Quick Answer: How Can You Tell If A Vacuum Tube Is Bad?

How do I know when my tubes need replacing?

A: These are the most common signs that tubes need replacement: Excessive noise (hiss, hum) including squealing or microphonic tubes.

Loss of high end.

A muddy bottom end; Sounds like there is too much bass and note clarity is lost.

Erratic changes in the overall volume.

The amp doesn’t work!.

How do you test a 12ax7 tube?

Well, while the amp is on, try tapping the tubes with a pencil. If you hear the tapping through the speaker, then replace the tube, it’s microphonic.

Why do vacuum tubes fail?

By far the most common fault with vacuum tube rectifiers is that the cathode will lose emission,so that the internal voltage drop of the device will increase to the point where they become unusable. Occasionally,you will get a filament go open circuit,but that is a lot rarer,arc overs internally are extremely rare.

When should I replace vacuum tubes?

A simple guide is to replace the power tubes twice as often as the preamp tubes, because they wear out more quickly. An amp that is used every day should expect to replace its power tubes every one or two years. If you notice lower output, strange noises, or a “muddier” tone, your tubes probably need replacing.

Why do vacuum tubes glow blue?

A tube that is glowing blue is often wrongly perceived as a defect, however, it’s really just a side effect of a power tube — a fluorescent glow in the blue spectrum. The tube is fine! It actually indicates that the vacuum inside the tube is very good, which is what allows this phenomenon to occur.

Do all tube amps hiss?

Not all tube amps are like that, but yes some have a fair level of background hum and/or hiss. It’s also a function of how you use the amp and what you plug into it. If you have a darker sounding guitar and crank up the treble, well hiss be yours. Some pedals will also provide a significant amount of hiss.

How long does a vacuum tube last?

about 5,000 to 10,000 hoursDepending on how often you turn on and turn off your gear, but tubes should last about 5,000 to 10,000 hours. For most people, they only need to be replaced every 2-3 years at most. But it’s good to have at least a spare set around just in case one of them decides to die on you.

What does a bad tube sound like?

Preamp Tubes. Preamp tubes usually cause problems through noise or microphonics. If noise, you will hear hiss, crackling, popping or similar issues. If you hear squeal, hum or feedback, it is typically a microphonic tube. Noise from microphonic tubes will typically increase with a volume increase.

Are amp tubes supposed to glow?

A: That blue glow is just a side effect of a power tube — a fluorescent glow in the blue spectrum. The tube is fine! It actually indicates that the vacuum inside the tube is very good, which is what allows this phenomenon to occur. It will not have any effect on the performance or tone of the amp.

Do all vacuum tubes glow?

5 Answers. You can use AC or DC voltage to power the filament of a vacuum tube. The filament will glow when powered up which is what you are referring to as “lighting up”. … Most tubes that were used in radio and television sets used either 6 or 12 volts although many other voltages were used.

Can bad preamp tubes cause volume loss?

Use the wooden part to tap each of the preamp tubes and main power tubes. A good tube will be a dead ‘thud’ sound, so if you hear one that has a high ringing rattling sound, that’s the bad tube. Bad tubes will make volume drop and tone sounds will be dulled. When a tube goes bad, this is exactly what happens.

How often should preamp tubes be replaced?

You should replace them when they are dead. *There is no set rule for how long they last, but in general, they last longer than power tubes. *Maybe twice as long or better life expectancy for power tubes. *They are also self-biasing of course, so don’t be afraid to change them yourself.

How much does it cost to replace tubes in an amp?

EL84 aren’t much more. If you just get run of the mill stuff it will be cheap. Once you start looking into NOS tubes, etc, you can expect to pay $25-200 per tube in some cases.

Are vacuum tubes dangerous?

These types of tubes are readily discerned by a competent trained health physicist, and are not a significant radiation danger, but they are a factor of 10 to 200 times higher than normal background radiation.

Do vacuum tubes wear out?

Eventually the silvery coating turns white, and you know the tube is bad. … Sometimes they lasted only 6 months, whereas a low power tube could last for 20 years or more. Even if they degraded they were still usable. The oldest vacuum tubes had pure tungsten filaments, without any coating, so they didn’t degrade.

How long does a 12ax7 tube last?

about 10,000 hoursSmall signal tubes like a 12AX7 or 6922 will work well on average for about 10,000 hours. If you leave your equipment on 24 hours a day, well you do the math: There are 8,760 hours in a year.

Are tube amps really better?

Tube amplifiers sound better because of the euphonic distortions they add to the music, as well as plenty of other reasons I’ll cover below. … The ways that tubes distort when pushed to the edge are much more musical than the artificial sounds that come from transistor amplifiers when overdriven.

How much are old radio tubes worth?

These numbers include 101D ($400+) and 205D ($300+). Other WE tubes include VT1 ($200+) and VT-2/205A ($150+). Any early vacuum tube with a “tip” (the little glass nub on the top) and a brass base has some value to collectors even if it’s just usable for display.

How long do 6h30 tubes last?

10,000 hoursAnd having said all of that, the 6H30 has supposedly been rated at 10,000 hours of life. If you increase the heater voltage above the rated spec, you will greatly diminish the cathode life.

Is it bad to leave a tube amp on for a long time?

There is nothing wrong with leaving on your amp for a long time. It doesn’t wear out the tubes faster than if you were to play it for eight hours straight. Probably even less, because you don’t actually play it, but just leave it. Imagine how long before a show the equipment will be standing on stage, ready to play.

How do I know if my amp tubes are bad?

Symptoms of Bad Pre and Power TubesUnusual sounds coming from the amp..(‘popping’ ‘hissing’ ‘crackling’ ‘humming’)The amps overall volume lower than usual.Individual tubes glowing brighter or dimmer than others.The amp’s tone has degraded (loss of tonal dynamics)The amp will not power on.