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Bruce Schultz
31-Jul-2016, 13:30
One of my old gra lab timers keeps going after the sweep hand gets to zero. Is the repair easy for that problem?

Randy Moe
31-Jul-2016, 16:11
I had an old one that would not start.

I unplugged it, opened it up and poked everything. "Everything" looked fine. Like new.

I fixed nothing.

I put it back together and it has now worked 4 more years.

That said, I also have a new style all plastic one I bought new 20 years ago. It appears to be safer in a wet room. It has water protected switches. I use it most, but need 2.

Regardless of machine or any electrical object, I always turn it on with one hand behind my back, so I don't touch a metal sink, plumbing nor anything that could be a ground. Enlargers also.

I have been shocked when I was a boy experimenting with tube radios and TV's. My dachshund would chew cords, get a shock and bark at them. She loved doing that...

oldlincoln
31-Jul-2016, 16:31
A limit switch has moved in all likelihood. Don't forget to unplug it before opening. If the faceplates are held by screws it'll be easy to get into. If it has pop rivets you'll have to drill them out and replace them with #6 or #8 sheetmetal screws.
At my age relying on memory becomes rather more dodgy, but I think you only need to open the rear cover plate to get to the works and the switches are held in position by socket set screws (a.k.a. Allen head).
Good luck

mdarnton
31-Jul-2016, 17:44
Are you sure it won't stop, ever? It's easy for a loose minute hand to wander off, and then real zero ends up being 56 minutes or something, some time that you never use. You won't discover that until you set it to zero and let it count backwards for an hour and discover it stopped at 56 or 43 or something, because there's no stop at zero to tell you when you're there--the only way to know for sure what it thinks is zero is when it stops there on its own.