Factory Warranty Conditions
February 2007 

Each pair comes with a certificate with the matching data on it.
Sample:  Diodes  - Triodes

Defect rate

If a new electron tube has a build in defect,  it will probably occur within the first few hundred  hours of use, in the guarantee time. To give an example: microcracks 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 this tube will never develop a vacuum defect at all. For many other defects there is the same situation. 

Safe operation

The lifetime of electron tubes depends mostly on the use conditions. Maximum power use, or any attemps to do it better than what is normal since 60 years, will result in less lifetime. The safe operation area is below 75...80% of maximum plate dissipation, and "long life" applications are around 60% of maximum dissipation.

Lifetime

The  best lifetime is coming with the specified filament voltage, plain normal tube use, and no oversized components, like too large capacitors. The plate 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. So it is an individual value for each tube, and the required grid voltage for this is written on the tube box. It will stay at or close to that level during customer burn in. In the beginning the plate 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 plate current going down very slow, each few hundred hours. So if the plate current (referring to the original test value) has decreased, this is just a sign of use, and no defect. This will continue during the lifetime. Amplifiers with Autobias, will hold the plate current fairly good. Amplifiers with adjustable bias, will need regularly adjustment. That's what the adjustment is for, because these have no Autobias. When the end of lifetime is getting nearer, the plate 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% and the tubes can still be considered "good" with still sufficient lifetime left in it.

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 plate current, the area, where you can say a tube is "good" is above 70%. Below this is not always the end of lifetime. Tubes with values of 40% can sound normal, depending on the amplifier. Below 40% problems will probably occur. You can feel safe when buying used tubes at or above 70%. Not below that. 

This is what we give guarantee on:

      1. The guarantee is for tubes under typical operating conditions
      2. All specified parameters,  tube vacuum, and and the good sound  of the tube
      3. All mechanical issues, like filament breakage, loose contacts inside, socket defects, etc.

Guarantee Conditions:

      1. The guarantee is for a period of 12 months or 2000 hours, whatever comes first
      2. The guarantee starts with the official invoice date
      3. The guarantee is given by the official dealer, and is to the first owner only
      4. When a tube is replaced, the original guarantee start date will stay unchanged
      5. The tube owner will ship defective tubes free of cost
      6. A copy of the invoice must be send with the tubes
      7. When the failure reason of a tube is unclear, we require a copy of the amplifier circuit diagram

    Additional costs:

When we 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 sender each pays his own shipment cost.
      1. We replace free of charges within the first three months
      2. We charge 10% of the actual list price after three months
      3. We charge 15% of the actual list price after six months
      4. We charge 25% of the actual list price after nine months
    This is what we do not give guarantee on:
      1. Tubes operated above the maximum specifications (No exceptions)
      2. Tubes  not burned-in  by the instructions. (Instructions are in tubes box)
      3. Tubes operated from a constant current source for the filament heating, or with series resistors in the filament path, or any other circuits that slow down heating up of the filaments
      4. Coupling capacittors are paper-in-oil typ. This voids guarantee allways. Tubes showing a spark at switch on or off. This is an amplifier problem. Check here for more info
      5. Tubes with visible signs of damage,  not reported directly after receival
      6. Low hum of aging  tubes, using loudspeakers above 100dBm
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