Hello, I am hoping to find help here. Without doing any research I bought what appears to be a 397.19340 grinder via an online auction:
http://bid.auctionnation.net/cgi-bin/mnlist.cgi?anation78/48/1
When I got it the wheels spun freely but when powered on it would make a loud buzzing/humming sound and spin very very slowly (maybe 1 RPM).
I tried spinning it up with a drill then turning it on and it would instantly slow to the 1 RPM speed. I tried spinning it up both directions with the same results.
I took the cover off and wired around both the switch and start relay (this model has no capacitor). It still buzzed.
I measured the resistance between the coil leads and they all seem in order (~11 for main winding, ~3 for the starter winding, ~14 for the combined loop). I say this is about in order based on this posting by torqueman2002:
http://www.garagejournal.com/forum/showthread.php?p=5035526&highlight=resistance#post5035526
I separated the two halves to find that 3 of the fingers that connect the two halves of the case together were broken. 2 of them were inside the case still. They were all from the same connection point, the once closest to the power switch.
JZiggy seemed to have similar problems and fixed it with shims, but I am not clear exactly where they went or how they fixed the problem.
http://www.garagejournal.com/forum/showthread.php?p=5038025&highlight=assembly#post5038025
I can understand if the shaft were binding the motor could not spin. I thought he said it would spin freely before shimming, so am not sure what was re-aligned to make it go again. I am also not sure that this case can ever be re-aligned in a way that will make it work. I assume it was tipped over at some point breaking the fingers inside. Maybe it is hopelessly out of alignment in some way now.
I have tried several times to adjusting the alignment of the two halves hoping to see some signs of life. It seems like it very subtlety changes things (not spinning at all, speeding up to 1.5 RPM), but nothing that makes me think it is going to work again.
Thanks for you help. I am excited about getting this going again. I have happened upon several older USA made tools recently and am enjoying fixing them up more than using them for some reason.
I can add pictures if helpful. Thanks for the help.
Ray