The idea I think is you use cotton gloves to keep oil off the tubes. I stopped doing this years ago because I preferred the grip you got by using bare hands. You can wipe the 'oils' off with a cotton cloth if it bothers you. Personally I don't think it makes any meaningful difference.
Can you touch the tubes?
I was talking to someone at the tube store about replacing some KT 150 tubes and he said it was perfectly fine to touch the tubes.
I've always thought you're supposed to handle these things very carefully with white gloves or a microfiber cloth.
Handling them with my fingers makes it easier to pull them out , insert them more securely.
Does it really matter if my fingerprints get on the glass or should I clean them off with a microfiber cloth after I touch them?
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I suspect the white glove thing ties back to someone with a bad case of OCD and a good imagination. I've worked with tube gear for over 50 years now -- building, repairing and using -- and never had a problem handling tubes with my hands. No tube failure ever from that, and no appearance issues. Tubes are made of glass, and yes, glass can get dirty, but one can also clean glass. The only time I've ever used a cloth is if the tube needs to be handled while still hot. You don't want to burn your fingers. |
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It’s funny how all us audiophiles are so skittish about tubes. Any of you older guitarists or bass players remember the abuse everyone gave to those Ampeg, Sunn, Marshalls. Throwing them down in the back of trucks and car trunks. I don’t remember anyone ever even think about the tubes. I don’t remember one tube ever breaking. Then again, memory of those days are a bit foggy for some reason. |
If a tube has a separate base, you pull and push it in by that base to prevent separation of the base from the glass envelope. But there is NO need to be concerned about oil being deposited on the glass. That concern comes from what happens to some types of light bulbs. Oil deposited on the glass of such bulbs carbonizes from the intense heat. That black spot will absorb light from the bulb, rather than letting the light pass through, and this causes that spot to heat up so much that the glass fails, which causes it to explode. This kind of heat an light production never occurs with audio tubes. |
For some amps it's difficult to use the base of a tube to push and pull into socket. I found if I just grip it comfortably around the upper portion of the tube and rock it back-and-forth while applying pressure as it slides in. Of course there's always a fear the glass will shatter but I spread the distribution of my fingers which I think reduces the risk. If you try to squeeze an egg in your hand with a lot of pressure it won't break but if you start angling your fingers into the egg it will break. I'm not gonna try this with a tube. if The tube shatters who knows what happens at that point aside from losing 50 to 100 bucks on the tube and debris field. |
I believe this train of thought comes from warnings on head light bulbs in the auto industry. Quote: When changing the headlight, highbeam or foglight bulb on your vehicle, it is of paramount importance that you not touch the glass part of the bulb with your bare fingers. Oils on you hands will cause the section of the bulb that you touched to get much hotter than other areas of the bulb and will lead to the bulb burning out much quicker. If you do happen to touch the glass part of the bulb, take a solvent like rubbing alcohol and clean the globe thoroughly before installing it in your vehicle. This will remove the oil and the unwanted hotspots. |
Wash your hands 1st will minimize oil and give you a better grip. If you can, avoid touching the identifying markings on the glass. If you do, lack of oil will be beneficial. Whether base or not, use the lower hand for the lifting force, and the other hand on the top, applying any needed minimal movement to help the pins slide up. The bases are glued on, to give you something to grab/lift. they are no part of the vacuum seal of the glass. The glass may also be broken, a separate issue. If a base becomes loose or partially loose, the tube may be fine. IOW, you still have a working unit. Then you are faced with the decision: buy a pair or quad pair of matched tubes, and keep the loose base as a spare if needed, so you are not without music. btw, tube testers usually have a few size tube pin straighteners. |
For those of you who would still rather wear gloves to pull tubes, these are perfect. A pair came with my PrimaLuna amp. They have gripper 'dots' on the thumb and fingers for a nice positive grip on the tube. I use them even though I agree with most responders that it isn't necessary for tube protection. I just like having a secure grip on the tube when changing one.
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If a base is loose, even completely free of the glass envelope, as long as the wires are not cut, you can glue the base and glass together. I use high temperature epoxy, but I have no idea if that is the best glue to use. It is not that common for the base to come loose unless a tube is really old. I run 70-80 year old tubes so I am careful. Some not so old Western Electric 300B reissues had weak glue joints so care is needed. I have never heard of anyone squeezing or pinching a tube so hard as to shatter the glass, but I suppose that is possible. Aside from dropping a tube, the most common accident is inserting a tube incorrectly so that the pins are in the wrong holes. That can happen if the key on the central post, or the post itself is broken off so thar a tube can be inserted even when incorrectly oriented. Some 4-pin tubes, like 300Bs, don’t even have a key and rely on two of the pins being fatter; unfortunately, they are not fat enough that they cannot be shoved into the small hole of most tube bases so that a horrible accident is possible. |
If you look through tube manuals under Installation and Application the only things stated are the socket pin counts and whether or not the tube can be mounted in any position. Since "touching the glass" is not stated (or "do not touch if they glow") you can assume it's something too obvious to print. |
Hello Emerging Soul! The idea comes from the era when quartz mini bulbs (which run very hot) were introduced. Often found in desk lamps, the tiny bulbs almost instantly heat up to way past boiling water temperatures. Fingerprints leave oil on the surface. It takes time for the oil to heat up and that part of the "bulb" will heat up slower than the rest of the lamp. As all the bulb is trying to expand (slightly) as it heats, the slower heating parts will cause such a stress that the bulb may shatterl It will happen very quickly and the users hand will be in the vicinity as very sharp, very hot fragments of "quartz" will be sprayed about. This is a real problem with projector bulbs. I have replaced many such bulbs without problems, but I always leave them in the plastic bags they come in (after cuting off the bottom of the bag) when inserting them. Then, I just slip the bag off the bulb before applying power. Ordinary vacuum tubes are glass "bottles" that don't run nearly as hot and heat up gradually. Cleanliness and care are always a good idea, however. |
Transistors was just coming into television sets when I started into electronics. The only time we did not grab a tube with our bare finger was when it was hot. We then used a cloth, napkin, paper towel... Couple funny story now. Wasn't then. There were two tubes in the high voltage section in a tv that were in a metal cage/s. The Regulator tube sometimes had a gripper or holder at the base. We had to push down on the gripper to remove the tube. You could only get one hand into the cage. I remove the tube's anode cap. Reach in, push down on the grippers with fingers and wiggle the tube up and out. There is a point where the tube pins become exposed but are still connected. I think it was a Zenith. The picture tube anode was connected to the cathode of the regulator. My fingers took one for the cause. Yes, I did discharge the picture tube. But the voltage creeps back. On the larger 25, 27 inch tubes, they creep back with a vengeance. The post above mentioned Halogen lamps. Well, I got into Copy Machines after tv repair. They used to use Halogen lamps. About 1/4 inch round, 12" long. 950 to 1250 watts. They fail in two ways. Filament breaks, not light. Or they get air in them, blackening the inside of the bulb. e.g., get light but not enough = dark copies. I could get to that lamp in a minute. Well, the lamp goes 1000 degrees in a second. Takes about 5 minutes to cool down to touch. Melting skin is like grease on that glass tube.
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You want to avoid the oils which in turn heat up the glass and make the tubes hotter than they should be. If it's unavoidable use isopropyl (rubbing) alcohol to clean off the glass. The little alcohol cleaning wipes are really handy for spot cleaning like that. Of course, make sure your gear is off before getting any fluid anywhere near it. :) |
Washing your hands before (and in the following case after) is a good idea. https://www.udiscovermusic.com/wp-content/uploads/2020/04/Tubes-GettyImages-102677143.jpg
DeKay |
@facten I guess you were just being a smart ass but here is some data: Normal power tubes, 200 to 300 deg F Incandescent light bulb 400 deg F 845 tube 500 to 600 deg F halogen bulb 1000 to 1200 deg F Because the the extreme temps of the halogen bulbs, differential heating caused by oils can cause the bulb to break. I've never heard of an 845 breaking from this. jerry |
Since Halogen was brought up, I’ll tell you my experience with 400 watt Metal Halide for Office Lighting. I designed Corporate Office Space for a living. I was an early adopter and specifier of Furniture Mounted Indirect Lighting for Office Cubies. Very efficient, no reflections of ceiling light fixtures in computer screens, indirect light (bounced off ceilings) light from several directions minimized shadows. Total watts needed for large space far lower than using ceiling fluorescent. Important because many buildings AC systems were already overloaded by then new computers everywhere! Reduce that Lighting Load! Used them for many clients, including IBM, JP Stevens, CBS several subsidiaries, Time Life, Fortune Magazine, Many Insurance Companies, Lawyers ... The fixtures had tempered glass covers, lamps had to be replaced, I found out several clients either left the glass covers off, or replaced them with non-tempered glass. GE issued a bulletin years after they promoted these for office use: these lamps may experience ’non-passive’ end of life (another member mentioned ’non-passive above). I called GE, what the hell does non-passive mean? Oh, well, the lamp can explode, blasting broken glass up to 2,700 degrees in all directions. Any other questions? And yes Dorothy, if you got/left any finger oil on them, they could/would explode. Holy Crap: these fixtures were typically located at the intersection of 4 cubies. I issued my own bulletin to all clients: explained the ’non-passive’ to clients, scared them as best I could, and made it perfectly clear that ALL of these fixtures MUST have their Tempered Glass Covers properly installed and secure. The outer glass may be ONLY 800F degrees, the inner glass typically 2,000F, a failure, up to 2,700F I never specified them again.
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I had metal halide bulbs over s fish tank. The fixture had a safety glass. When a bulb exploded (near its end of life, a common occurrence) a few glass fragments were so hot they fused with the safety glass. I’ve also had tv projector bulbs explode (also metal halide). As I explained above, failure from skin oil happens with such bulbs because the oil carbonizes from the heat, turns black, and the black absorbs the high intensity light instead of letting the light pass through, and it is this additional heating from absorbing the light that causes failure. Even if a carbonized black spot did develop on a tube, it doesn’t give off enough light to cause overheating; the tube will NEVER fail this way. I’ve seen tubes marked by permanent markers; there is no harm from this. |
I don't believe that these audio tubes get anywhere near hot enough to degrade the glass envelope. I think this common belief is a holdover from high temp bulbs such as quartz- iodine light bulbs, Xenon flashtubes or old type M flashbulbs (anyone else out there old enough to remember flashbulbs?). Some of these bulbs get hot enough for the glass wrapper to glow. I still wipe my tubes down with an alcohol wipe anyway because I think it's a good habit with no basis in fact. Then I can feel good about myself when I watch these expensive things glow. |
