by arremondo Fri Apr 15, 2022 12:41 pm
So I have been using Gold Lion KT88s in my VTA board ST70 with a new PS60 that has a higher power rating. I have done the yellow sheet diode fix on the rectifier socket and the Triode / Ultralinear switches. I just leave it in Ultralinear most of the time. Anyway, with the Russian tubes not being shipped with the war going on I decided to order some PSVane KT88s from China. Keep in mind that I have been using the Gold Lions for almost a year without problems. So I put in the PSVane KT88s after I had dialed down the bias on all 4 pots. While I was setting the bias, I got "lightning in a bottle" on my 5AR4 then blew the fuse. It didn't even run long enough for me to dial up the voltage to .5. So I thought that maybe the settings for the bias were still too high so I dialed them way back, replaced the 5AR4 and tried again. I got the same thing. So after blowing my last 5AR4 (a Gold Lion no less) and another fuse, I put in my solid state rectifier and tried again. While it ran for about a minute, it then blew a fuse. So, I replaced the fuse and put the Gold Lion KT88s back in and it works just fine (except for the hum I now have that I didn't have before). I checked all of the new PSVane KT88s on my Jackson 648 and they all check good and no leaks.
Anyone have any suggestions? I am out $250 for the tubes right now and had to order another $100 of 5AR4s to replenish my stock. Any experts on here with Jackson 648 experience and have any suggestions for testing? I feel like I got a bad tube as 3 of the 4 tubes shipped with bubble wrap on them inside the tube box but one didn't have the bubble wrap. I would really like some direction on how to properly check these tubes for everything on my tube tester. I don't know if I am checking the leak and life time correctly.
Also since I don't have another tube as of yet, would a solid state rectifier cause hum in the speakers? It happens on all inputs from the preamp (Phono, Receiver, CD etc). The hum coming through the speakers increases in volume with the volume control. The multi-Capacitor is around a year old and I bought it new (not NOS). There was no hum before the "lightning in a bottle" happened.
Please don't tell me I need a better tube tester. I got what I could afford at the time. I would just like some direction.
Thank you,
Mark