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.. Is it possible I need to modify the resistor inline with my POTS in my Mark 3s? i have never had to do this before but is that something that sometimes need to be done for certain brands of tubes? I see nothing technically wrong on the tube tester with them. Note: On both my MK3s Ihave 1K resistor in thebias chain instead of the 4.7K that was recommended for the removed selenium mod. I never changed them because I could achieve the 1.56V fine with room to spare. Could it be that I need to change it to the 4.7K? If so why for these tubes only? i have used several brands with no issue before these PSVANE tubes.
Last edited by bubbasweet on Fri Jul 22, 2022 1:08 am; edited 2 times in total (Reason for editing : Add to post)