All our tubes are tested and guaranteed by us; we only test tubes on one of our quality calibrated mutual conductance testers, NEVER on an emissions tester.  The tester we use is a computerized cardmatic tester from Tubesontheweb dot com; the specific model is a Western Electric KS-15874-L2 which was made for Western Electric by Hickok.  Our backup tester which we use occasionally is a military TV-10D/U.  For specialized tests, we employ one of our VTV Dual Triode Characterizers (for preamp tubes) as well as a Maxi-Matcher (for power tube matching).  Tubes are guaranteed for 90 days, refund or replacement our choice.  Vintage Electron Inc. possesses the largest inventory of NOS Dynaco parts available anywhere in the world, having purchased both the remaining warehouse inventory of the old Sound Values/Stereo Cost Cutters Inc. (SV/SCC) operation as well as the remaining inventory of the old Dynaco National Service Center.  SV/SCC was the company that purchased nearly 250,000 pounds of Dynaco parts when Dynaco closed it’s doors back in 1979; they also purchased the existing Hafler inventory from the Rockford Fosgate Corporation back in the early 1990‘s.  Quantities of some parts (both Dynaco and Hafler) are very limited as can be expected.  Vintage Electron Inc. has no affiliation with the old SV/SCC company and we do not provide repair services at this time for any of the Sound Valves brand products.  Please visit our store and search under the Dynaco section for additional Dynaco items, search under the Hafler section for Hafler items, and search under the Sound Valves section for Sound Valves items.