals you have ever heard, are a bad sign. Find the tube that sounds different from the others and replace it. The tubes get very hot, so cover up! Play individual notes to cause each tube to rattle as you listen for anything out of the ordinary.

Spray a contact cleaner on the tube plug to test it. Let the offending tube cool down before you pull it out of the amp. Coat the plug with a contact cleaner, then put it back into the amp. Sometimes doing this cleans out the connection, causing the tube to work again. Test it out with your guitar. You can get spray bottles full of it at most hardware stores.

You may need to pull the tube out of the socket and put it back in a few times before the cleaner affects it. Replace all of the wires to make sure they work right. Sound problems with a tube amp are typically because of the tubes, but sometimes the cables cause distortion.

Also, check the RCA wires running the speakers to make sure they are intact and plugged in. Sometimes this helps you isolate the problem to a faulty cord or connection.