HELP with PM 3520B - RPM Meter Stopped Working

[mike ash]

For some reason my electronic RPM readout is stuck on "0". I think I read about this problem on this site but can't seem to find it when I need it. Can anyone help with a solution?

Thanks, Mike

[Ken Fitzgerald]

Mike.....I will go check mine but I believe there is a little encoder wheel and it may have loosened up.

Back in a minute.

[John Beaver]

I had the same problem once. There is a little wheel on the spindle (right behind the L.E.D. readout) that triggers the reading. Mine had slipped a little to the side and just needed a small adjustment.

[Ken Fitzgerald]

Mike.....I just looked at mine. I don't see a circular encoder as John describes. If you remove the screws for the readout, it will tilt out slightly at the top. On the shaft behind to the left is the locking collar that is engaged when you lock the shaft to remove your face plate for example. On that collar are 4 corners of a square ...and on the bottom of the tilted op display is a little black rectangle wrapped in yellow metal . I would bet the yellow metal is aluminum. I suspect the black rectangle is a proximity sensing switch and it senses the 4 corners of the iron locking collar as they spin past with the shaft rotation...it works magnetically I'd bet....Check to see if the locking collar is loose. It is keyed and has 2 set screws. Good luck!

[mike ash]

Thanks for the tips guys! Ken's fix was exactly correct. The 4 cornered collar was apparently installed at the factory too far to the right and the lobes of the collar were not alligning so that the yellow magnetic sensor would sense them as they spun by. All I had to do was to loosen the allen set screw in the collar, slide it back to the left and retighten. Presto!!! I've got a reading.

Thanks again, Mike

[Steve Schlumpf]

Glad to hear that you were able to fix the problem!! Please keep it in mind for the next person that has a similar symptom - these things do pop up from time to time.