Heathkit TT1a Tube tester

I recently restored the unit , complete recapping, replaced all carbon comp resistors[ way out of tolerance], ,precision resistor all on the money, did not change. As a safety precaution, The 2 prong receptacle is damaged. Replaced it with a 3 prong receptacle and 3 prong power cord., grounding  unit with the green earth ground wire to chassis.  
Is changing from non polarized cord to grounded cord going to have any adverse affect on the the tester?

Thanks,

Cags