If you are considering to buy a spare VF14 for your U47, watch out!
Recently there are increasing numbers of fake VF14 offered for sale.
These two tubes were sold as "tested NOS VF14 in original boxes".
Not only that they are both not working ...
September 2009 (rough draft)
Fake VF14: These tubes look exactly like real VF14 and they usually come in original Telefunken boxes, sometimes even "sealed". Serial/batch numbers on the box correspond nicely to the numbers on the tubes. The seller offers the tube in excellent condition and often even with a "return warranty".
However, when you receive the tube, bad surprise - the "VF14" is dead. In case you are lucky and the seller reacts to your complaint at all, he will swear that it was tested ok when he sent it and will tell you that you must have killed the tube when you plugged it into your U47 (probably your faulty power supply has killed the tube, blah blah...)!
But here it comes: These tubes are in fact no VF14.
I tested some of these "fake" VF14 even before the buyer plugged them into anything and found some very disturbing facts:
Needless to say that - despite all previous warranty promises - I do not know of a single case where the seller accepted a return and refunded the purchase price. Usually the seller refuses to accept the complaint or cannot be contacted after the deal was made.
So what are these tubes?
There were several old Telefunken metal tubes like the VF14 which all look mechanically identical, the only visual difference is the type imprint on top of the tube. Even today there are relatively cheap steel tubes available, especially tubes which are not useful for anything in the audio world, like regulating tubes etc. These tubes often cost less than 10 EUR /14 USD and there are plenty around to chose from. Certainly there is some work involved to remove the original type imprint of the tube with solvent and replace it with a fake "VF14", also to organize some original blank Telefunken tube boxes and print "VF14" on them and handwrite the number. But if you keep today's market price for a NOS VF14 in its matching box in mind, it is certainly worth the effort for a reasonably skillful crook...
If you are about to buy a VF14:
If you have bought a VF14 recently and you are not sure now whether you have been cheated, do these simple tests before trying anything else:
Use an ohm-meter and test pins 5-6 (it should read about 165 Ohms). Also measure between pin 3 and the tube body (this should read 0 Ohms).
Hint: Use a needleprobe to go through the black paint of the body (a good position for this is along the flange where the metal body meets the Bakelite socket.
Not sure about the VF14 pin numbers? Just visit my U47 info website and check the U47 circuit diagram there for the VF14 pin layout. (pin 3 for case connection is the pin "s" (s for shield), pins 5 and 6 are indicated as f1 and f2 (f for filament) in the Neumann schematics)
If these simple tests do not appear right, do not plug the tube into your U47! (if you are unsure contact me). In case the above tests are looking bad, contact the seller immediately and confront him with the facts. Remember that since you have not plugged in the tube, he can't come up with the story that your mic or power supply has killed the tube!
You can certainly send me the tube for a test, however if the tube you sent will turn out to be one of these fake VF14, there is nothing I can do (apart from writing you a report/assessment).
Unfortunately there is no way to transform an EF11 or similar with a "VF14" imprint in a nice VF14 box into a real VF14...
Here are some details of the fake VF14 imprint (left the "fake" VF14, right a real VF14):
