If you're getting 170 mv you're basically destroying those tubes. You'll need to check the wiring around the power tubes and/or the transformer extra carefully, find what you've done wrong and fix it. Then most likely replace the power tubes. It probably needs to go to a tech for this.
i agree. sounds like something is amiss somewhere in the bias circuitry, or maybe in the power supply circuit somewhere. either way, there is way too much current goin through there. if you can, try posting some closeups of the wiring of your tube sockets, but sduck is prolly right, you may need to take it a tech