Unfortunately this is not possible and to be fair it’s not exactly standard working procedure is ittemporarily connect the boards to a live source and test? job jobbed.

Unfortunately this is not possible and to be fair it’s not exactly standard working procedure is ittemporarily connect the boards to a live source and test? job jobbed.
Unfortunately this is not possible and to be fair it’s not exactly standard working procedure is ittemporarily connect the boards to a live source and test? job jobbed.
Can you get to the live terminal by popping the fuse out and sticking a prove in to the fuse holder? And the earth via a faceplate screw? That would give you R1 R2. The resistance might be slightly higher through the screw though so you would have to compare.
EDIT: Actually, thinking about it, im not sure if the fuse holder stops you accessing the actual live part behind