2 Vintage Used 1940s WWII SYLVANIA JAN-CHS-6SN7GT VT-231 Tubes, They Both Tested Fantastic On A Jackson 648 Tester. No Leakage Or Shorts. Closely Balanced Tubes, Might Be A Matched Set. They Have Matching Code Dates. No Boxes As They Were In Terrible Shape. Great Testing Tubes. Legandary 2 Hole BAD BOY Tubes. The Tube Tester Results Are Very Accurate, Test The Same On Both Plates On Both Tubes.

** PERFECT BALANCED PLATES!! *** US NAVY SYLVANIA JAN CHS 6SN7W / VT-231 TALL BottleChrome DOME Top TUBE 1944/1945 WW2 PEARL HARBORtest very well Audio Tube AMP Amplifier TV-7/u Tested STRONG!! Priced to sell! Good MEASUREMENTS across all 6 Tv-7/u Tube testers!!!! Tested to be in guaranteed working conditionI tested these on a High Quality Professonal Military Calibrated Hickok TV-7/U Testers: TUBEs TEST RESULTs: TUBE: 92/92 - {Minimum Rating of 50/50 for TV-7 Testers are equal to 65% of average new ratings.} *** I WILL COMBINE SHIPPING COSTs ON MY ITEMS FOR SALE - SAVE BIG $$ !!! If you have Questions or Comments contact me on eBay Check out the photos! TESTED WITH a (TV-7/U) FOR GAS, SHORTS, AND MUTUAL CONDUCTANCE AND ARE MOSTLY STRONG TUBES! I Combine ShippingBefore You Pay. I accept PayPal and Postal M O.Please see click to enlarge photos for condition and quality.Check out My Other Items For Sale!WILL BE SHIPPED OUT FAST! Before bidding please read my shipping and return policy. I WILL COMBINE SHIPPING COST ON MY ITEMS!!! NOTE: International buyers - THE BUYER IS RESPONSIBLE FOR SHIPPING FEES. INTERNATIONAL BIDS WELCOME. I WONT CHANGE DECLARED VALUE ON CUSTOM FORMS AND INTERNATIONAL BUYERS ARE RESPONSIBLE FOR ALL TAXES, CUSTOM FEES, and additional shipping fees. ANY RETURN WILL BE ACCEPTED BUT BUYER WILL PAY SHIPPING FEES AND I WILL NOT REFUND ANY SHIPPING FEES.*TESTED ON Calibrated HICKOK TV-7 B/U*{Minimum Ratings for TV-7 Testers are equal to 65% of average new ratings.}ALL tubes will be ran through a Daniel Nelson calibrated HICKOK TV-7 B/U for a full mutual conductance test. This is a world class tester that is calibrated by the Hickok doctor. Its test results are dead on and you can buy with confidence. If you want to know what the exact Gm rating of the tube is please message me. My Return Policy: Will not accept returns for reasons such as ordered the wrong item, change mind, not what I thought It was, wrong color ordered, item ordered.

2 x JAN-CHS-6SN7gt Sylvania Tubes Made in USA 3-hole Black Plates VT-231 = Military Specifications Matching production codes E2M = 1952 Emporium PA. plant Matching Warranty codes - 238 Tested on enhanced Triplet E3444 Laboratory Tester by Paul Hart of Ga. Results = 2450/2550 micromhos @ 7.7/7.9 mA 2450/2500 micromhos @ 8.2/8.2 mA Bogey(100% or New) = 2600/2600 micromhos @ 9.0/9.0 mA +/- 10% The measurements in this listing were taken on a Triplett 3444 modified to test the tube as an amplifier in accordance with RMA/EIA specifications, utilized by all US and most foreign tube manufacturers. This tester applies test conditions for this tube as shown below (including the precise filament voltage) and then measures transconductance (gm) in accordance with the engineering definition of gm. Tubes may also be operated under the test conditions for extended periods to be sure that it is stable. A tube must be tested in this manner to compare its test results with the manufacturer’s original intent or with other tubes of the same type. Most tube testers do not apply the test conditions required or conduct a valid gm test. For more details on the test and our test equipment, please contact us.The test conditions for this listing are__250_V plate, __250_V screen, ___-8___Vbias or Cathode resistance What were your tubes tested at?I do combine S&H

2 x JAN-CHS-6SN7gt Sylvania Tubes Made in USA 2-hole Black Plates VT-231 = Military Specifications US Navy Tested on enhanced Triplet E3444 Laboratory Tester by Paul Hart of Ga. Results = 2810/2760 micromhos @ 9.7/9.2 mA 2690/2670 micromhos @ 8.5/9.2 mA - missing guide pin, but marked Bogey(100% or New) = 2600/2600 micromhos @ 9.0/9.0 mA +/- 10% The measurements in this listing were taken on a Triplett 3444 modified to test the tube as an amplifier in accordance with RMA/EIA specifications, utilized by all US and most foreign tube manufacturers. This tester applies test conditions for this tube as shown below (including the precise filament voltage) and then measures transconductance (gm) in accordance with the engineering definition of gm. Tubes may also be operated under the test conditions for extended periods to be sure that it is stable. A tube must be tested in this manner to compare its test results with the manufacturer’s original intent or with other tubes of the same type. Most tube testers do not apply the test conditions required or conduct a valid gm test. For more details on the test and our test equipment, please contact us.The test conditions for this listing are__250_V plate, __250_V screen, ___-8___Vbias or Cathode resistance What were your tubes tested at?I do combine S&H

2 x JAN-CHS-6SN7gt Sylvania Tubes Made in USA 2-hole Black Plates VT-231 = Military Specifications Tested on enhanced Triplet E3444 Laboratory Tester by Paul Hart of Ga. Results = 2430/2580 micromhos @ 7.5/8.1 mA 2450/2500 micromhos @ 6.7/8.2 mA Bogey(100% or New) = 2600/2600 micromhos @ 9.0/9.0 mA +/- 10% The measurements in this listing were taken on a Triplett 3444 modified to test the tube as an amplifier in accordance with RMA/EIA specifications, utilized by all US and most foreign tube manufacturers. This tester applies test conditions for this tube as shown below (including the precise filament voltage) and then measures transconductance (gm) in accordance with the engineering definition of gm. Tubes may also be operated under the test conditions for extended periods to be sure that it is stable. A tube must be tested in this manner to compare its test results with the manufacturer’s original intent or with other tubes of the same type. Most tube testers do not apply the test conditions required or conduct a valid gm test. For more details on the test and our test equipment, please contact us.The test conditions for this listing are__250_V plate, __250_V screen, ___-8___Vbias or Cathode resistance What were your tubes tested at?I do combine S&H

PERFECT NOS MATCHED PAIR 6SN7GT / VT-231 HIGH GRADE SYLVANIA VINTAGE TUBES . BOTH TUBES 100% GUARANTEED NEW OLD STOCK PERFECT IN EVERY WAY YOU GTE THE 2 TUBES ONE ORIGINAL BOX & ONE GENERIC BOX FOR THE PRICE BOTH TUBES MADE THE EXACT SAME DESIGN AND PLATE STRUCTURE . MADE WITH BLACK SQUARE PLATES . THESE 2 HOLE BADBOY STLE PLATE TUBES WILL SOUND FANTASTIC RARE TO FIND A PERFECT MATCHED PAIR IN NEW CONDITION FROM THIS ERA MADE IN THE EARLY 1950S IN THE USA THEY HAVE FOIL GETTERS

1960s Matched Pair JAN CHS 6SN7WGTA Sylvania Tube Vintage USA 6SN7GT. In great shape. Tested. Low noise and microphonics.

** PERFECT BALANCED PLATES!! *** US NAVY SYLVANIA JAN CHS 6SN7W / VT-231 TALL BottleChrome DOME Top TUBE 1944/1945 WW2 PEARL HARBORtest very well Audio Tube AMP Amplifier TV-7/u Tested STRONG!! Priced to sell! Good MEASUREMENTS across all 6 Tv-7/u Tube testers!!!! Tested to be in guaranteed working conditionI tested these on a High Quality Professonal Military Calibrated Hickok TV-7/U Testers: TUBEs TEST RESULTs: TUBE: 92/92 - {Minimum Rating of 50/50 for TV-7 Testers are equal to 65% of average new ratings.} *** I WILL COMBINE SHIPPING COSTs ON MY ITEMS FOR SALE - SAVE BIG $$ !!! If you have Questions or Comments contact me on eBay Check out the photos! TESTED WITH a (TV-7/U) FOR GAS, SHORTS, AND MUTUAL CONDUCTANCE AND ARE MOSTLY STRONG TUBES! I Combine ShippingBefore You Pay. I accept PayPal and Postal M O.Please see click to enlarge photos for condition and quality.Check out My Other Items For Sale!WILL BE SHIPPED OUT FAST! Before bidding please read my shipping and return policy. I WILL COMBINE SHIPPING COST ON MY ITEMS!!! NOTE: International buyers - THE BUYER IS RESPONSIBLE FOR SHIPPING FEES. INTERNATIONAL BIDS WELCOME. I WONT CHANGE DECLARED VALUE ON CUSTOM FORMS AND INTERNATIONAL BUYERS ARE RESPONSIBLE FOR ALL TAXES, CUSTOM FEES, and additional shipping fees. ANY RETURN WILL BE ACCEPTED BUT BUYER WILL PAY SHIPPING FEES AND I WILL NOT REFUND ANY SHIPPING FEES.*TESTED ON Calibrated HICKOK TV-7 B/U*{Minimum Ratings for TV-7 Testers are equal to 65% of average new ratings.}ALL tubes will be ran through a Daniel Nelson calibrated HICKOK TV-7 B/U for a full mutual conductance test. This is a world class tester that is calibrated by the Hickok doctor. Its test results are dead on and you can buy with confidence. If you want to know what the exact Gm rating of the tube is please message me. My Return Policy: Will not accept returns for reasons such as ordered the wrong item, change mind, not what I thought It was, wrong color ordered, item ordered.

WELCOME TO OUR AUCTION============================== JAN CHS 6SN7 WGT SYLVANIA RADIO TUBE CHROME TOP - BROWN BASE 547 - TV-7 D/U TEST RESULTS - 70/66 AND MINIMUM IS 50/50 ===================================================================================== WE WILL BE LISTING LOTS OF NEW ITEMS WEEKLY DO CHECK BACK. *International Buyers*PLEASE ASK FOR SHIPPING QUOTE BEFORE YOU PLACE A BID. ----------------------------------------------------------------------------------------------- *U.S. BUYERS - $6.00 - 1ST CLASS MAIL

Sylvania JAN-CHS-6SN7W tube. U.S Navy Chrome Dome Amplitrex Tested, Balanced 92% gm Parallel T Plates. Tube was checked for noise and microphonics One of the well known attributes of the Amplitrex is the sensitivity it has for gas testing. It is likely other tube testers will show no gas at all for these tubes. Amplitrex AT1000 results. New tube spec mhos is 2600/2600 with plate voltage at 250 VDC.TubeEmissions %GM % mhosH-K uAGas mA6SN7W106/10092/922400/24000/0.8/.8 Acceptable practice is to have the gas below 1ma. So it is within the good range. Cleaning the tube is being left to the buyer since often cleaning the tube also removes labeling.Results are written on the tube. These can be easily removed with a moist paper towel. Domestic purchases can be combined to reduce shipping costs. International shipping is through the ebay Global Shipping Program. This program may not combine shipping. Contact eBay to find out. Items usually ship the day after payment is received.

Accepted, along with all eBay approved payment methods. - Payment required within (3) days of purchase or auction close.ReturnsNo return offered for this listing. Shipping Item usually ships within (3) business days of cleared payment. Note: This item may be eligible for international shipping either directly or through the eBay Global Shipping Program. If you are a buyer from outside of the US please contact me for additional details.Sales TaxeBay now automatically collects sales tax for all shipped transactions. If you are picking up your purchase from us in NYC, 8.875% local sales tax will be charged

Sylvania JAN CHS 6SN7WGT, USED TESTED 6SN7 MILITARY TUBE. When the difference of cost is a couple of dollars I use priority mail

Test Good

6SN7WGT JAN CHS Tube Sylvania Brown Base Chrome Top TESTED. Tested on Sencore MU140

** PERFECT BALANCED PLATES!! *** US NAVY SYLVANIA JAN CHS 6SN7W / VT-231 TALL BottleChrome DOME Top TUBE 1944/1945 WW2 PEARL HARBORtest very well Audio Tube AMP Amplifier TV-7/u Tested STRONG!! Priced to sell! Good MEASUREMENTS across all 6 Tv-7/u Tube testers!!!! Tested to be in guaranteed working conditionI tested these on a High Quality Professonal Military Calibrated Hickok TV-7/U Testers: TUBEs TEST RESULTs: TUBE: 92/92 - {Minimum Rating of 50/50 for TV-7 Testers are equal to 65% of average new ratings.} *** I WILL COMBINE SHIPPING COSTs ON MY ITEMS FOR SALE - SAVE BIG $$ !!! If you have Questions or Comments contact me on eBay Check out the photos! TESTED WITH a (TV-7/U) FOR GAS, SHORTS, AND MUTUAL CONDUCTANCE AND ARE MOSTLY STRONG TUBES! I Combine ShippingBefore You Pay. I accept PayPal and Postal M O.Please see click to enlarge photos for condition and quality.Check out My Other Items For Sale!WILL BE SHIPPED OUT FAST! Before bidding please read my shipping and return policy. I WILL COMBINE SHIPPING COST ON MY ITEMS!!! NOTE: International buyers - THE BUYER IS RESPONSIBLE FOR SHIPPING FEES. INTERNATIONAL BIDS WELCOME. I WONT CHANGE DECLARED VALUE ON CUSTOM FORMS AND INTERNATIONAL BUYERS ARE RESPONSIBLE FOR ALL TAXES, CUSTOM FEES, and additional shipping fees. ANY RETURN WILL BE ACCEPTED BUT BUYER WILL PAY SHIPPING FEES AND I WILL NOT REFUND ANY SHIPPING FEES.*TESTED ON Calibrated HICKOK TV-7 B/U*{Minimum Ratings for TV-7 Testers are equal to 65% of average new ratings.}ALL tubes will be ran through a Daniel Nelson calibrated HICKOK TV-7 B/U for a full mutual conductance test. This is a world class tester that is calibrated by the Hickok doctor. Its test results are dead on and you can buy with confidence. If you want to know what the exact Gm rating of the tube is please message me. My Return Policy: Will not accept returns for reasons such as ordered the wrong item, change mind, not what I thought It was, wrong color ordered, item ordered.

** PERFECT BALANCED PLATES!! *** US NAVY SYLVANIA JAN CHS 6SN7W / VT-231 TALL BottleChrome DOME Top TUBE 1944/1945 WW2 PEARL HARBORtest very well Audio Tube AMP Amplifier TV-7/u Tested STRONG!! Priced to sell! Good MEASUREMENTS across all 6 Tv-7/u Tube testers!!!! Tested to be in guaranteed working conditionI tested these on a High Quality Professonal Military Calibrated Hickok TV-7/U Testers: TUBEs TEST RESULTs: TUBE: 92/92 - {Minimum Rating of 50/50 for TV-7 Testers are equal to 65% of average new ratings.} *** I WILL COMBINE SHIPPING COSTs ON MY ITEMS FOR SALE - SAVE BIG $$ !!! If you have Questions or Comments contact me on eBay Check out the photos! TESTED WITH a (TV-7/U) FOR GAS, SHORTS, AND MUTUAL CONDUCTANCE AND ARE MOSTLY STRONG TUBES! I Combine ShippingBefore You Pay. I accept PayPal and Postal M O.Please see click to enlarge photos for condition and quality.Check out My Other Items For Sale!WILL BE SHIPPED OUT FAST! Before bidding please read my shipping and return policy. I WILL COMBINE SHIPPING COST ON MY ITEMS!!! NOTE: International buyers - THE BUYER IS RESPONSIBLE FOR SHIPPING FEES. INTERNATIONAL BIDS WELCOME. I WONT CHANGE DECLARED VALUE ON CUSTOM FORMS AND INTERNATIONAL BUYERS ARE RESPONSIBLE FOR ALL TAXES, CUSTOM FEES, and additional shipping fees. ANY RETURN WILL BE ACCEPTED BUT BUYER WILL PAY SHIPPING FEES AND I WILL NOT REFUND ANY SHIPPING FEES.*TESTED ON Calibrated HICKOK TV-7 B/U*{Minimum Ratings for TV-7 Testers are equal to 65% of average new ratings.}ALL tubes will be ran through a Daniel Nelson calibrated HICKOK TV-7 B/U for a full mutual conductance test. This is a world class tester that is calibrated by the Hickok doctor. Its test results are dead on and you can buy with confidence. If you want to know what the exact Gm rating of the tube is please message me. My Return Policy: Will not accept returns for reasons such as ordered the wrong item, change mind, not what I thought It was, wrong color ordered, item ordered.

Jan-CHS 6sn7 Wgt Sylvania (4 pieces) Tv7 Test Very Strong Sold as is/No return shipping US Only

Two Sylvania JAN-CHS-6SN7W tubes One is marked 6SN7A on top, one is marked 6SN7W on top. Both are marked 6SN7W on the side. Tested good with TV-7 tester. Results 100, 105 and 92, 89 (50 min). Washington State residents must pay sale tax.

Vintage Sylvania Jan-chs-6sn7w Tub.

Sylvania JAN-CHS-6SN7W tube. U.S Navy Chrome Dome Amplitrex Tested, Balanced 92% gm Parallel T Plates. Tube was checked for noise and microphonics One of the well known attributes of the Amplitrex is the sensitivity it has for gas testing. It is likely other tube testers will show no gas at all for these tubes. Amplitrex AT1000 results. New tube spec mhos is 2600/2600 with plate voltage at 250 VDC.TubeEmissions %GM % mhosH-K uAGas mA6SN7W106/10092/922400/24000/0.8/.8 Acceptable practice is to have the gas below 1ma. So it is within the good range. Cleaning the tube is being left to the buyer since often cleaning the tube also removes labeling.Results are written on the tube. These can be easily removed with a moist paper towel. Domestic purchases can be combined to reduce shipping costs. International shipping is through the ebay Global Shipping Program. This program may not combine shipping. Contact eBay to find out. Items usually ship the day after payment is received.

** PERFECT BALANCED PLATES!! *** US NAVY SYLVANIA JAN CHS 6SN7W / VT-231 TALL BottleChrome DOME Top TUBE 1944/1945 WW2 PEARL HARBORtest very well Audio Tube AMP Amplifier TV-7/u Tested STRONG!! Priced to sell! Good MEASUREMENTS across all 6 Tv-7/u Tube testers!!!! Tested to be in guaranteed working conditionI tested these on a High Quality Professonal Military Calibrated Hickok TV-7/U Testers: TUBEs TEST RESULTs: TUBE: 92/92 - {Minimum Rating of 50/50 for TV-7 Testers are equal to 65% of average new ratings.} *** I WILL COMBINE SHIPPING COSTs ON MY ITEMS FOR SALE - SAVE BIG $$ !!! If you have Questions or Comments contact me on eBay Check out the photos! TESTED WITH a (TV-7/U) FOR GAS, SHORTS, AND MUTUAL CONDUCTANCE AND ARE MOSTLY STRONG TUBES! I Combine ShippingBefore You Pay. I accept PayPal and Postal M O.Please see click to enlarge photos for condition and quality.Check out My Other Items For Sale!WILL BE SHIPPED OUT FAST! Before bidding please read my shipping and return policy. I WILL COMBINE SHIPPING COST ON MY ITEMS!!! NOTE: International buyers - THE BUYER IS RESPONSIBLE FOR SHIPPING FEES. INTERNATIONAL BIDS WELCOME. I WONT CHANGE DECLARED VALUE ON CUSTOM FORMS AND INTERNATIONAL BUYERS ARE RESPONSIBLE FOR ALL TAXES, CUSTOM FEES, and additional shipping fees. ANY RETURN WILL BE ACCEPTED BUT BUYER WILL PAY SHIPPING FEES AND I WILL NOT REFUND ANY SHIPPING FEES.*TESTED ON Calibrated HICKOK TV-7 B/U*{Minimum Ratings for TV-7 Testers are equal to 65% of average new ratings.}ALL tubes will be ran through a Daniel Nelson calibrated HICKOK TV-7 B/U for a full mutual conductance test. This is a world class tester that is calibrated by the Hickok doctor. Its test results are dead on and you can buy with confidence. If you want to know what the exact Gm rating of the tube is please message me. My Return Policy: Will not accept returns for reasons such as ordered the wrong item, change mind, not what I thought It was, wrong color ordered, item ordered.

Je vous propose ces quatre SYLVANIA VT-231 JAN-CHS-6SN7GT Fabriqués aux U.S.A. en 1945 pour lU.S. ARMY-NAVY Les tubes sont 100% inutilisésExpédiés dans une boite brune neuveTestés sans ronflement ni microphonie sur un préampli Mexing MC7R-II et sur un intégré 2E22 BEZ T3A-42 sur des JBL 2445/E140/4560 Mesurés sur lampemètre électronique Duovac :Anode : 250VGrille : - 8V 9mA = 100% Tube 1 : 9,9mA et 8,5mA Tube 2 : 9mA et 8,1mA Tube 3 : 8,5mA et 9,7mA Tube 4 : 8,3mA et 9,2mA SYLVANIA VT-231 JAN-CHS-6SN7GT Made in U.S.A. for U.S. ARMY - NAVY Same date code C5 : 1945 Same structure inside and out Firm basesSupplied in new brown box They are tested on a Duovac digital tube tester Anode : 250V Grid : - 8V 9mA = 100%Tube 1 : 9,9mA and 8,5mA Tube 2 : 9mA and 8,1mA Tube 3 : 8,5mA and 9,7mA Tube 4 : 8,3mA and 9,2mAThoses valves has also been tested on a Mexing MC7R-II preamp and a 2E22 BEZ T3A-42 amplifier on JBL 2445/E140/4560 with no hum or microphonics that can be heard NOS, the tubes are 100% unused EXPEDITION FRANCE : 11€ en Colissimo contre signature SHIPPING EUROPEAN UNION : 15€ Colissimo tracked and signed

Sylvania JAN-CHS-6SN7W tube. U.S Navy Chrome Dome Amplitrex Tested, Balanced 92% gm Parallel T Plates. Tube was checked for noise and microphonics One of the well known attributes of the Amplitrex is the sensitivity it has for gas testing. It is likely other tube testers will show no gas at all for these tubes. Amplitrex AT1000 results. New tube spec mhos is 2600/2600 with plate voltage at 250 VDC.TubeEmissions %GM % mhosH-K uAGas mA6SN7W106/10092/922400/24000/0.8/.8 Acceptable practice is to have the gas below 1ma. So it is within the good range. Cleaning the tube is being left to the buyer since often cleaning the tube also removes labeling.Results are written on the tube. These can be easily removed with a moist paper towel. Domestic purchases can be combined to reduce shipping costs. International shipping is through the ebay Global Shipping Program. This program may not combine shipping. Contact eBay to find out. Items usually ship the day after payment is received.

This new old stock-testing matched pair of Sylvania JAN-CHS-6SN7WGTA Black Three-Hole T-Plates with Silver Top vacuum tubes was tested on our recently calibrated TV-7/U. Tubes measured: Tube One: 85 / 87 (Sylvania JAN-CHS-6SN7WGTA stenciled on glass with codes 582A 312B)Tube Two: 81 / 82 (Sylvania USN JAN-CHS-6SN7WGTA stenciled on base & code 313; USN 6SN7WGTA & Sylvania logo stenciled on glass with codes 5447A 312B) Minimum is 50 (65%); 75 = 100%. TV-7/U calibrated December 2021. As a percentage, these tubes test as follows: Tube One 113% / 116%Tube Two 108% / 109%Listened to them in our Alan Eaton amplifier and they sound outstanding (see pics); are dead quiet when the amps are muted; and have excellent frequency response, sound-staging, presence and dynamics. Pair have black three-hole T-plates (true Bad Boy status), support rods and silver tops. Bases are different sizes but does not have any affect on tube performance; tube internals are exactly the same. Tight on bases with no debris or rattling sounds. Check out our eBay store for more tubes for your equipment needs. Tubes ship via United States Postal Service (USPS) First Class Mail with tracking for domestic U.S. sale; Priority is an option. International orders ship via eBay International Shipping. Package weighs eight (8) ounces. Combined shipping always welcomed.TUBES ARE GUARANTEED GOOD AND IN WORKING ORDER AT SHIPMENT. TRANSIT VIA POST CAN DAMAGE TUBES. THIS IS NO FAULT OF OURS BUT THE THIRD PARTY ENTITY THAT IS DELIVERING ITEM(S) TO YOU, I.E, USPS, UPS, FEDEX, YOUR NATIONAL CARRIER IF INTERNATIONAL, ETC. PLEASE INSURE THEM! WE CANNOT GUARANTEE FAILURES ON YOUR EQUIPMENT AFTER POWER UP AS THERE IS NO WAY TO ASCERTAIN HOW TUBES WILL INTERACT WITH YOUR ELECTRONICS; NOR IS THERE A WAY TO DETERMINE WHETHER THEY MAY HAVE FATAL FLAWS IN TUBES THEMSELVES! THESE ARE USED VACUUM TUBES AND TIME MAY HAVE TAKEN A TOLL ON THEM OVER THE MANY YEARS SINCE THEY WERE MANUFACTURED. WE CAN ONLY TEST FOR THE PARAMETERS MENTIONED ABOVE IN ONE OR MORE OF THE FOLLOWING EQUIPMENT WE USE FOR MEASURING: TV-7/U, JACKSON 648 & MAXI MATCHER 2.