I have had numerous Ballys with the HV in this condition. An unfortunate design choice by Bally to let the Displays go to full 240v and really cook the displays instead of having them go off, but I guess this design keep the game earning money.

I always just buy one of the "high voltage rebuild kits" that are available from many vendors. Just replace all of the parts with the parts in the kit. No need to think and try and figure out which part(s) are bad. Just replace them all and be done with it. These rebuild kits have always fixed the problem for me.

BTW, I turn my high voltage down to 160-170v (just turn the pot down all the way or until just before the displays go out). You won't notice a difference and I have been told it will dramatically increase the life of all parts.