Posted by omnibusspresss@yahoo.com (A) on July 21, 2022 at 20:58:49

Wonder what the deal is. I took a chance on a matched Quad of PsVane KT88s. I got em today new in the mail and I tested them and they tested OK on my Stark 966 Tester but when I put them in I blew a fuse on one MK3. So replace it and then got on the Bias right away and I could only achive about 1.40 finally I realized the pot was cranked all the way to one side. The other amp blew a fuse then I tried to bias that one and I could only achieve 1.30 then I realized the rectifier blew. So down a rectifier and 3 fuses I put my old tubes (Russian Mullards) back in and had to turn the pots back to half way and everything worked and biased fine after I replaced the rectifier that had blown. THE PSvane tubes seem to be drawing excessive current for some reason. There is something wrong with these tubes. I cannot achieve proper bias with them. As well I blow 1 rectifier and 3 fuses. I am NOT REAL HAPPY. My amps are working fine with my old tubes in them and bias 1.56VDC fine with pot in center like all the other Brands of tubes I have used in last 15 years. These I cannot bias and they seem like they draw HUGE CURRENT even though they seem to test fine on tube tester. Has anyone else had this problem or know what is going on? Are the tubes bad or do I need to modify the bias resistor before the Pots? Never had to do this before..