Canon 7 shutter leaks

[e_asphyx]

I seems like the shutter's curtain sometimes doesn't fully close and the shutter leaks some light in uncocked position. My guess is the spring of the following (closest to the lens) curtain is a bit weak. I'm afraid that I may affect the shutter speed messing with those springs. I can try to measure it though using a photo diode and an oscilloscope. I'd appreciate any advice.
Shutter photo and sample image: https://imgur.com/a/vPAiZJN

 

[Chriscrawfordphoto]

Increasing the spring tension will affect shutter speeds and evenness of the exposure. It'll also shorten the camera's lifespan. The problem you have is probably caused by dried lubricants or dirt in the mechanism. It needs to be disassembled and cleaned, relubricated, and adjusted by a professional technician.

 

[Moto-Uno]

^ +1 , it looks the exact same as my Pentacon Six when used at 1/125 and then slowly progressed into other speeds . De-greasing the mechanism was magic . Peter