813 Tube NOS Matched Pair RCA 1000 hour Triode connected Single end amp 211 845

813 Tube NOS Matched Pair RCA 1000 hour Triode connected Single end amp 211 845 (image 1/4)
813 Tube NOS Matched Pair RCA 1000 hour Triode connected Single end amp 211 845 (image 2/4)
813 Tube NOS Matched Pair RCA 1000 hour Triode connected Single end amp 211 845 (image 3/4)
813 Tube NOS Matched Pair RCA 1000 hour Triode connected Single end amp 211 845 (image 4/4)
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This auction is for one matched pair of NOS 813 VT-144 vacuum tubes, made by RCA for the US Army or US Navy in 1944. They are marked as They come in the original boxes which are a bit funky but the tubes test like new as they should. I assembled a test jig which can be seen in the photos to power on the filaments first with 10 volts ac then the high voltage power supply was gently ramped using a variac to the test voltage of 981 volts dc. The screen grid was connected to the plate and the suppressor grid was connected to the mid point of the filament connection, please refer to the circuit diagram in the pictures. Under such conditions the tubes passed a plate current of 97.74.1ma and 98.5 ma, a difference of .76 ma!You cannot get such closely matched tubes from new production tubes. These tubes are big and feel substantial with very thick glass. They have been used to build single ended amplifiers, connected as triodes as their curves look like 211 or 845 triode curves, see links below:/813_se_triode_amps.htm/Claudio845/813amp.htmlhttp://www.n.mackie.//813main.htmhttp://sarris.info/main/heavyweight-set-ampOr they can be used for a ham radio power amplifier rig. Please see my other items for more tube auctions. I will ship by USPS Priority mail or the buyer's preferred shipping method, please contact me for details. Tubes sold as read more
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