Why do tubes glow

Lots of blue glow means the bias is too high. If you can't monitor the current into the tubes look at the power supply ripple. If the bias is adjustable, lower it a bit and see if the glow drops and if it sounds fine. One fellow around here had blue glow and bought new output tubes to shortly afterwards buying a new power transformer.

Bad cap! I have seen this in my tubes and I view it as a good sign - the vacuum has to be good for a blue glow. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.

Find More Posts by Bigun. I do have some new tubes that I could put in to see if the glow is tube related or topology related as mentioned. Tubes test fine on a decent tester for GM, gas, shorts. My initial thought was that these tubes are high in hours but the comments posted thus far don't really support that notion. So I'll do a tube swap and move the tubes to another amp and see how they behave.

I've seen this blue glow in the fuel pond at Sizewell B. Is it radiation or just the underwater lamps? Well, to be more precise, Cerenkov radiation. Purely because blowing cool air on your tubes, means they will have to work harder to maintain their operating temperature.

Because you will crack the glass right? Trying to quickly cool extremely hot tubes can strain the glass, weakening them which will more likely cause a leak within the sealed vacuum causing them to die a leaky death.

The reality is that the amp will have been designed to withstand the heat for most situations: bedroom playing, rehearsing and performing on a humid, sweaty, stage at some death metal gig for example. With that said, I would recommend a fan for the amp facing at a degree angle just not directly in front of the tubes. The main reason why tubes get a little too hot is they have either too much power are too much voltage running through or a combination of both. Keep in mind, that the heat coming from the amp can be from other components, not just the tubes.

However, if you feel that they are raging hotter than usual, take them to your local amp tech to give them a look over. Some tube worshippers will replace them every two years, whereas, others will only replace their current tubes until they die an honorable death. Over time and usage, however, the sound begins to slowly degrade and is not as crisp and sharp as it used to be.

The change may have been that slow and gradual you may have not even noticed with your ears adapting to the current tone? A full fresh power tube replacement will inevitably give your amp a new lease of life upgrading the tone similar to when you first purchased it. So how long will your tubes last until they bypass their optimal function? The point is when you feel the sound and tone is not dynamic as it used to be then a fresh tube change is on the cards.

The main thing to listen for is your amps bass response, level of punch and drive. All these factors will make the bottom-end sound lose and muddy which is usually a clear sign your power tubes need replacing.

It is also important to check the visual signs of wear and tear on your power and preamp tubes as stated above not just audible signs. Another reason why you will want to replace your tubes is they will inevitably burn out, blow or fail depending on the reliability of the amp and individual tubes. With that said, I do recommend you sample many different pre and power tube combinations with your amp as your budget can possibly afford. The reason being that you will find a combination that suits the sound of your amplifier and tones you want to achieve.

Of course, if there is another underlying issue, it may take a bit more effort to remedy. Tube amps are extremely high voltage and they are truly complex. Get help if you find yourself asking questions like, are tube amps supposed to glow?

Is it normal for a tube to glow orange? Is it normal for a tube to glow blue? The color of the glow will depend on the gases used to fill the tubes. Great explanation. One point of confusion. The getter is there to improve the vacuum after the tube has been evacuated and sealed, and to handle expected outgassing from the tube elements over the life of the tube. Still tubing after all these years—the power amplifier stage in my homemade everyday-use transmitter uses a 12GT5; its driver is a If the amp can be biased, and you know how to bias amps safely, I suggest you do it.

Aim for 30mA to 40mA per tube is likely fine. Blue glow is not an issue, we have another blog article that addresses this. McIntosh and a few other amp manufacturers install LEDs into the sockets that then shine up though the bottom of the tube to create those coloured glows.