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发表于 2012-10-8 10:37:23
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Guitar Amplifier Tube Maintenance
How do I know if I need to change my tubes?
You probably need to change your tubes if your amplifier makes strange noises (hisses or squeals) or if it experiences a lack of power or a lack of bottom end.
My amp is making strange noises (fizzy crackling sounds or popping noises)? How do I get it fixed?
Most of the problems that we hear about with amps are due to the tubes—and are pretty straightforward to fix. Close to 90% of the problems that people call us about are due to tubes—or tube sockets. Sometimes they get dirty and mucked up. (Tubes get very hot and can burn you, of course; don’t touch them when they are hot.)
With the amp on, wiggle the tubes a little to alter the contact points. If this recreates or stops the noise, you have isolated the problem tube (or socket). If it doesn’t, turn the amp off and let the tubes cool. Then pull and reinsert each tube several times to try to establish better contact. Test the amp after you adjust each tube to see if you have found the problem.
Hopefully, this will fix the problem or determine the tube that needs to be replaced. If you have pinpointed a problem tube, but not fixed it, you probably need to replace the faulty tube.
How do I determine if my preamp tubes or my output tubes need to be changed?
If you’re experiencing a lack of bottom end and power, it’s probably your output tubes. If you’re hearing strange sounds coming from your amplifier, turn your gain section up in volume, and slowly turn the master volume down. If the noises persist after the master volume has been turned down, it’s an output tube. If the noises go away after turning the master volume down, it’s an input tube.
How often should I change my tubes?
Tubes are like light bulbs—they could go out at any time. Generally, if you’re playing hard, tube life can be anywhere from six months to a year, although we’ve seen tubes last much longer than that. Preamp tubes can last indefinitely.
Good quality tubes are the key to keeping your amplifier working great. Should you start to experience strange noises, microphonic squealing, hiss, or other strange and unwanted phenomena, check your preamp tubes. One of them may need replacement.
If strange noises do appear, unplug your guitar cord from the input to help isolate the problem and switch to the Overdrive Channel. Then, turn the Overdrive Channel’s Volume Control to ‘0.’ If the noises go away, it is likely that a preamp tube is at fault. If the noises persist, you probably have an Output tube that needs to be replaced.
What should I do to be prepared for tube problems?
You should keep a couple of good spare 12AX7 preamp tubes around at all times for any tube amplifier. This will save you a lot of trouble when you do need them. If you suspect that one of the tubes in your amp may be faulty, replace it with a known good tube and see if that alleviates the problem. If not, replace the original tube and try swapping out the next 12AX7 in the signal chain.
Beware! In certain instances, you may actually run into two microphonic tubes and have to replace them both so do not overlook this possibility. Also, just because you purchased a brand new 12AX7 does not mean that it is not microphonic. Make sure you test the tube to make sure that it is in fact good. The best way to do this—presuming you don’t have access to a tube tester—is to swap out your tubes with spares when your amp is working fine. That way, if one of the spares is faulty, you will know it immediately.
[ 本帖最后由 kldguitar 于 2012-10-8 10:42 编辑 ] |
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发表于 2012-9-24 15:37:49
，实在是太好的文章了，很有用，有两个小问题想问问：1，我每次弹琴后，关掉power后，感觉前级的管子有隐约的哒哒的声音，大概是隔十几秒一两下，持续1，2分钟那样，不知道是什么原因？2，我是用mesa的头，如果要跟换管子是否只能用回原来的型号？
