RPM readout on JET lathe stopped working

[Bill Bell]

The digital RPM readout on my JET 1640 lathe has stopped working. I've pretty much gotten used to judging the speed by feel but would still like to know how fast I'm turning. The manual rather unhelpfully says to "position sensor so that it reads the bolts." I'm not really sure what this means - when I open up the headstock I see the sensor underneath what is evidently the housing for the spindle (see photo) but it's not clear what the "bolts" refer to unless it's the two set screw in the housing; nor is it clear (in what direction) I would reposition the sensor. Suggestions, anyone?

[Jim Morgan]

If the display is completely dark, you probably need a new LED readout. If the readout is illuminated but stuck at 0, the problem is either in the sensor or in one of the wiring connections to the sensor.

[Earl McLain]

If you don't find a cheap/simple enough solution--i use this for my Robust Sweet 16 (newer Sweet 16's have one built-in). It matches the read-out on my little Rikon, so it's close enough. Amazon.com: Digital Laser Photo Tachometer Gauce for car,Wheels,engines,Non Contact Tach RPM meter,2.5RPM-99,999RPM Motor Speed Meter Gauge Tool includes Reflective Tapes : Industrial & Scientific

[Bill Howatt]

It likely is sensing the dark setscrews either optically or magnetically. If so, the sensor should be close to and aligned with them.
I don't have a RPM readout on my General and I don't really need or want it. But, I'm not you! However, you could get the tach like Earl mentioned and calibrate the knob on your control panel since this is not a high-precision requirement for operation. Do both ranges, of course.

[Chris Parks]

If it is an optical sensor try cleaning the lens.

[Curt Harms]

If you don't find a cheap/simple enough solution--i use this for my Robust Sweet 16 (newer Sweet 16's have one built-in). It matches the read-out on my little Rikon, so it's close enough. Amazon.com: Digital Laser Photo Tachometer Gauce for car,Wheels,engines,Non Contact Tach RPM meter,2.5RPM-99,999RPM Motor Speed Meter Gauge Tool includes Reflective Tapes : Industrial & Scientific

That seems like a practical solution if the existing hardware can't be resurrected. I wouldn't think that precise speeds are critical.

[Earl McLain]

That seems like a practical solution if the existing hardware can't be resurrected. I wouldn't think that precise speeds are critical.

I bought a used Robust Sweet 16 a few years ago that had no speed read-out (newer ones do). E-mailed Brent @ Robust to ask a few questions and enquired as to whether i could retro-fit one. Brent suggested the one i linked to instead of spending $400 +/- on an upgrade. Now i only use it to reference speed to describe turning problems--otherwise i'm mostly by vibration feel.

[Curt Harms]

I've read that you may not even need the reflective tape for those. Often a little strip of white electrical tape or a chalk mark on dark metal will do the trick.

[Bill Howatt]

I've read that you may not even need the reflective tape for those. Often a little strip of white electrical tape or a chalk mark on dark metal will do the trick.

Some even work in the opposite mode too, dark tape/mark on a "bright" background.