Not just an replacement, but an improvement!

Guarantee Conditions

Uploaded: 11-Dez-2014



12 months or 2000 hours whatever comes first

with online registration:

      1. 18 months or 2500 hours whatever comes first.
      2. Five years guarantee in case of gas, bad getter, bad vacuum, or a loose tube base.
Have you bought new EML Tubes? Then you can register here for extended guarantee.


Defect rate

If a new electron tube has a build in defect, it will probably occur within the first few hundred hours of use. To give an example: micro cracks in the glass, will not give a problem during storage, but will give a vacuum defect after appr. 200 hours. When a tube will stay good for this time, you can expect a vacuum defect will not develop at all. For many other defects there is the same situation. 

Safe operation

With all tubes, regardless the brand, high Anode dissipation, or high current, will result in lower lifetime. The safe operation area is below 75...80% of maximum Anode dissipation, and "long life" application is around 60% of maximum. In some cases, a tube can be used at maximum power, and lifetime is still maximized as well. With such tubes it can be seen in the data sheet, when the typical dissipation and maximum dissipation is the same number. For instance with a tube like 2A3 this is the case, wheras with 300B this is not so.


The best lifetime will occur at the specified heater voltage, a safe electrical circuit, and no oversized capacitors. The Anode current is factory tested after the burn-in, and when the tube has become stabile. This level is called 100% when the tube is new. This is an individual value for each tube, and the required Control Grid Voltage for this is written on the tube box. If you wan to judge the condition of an older tube, you should test it at just that same Control Grid Voltage, as we measured when the tube was new. It will stay at or close to that level during customer burn in. In the beginning the Anode current can change (up or down) very slowly, or stabilize for most of the time. After it stabilizes, the customer burn in is finished, and normal wear out will start to begin. You will observe the Anode current going down very slow, each few hundred hours. So if the Anode current (referring to the original test value) has decreased, this is a normal sign of use, and no defect. This will continue during the entire lifetime. Amplifiers with Auto bias, will hold the Anode current fairly good. Amplifiers with adjustable bias, will need regularly adjustment. That's what the adjustment is for, because these have no Auto bias. When the end of lifetime is getting nearer, the Anode current will start to go down quicker than before. Generally, you can say when the tubes sound good, that's what they are. Only you can not judge the remaining lifetime in the tube by that. On a test bench, the measured values of fairly used tubes can be at 70% Anode current. There is a general conception that such tubes have still enough lifetime left in, to make a well designed amplifier function normally. This value of 70% is found on most tube testers as the level where the "good" reading begins.

End of Lifetime

This can be heard when the tube starts to distort at loud music, and was not doing so before. When you can measure the Anode current, the area for a "good" tube is above 70%. Below this is not always the end of lifetime, or a bad tube. Tubes with values of 40% have been reported to work normal, depending on the amplifier. Below 40% problems will probably occur. So you can feel safe when buying used tubes at or above 70%. Not below that. 

1) This is what we give guarantee on:

      1. The factory test data is guaranteed to repeat when you receive new tubes. Sample Picture
      2. All specified parameters, and the good sound of the tube
      3. Gas development, the getter flash, or anything else related to bad vacuum
      4. All mechanical issues, like filament breakage, loose contacts inside, loose tube base, etc.

2) Seller Guarantee Period:

12 months or 2000 hours whatever comes first


3) Manufacturer Guarantee Period, with online registration.

      1. 18 months or 2500 hours whatever comes first.
      2. Five years guarantee in case of gas, bad getter, bad vacuum, or a loose tube base.

4) Guarantee Conditions:

      1. With postal shipment, the guarantee begins with the date of receival
      2. The lifetime guarantee is for tubes under typical operating conditions
      3. The guarantee is to the first owner only
      4. The guarantee in the first year is by the tube seller.
      5. The guarantee after the first year, is by Emission Labs ®directly.
      6. Online registration must be done within 4 weeks after receival
      7. When a tube is replaced, the original guarantee start date will stay unchanged
      8. A copy of the original invoice must be available upon request
      9. When the failure reason is unclear, we may require a copy of the amplifier circuit diagram

5) Additional costs:

When we have to replace used defective tubes by factory new tubes, this is an advantage for the user. For this we must charge something. When shipping tubes, the buyer and the seller each pay their own shipment cost.

      1. We replace free of charges within the first three months
      2. We charge 10% of the actual list price from 4....12 months
      3. We charge 40% of the actual list price from 13 months, until the end of the 5th year.
      4. A loose tube base is repaired free of charge during the entire guarantee period

6) This is what we do not give guarantee on:

      1. Tubes operated above the maximum specifications (No exceptions)
      2. Tubes used at too low or too high heater voltage (max +/-5%)
      3. Tubes that have been cryogenically treated
      4. Glass breakage caused by the user
      5. Tubes not burned-in by the instructions. (Instructions are in tubes box)
      6. Tubes used with electronic circuits for filament heating or Anode current control, which we have not approved. Do not buy our tubes, if you disagree with this point. More about it here
      7. Tubes with serialized filaments. More about it here
      8. Tubes that are used in particular amplifiers, for which we not recommend to use our tubes. More about it here
      9. Paper-in-oil coupling capacitors are made for industrial conditions, with extreme overload. These may all suddenly develop small leakage, which can come and go at any time. Testing such a capacitor for low leakage means nothing, because leakage will disappear again. These should NEVER be used in a low leakage application, as this is the one thing they are not made for. Spontaneous leakage increases the tube bias severely, and burn down the tube unexpectedly. Use of Paper-Oil capacitors voids the guarantee always. (No exceptions)
      10. Tubes showing a spark at switch on or off. This is an amplifier problem, which may be solved. More about it here
      11. Tubes with mechanical damage, not reported directly after receival.
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