Help removing Ampeg V4 death cap?

[EWaffle]

I have a 1974 V4 head that shocks me every now and then, usually when touching my guitar strings and touching another person who is touching their strings,...

[sig]

I brought this MASCO MAP 15 back to life with a cap job and new tubes. Yesterday, I replaced the original 2 prong power cord with a gounded 3 prong. It didn't...