Just wondering why after all these years my Tubes for Hifi ST-70 a family member (my daughter) turning off the amp. I was outside at the time so I wasn't there to see it, but when she touched the switch the amp shocked her burning her hand a bit. She is fine, but the amp definitely juiced her a bit. She did have her phone in her other hand. I didn't test the amp when I came, I simply unplugged it, but the rectifier tube didn't appear to have blown, nor was the fuse blown. I've never had the amp shock me and I have not done anything to it recently to cause any damage to it. Ideas? By the way, I've had the amp now for about 11 years.