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Tube Testing
How we test our tubes:
Before we sell or ship each tube is fully tested on our calibrated Hickok 539C tube tester.
Every tube, whether used or NOS (New Old Stock) is tested for shorts using our Hickok 539C Ohm-meter. We don’t neon test for shorts, as it isn't a sensitive enough test. We test the tubes for shorts hot and cold to 50MOhms.
We test all tubes for mutual conductance (sometimes referred to as trans-conductance) including each section, if applicable. Hickok 539C provides a minimum acceptable mutual conductance. We will not sell tubes that meet these minimums. Most tube manufacturers provide new tube mutual conductance range(s), and we test to these range(s).
If a used or NOS tube is on the lower end of the manufacturer's range we discount the price of the tube. We try to post manufacturers' mutual conductance range(s), and the Hickok minimum values for each tube we sell, so you can make an informed decision on your purchase.
We also life test every tube. This is a test where the filament voltage is reduced by 10%, which gives an indication of the future performance of the tube. We discard any used or NOS tube that does not meet the life test.
If any test results in failure for shorts, leaks or open filaments, we discard the tube, and will never list it.
Tube and box condition:
If we have doubts about the NOS status of a tube, we sell it as used, even if the tube has a good box. Remember, all of our tubes whether used or NOS are fully tested before we sell them.
We sometimes have tubes with loose bases. Our policy is to note this in the description of the tube, and discount the price accordingly. We don’t sell any tube with a significantly loose base, unless the tube is exceptionally rare. If this is the case, it will be well noted in the tube's description. You can be sure that when we say a base is loose, it is only slightly loose and can be used as-is.
Some of our tubes come with original boxes. If the used, NOS or NIB tube description does not indicate the tube is packed in its original box, it will be packed in a new, standard white box. If a used, NOS or NIB tube has an original box, we will also describe its condition, as often the box is just as interesting and collectable as the tube itself. If any used, NOS or NIB tube has an original box in poor condition and we pack it in a new standard white box, we will give you the original box as well. Since we open all boxes to test them, sometimes the box flaps or tabs are damaged and we will note this in the description of the tube.
Visit us at our workshop and warehouse 941 Santa Fe Drive in the Art District in Denver, Colorado.
We are located on the west side of the street, in the stucco building at the rear of the parking lot, access from Santa Fe Drive, through the large gates. Offstreet parking available.
Our current hours are Tuesday through Friday, 10 am to 6 pm, Saturday 10 am to 4 pm.. We are available other times by appointment. Call us at (303) 534-5170 or Peter's mobile (303) 862-2763.
Or email us at info@vacuumtubesupplies.com
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