TEST PROCESSES / MILITARY
JAN TESTED
Q: What does JAN in front of the part number mean?
A:JAN = Joint Army Navy. The word JAN is a protected, like a trade mark. The tube factory must do a stress test (above 100% plate dissipation) on samples of standard tubes. When they survived, the whole lot is approved, and can be marked JAN-6SN7. The samples that are actually used for the stress tests must be destroyed. Auditors can show up unexpectedly to inspect the process. JAN Specs are still in use for electronics today and can apply on any electronic part. For some reason people pay no extra for JAN tested tubes, probably because they know JAN has something to do with the military, but that's all they know. Since the Army has no reputation for making better music, these tubes are not considered better. But... they are! So take the opportunity to get a JAN tube for the same price as standard tubes.
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"VT" TUBES
Q: What are "VT" tubes?
A: A mixture of just normal tubes, and some others of quality standards which or totally impossible today. The VT numbering system was made by the military, to have their own, unique part numbers. It could be plain standard tubes, or variations of normal tubes, such as another heater voltage, or some with exceptional quality. There is no general description it was related to each "VT" type, and a lot of this was secret, and communicated to vendors when ordering. So once Western Electric had set up a VT52 tube, the army would just order VT52, and purchasers could make no mistake. My experience is, these tubes are indeed of higher generic quality. Also in specific cases, there is the "as is" standard. Just as we inherited it, and specifications are not on paper. So keeping things secret, for sure worked well for the army. For instance, with VT231 what we know from observations: This is a 6SN7 if older construction, most of the time, but not always. The older type has a typical internal construction, and collectors recognise this. Now, IF it is an older type you get, this VT231 is of the best quality ever made. Most specially if it has JAN designation on it. (JAN requires a specified survival rate at an abuse situation). However, many standard 6SN7 are around, with just VT231 stamped on it by fraudulent re branders.
A positive sign is, when the plates are long, in parallel, and there is a chrome top or chrome side getter, you can't go wrong with that. Such are expensive, also when used. But there are some more real ones. |
GETTEROLOGY
Be careful with getter specialists on the forums. Real specialists are not writing BS on forums all to the day. The relation between getter appearance and tube quality in many cases is not there at all. It is like a doctor, estimating your health condition from the color of your cheeks. The following may help you to judge the getter better.
Q: Can I recognize good vacuum by the getter?
A: No you can not. The getter can look nice, when there is already some gas.
Q: Can I recognize bad vacuum by judging the getter?
A: Yes, often, but I have seen tubes with not so nice getter, and perfect vacuum, working fine.
Q: When the getter shows signs of use, is the tube bad?
A: Perhaps, but not always.
Q: When the getter is definitely bad, is the tube bad?
A: Yes.
Q: When is a getter bad?
A: A white getter is bad. Dark spots inside the getter are not relevant. Getters can be dark, or metal shiny. Both is ok. Any rings or blue colored rings inside the getter is no problem. If used tubes, it may be a sign of normal use, and no loss of emission. Or, with unused tubes it may be sign of an over heated getter in production, which is only cosmetic.
The getter is getting closer to end-of-life when the edges are sharp lines. With a good getter, the part where you can see through it is gradually starting, and can stretch over some 5mm. So there is the part where the getter is saturated, then part where it is transparent, and finally clean glass comes. So, good getters have NO sharp edges. Exceptions can be with some of the long life tubes, like RCA 5692, and some of the TESLA ECC801, ECC802, ECC803 Series. These have getters with sharper edges than normal.
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KT88
Questionable Getter
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KT88
Good getter |
This tube may work well, but a lot of the lifetime is used up. |
This tube may be good or bad. There is no way telling from the getter. |
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Q: What is SYLVANIA CHROME TOP?
A: Not only Sylvania used this, but indeed mainly it was Sylvania in the late 1930's until latest 1945. So not even for a long time. This is a version with older type of getter. So called "hot" getters. These getters do not work anymore once the tube is finished. The modern "cold" getters are active when the tube is in use, and have even limited function during storage. If you would break the glass of a chrome top, the getter will stay shiny, and gets white only after weeks. This demonstrates it's very low ability to absorb gas, when cold. By the way, chrome tops are not made with chrome, it is just shiny color. Some of the early "tall glass" tubes have this getter too, but it is flashed from the side. It is an older technology and 6SN7 like this is probably from around the 1940's. Often found in the VT231, or sometimes in 6SNTWGT.
Q: Why are CHROME TOPS better, when such a getter is not active anymore?
A: The modern (cold) getters were not invented yet. Since the "hot" getter has no function once the tube is stored or used, the manufactures were forced to use much more clean materials. The tube needed to be clean by itself, for ever. Apparently this was the much better process, and I have never yet seen a defective chrome top tube. Unfortunately, the "hot" getter process got out of use, when modern cold getters were invented. Beware: Not all tubes sold as chrome tops are actually the highly sought after "chrome" tops. Most are later technology, with a darker getter color. These are no chrome tops, but look pretty much the same. Be careful what you buy.
Q: So why are hot (Chrome color) getters not used any more, if they are better?
A: The answer is partially written above here. Also cold getters make it more convenient have messy production facilities, because these can cure any vacuum problems later. It just costs less, and yield is higher. Chrome getter tubes are often much better quality.
Click this image to see the details |
PLATOLOGY
Q: Some tubes have "powdered" gray plates, some have shiny gray plates, others have black plates. Some have even white plates. What is the difference?
A: Powdered gray plates is the latest technology. The plates are sprayed with a special paint. This only works with the later type (so called "cold") getters. Used since the 1950's, until today.
A: Alternatively, the plates can ne made of a multi layer of iron and aluminium, which automatically turns very nice and uniform grey, once heated in vacuum. However this will outgas a tiny bit. Such tubes last not as long as black plates, or powdered plates. Besides, such tubes do not like accidental overheating
A: The best coating is with Zirconium, this is also grey colored, but unfortunately not very uniform in appearance. So the surface may have some spots or stripes sometimes. However this in unbeatable quality, because Zirconium is an extremely active gettering material, provided you heat it very much, close to cherry red color. By this effect, the tube becomes resistant against accidental over heating. While during normal use Zirconium is mildly active, in addition to the normal Barium getter flash on the glass. For power tubes it is one of the best technologies ever.
Non shiny dark black plates have a carbonized surface. With this technology nothing can go wrong. Only, it produces big fat clouds of DIOXENE during production, and this process is ABSOLUTELY forbidden since decades in any country that respects human life. For those who know, for this process the poisonous "benzene" fluid is burned in a chimney , but without giving enough oxygen to it. So inside the chimney a stinking fat cloud occurs. You just hang the plate in this smoke for some minutes, and it is covered with a fat layer of black dirt. During production, when the plates are heated, the dioxin gas is set free, and pumped out of the tube. What is left is a pure carbon layer. DIOXENE and PLUTONIUM are the most poisonous materials that exist. Both will cause genetic defects, no matter how small portion you were exposed to, no matter how short. In larger doses it will cause cancer. So even if you don't get cancer from it, your children can get inherited genetic defects. In the USA and West Europe, Philips and GE stopped with it first, RCA was the last. In East Europe was still used until some years ago. The Chinese still use the process today. It works cheap, and needs no expertise. To get rid of the poisonous gas, they just open the windows of the factory. (bon apetit...)
Shiny black-grey plates. A few methods can be used to produce this coating. By treating carbonized nickel, the shiny gray Nickel-Carbide surface results from it as well. Difficult process, requiring expertise. Perfectly under control by Sylvania. Very rare with ECC81....88 types. Keep those if you find them.
White plates. These have no treatment at all. Can be shiny or opaque. Results in lower dissipation, and larger size plates, but less production steps, so less risk on contamination.
Mesh plates. Originally used because this gives higher dissipation, and uses less (expensive) tube grade nickel. The higher dissipation comes from the fact that one plate can partially radiate heat THROUGH the other one. Also the filament heat can be radiated directly through the holes. Today, this process is very difficult to repeat. Will result in fully resonance free plates. Today only made by Emission Labs. Good made mesh tubes have LONGER lifetime than standard tubes.
Semi mesh plates. Used by TJ/Fullmusic, just from nickel plate with holes in it. Process is taken from CRT mask (Color TV Tubes). Doesn't seem to give the sound advantage of real mesh, but sure looks nice. This material seems to be not ideally suited for making anodes from it, and the tubes can become gassy.
Titanium plates. No titanium, but titanium coating. A way to make the plates light gray. An interesting and very reliable coating process. |
RE-GLUE A TUBE SOCKET
Q: How can I repair that?
A1: Not with 10-seconds glue. It will come off again, dissatisfaction guaranteed. At Ebay, it seems this is what everybody is doing here. mmm ;(
A2: Not with two components glue. The temperature coefficient is not the same as glass. Sooner or later, this will break crack the glass.
A3: Original tube glue needs baking. This can not be repeated, when the glass is older than 20 years. Otherwise the glass will crack, during the baking or years later.
A4: Use the special tube repair glue from Emission Labs. This glue is magic, and can repair any tube that has some remains of the old glue inside. It partially solves the old glue, and will give no visible signs of the repair.
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BLUE GLOW
Q: Is the tube bad?
A: Mostly not.
Check here
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BURN IN
How do I burn in a new tube, and why?
Check here |
LIST OF TUBE BRANDS + LOGOS
As complete as can be. 10 pages at the moment.
Check here
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MULLARD DECODING
Q: How can I recognize if a Valvo or Philips tube was made by Mullard?
A: "Made in England" is a good sign. There is some small coding at the glass, close to the tube base. A list of these markings will be added later. Or, search for this list on: www.4tubes.com |
RE-GLUE A TUBE SOCKET
Q: How can I repair that?
A1: Not with 10-seconds glue. It will come off again, dissatisfaction guaranteed. At Ebay, it seems this is what everybody is doing here. mmm ;(
A2: Not with two components glue. The temperature coefficient is not the same as glass. At a later time, this will crack the glass, at the socket.
A3: Original tube glue. This glue must be baked. It can not be used, when the glass is older than 20 years. Otherwise the glass will crack, during the baking or years later.
A4: Use the special tube repair glue from Emission Labs. This glue is magic, and can repair any tube that has some remains of the old glue inside. It partially solves the old glue, and will give no visible signs of the repair. |
