A short note:
I have been in photo for nearly 60 years. I have owned a camera store for 34 years and worked photo retail on and off since 1968. I have a reasonable background in electronics and I won't even crack the case on a camera, and especially on something like Pentax 6x7.
I don't have ready access to parts, manuals or enough knowledge to fix it. So, 'grab a multimeter...' may not be a suitable response to the original poster's problem.
Not knowing what you are about can cause more damage than may originally exist or a spring 'explodes' and you lose parts or cannot figure out how to put 'it' back, whatever 'it' may be.
I am not being critical here, just practical, just like fixing my own car, ain't gonna happen.
These days, things can be so complicated (even the very old stuff) that it is a nightmare.
I once sent a Leica M3 (that's old) to a repair facility for service, and learned even trained and skilled repair techs can do some things and not others. German cars (3 Audis and 5 or 6 VW'S) are best handled by people who know what they are about, and thank goodness there are people with more skill than I have. And having just been through a triple bypass, that simply reinforces my thankfulness that somebody knows what they are doing and I hope finds great pleasure in their skills and abilities.