Jet 1642 Troubleshooting

Re: Jet 1642 Troubleshooting

Doc Green

Assuming the pickup/display unit is similar to what's on a PM3520B, it is likely that the pickup disk mounted on the spindle has shifted to the side so that the pickup diode no longer sees the disk. If this is the case, moving the disk back to its original position should restore normal operation.

Remove four screws (at the corners) and pull the display unit out of the headstock case until you can see inside. You should see the disk, which is secured to the spindle with a setscrew (or maybe two).

The pickup diode mounted on the display unit should line up with the disk. Here's a photo of the diode on a PM:

This shows the relationship between the pickup and the disk on a PM:

Good luck! ~Doc

Re: Jet 1642 Troubleshooting

John K Jordan

If the lathe still works and if for some reason you can't get the speed display working, an option is to use it without the speed display. Many turners, John Lucas for example, use the PM 3520 with no speed control. In fact, I seldom look at the numbers on my PM3520b or my Jet 1642 - I just turn the speed to what feels right.

If you want some idea of the speed, you can do what I did with my variable speed milling machine with no tach display - I measured the speed with a cheep optical tachometer (from Amazon, https://www.amazon.com/gp/product/B004Q8L894) and made marks on the dial for 250, 500, 1000, etc rpm.

Of course, if it was mine, I'd want to fix it too, just because. Most that I've heard of with this problem were due to exactly the reason that the good Doc mentioned. Also, check the connector and wire to the sensor.

JKJ

Re: Jet 1642 Troubleshooting

jake niedling

I have never had an RPM readout, so not having it doesn't seem like much of an issue. My PM 3520A was not equipped with one. I adjust the the speed depending on all the variables that we all run into ( diameter, balance, cut, vibration, type of wood, etc.). Sounds like Doc has some good advice, as he always does. Good luck.

Re: Jet 1642 Troubleshooting

mikeee12345

If it ends up being a bad sensor you should be able to read the manufacturer and model number on the sensor and find one on Ebay or Amazon for less money. Re-aligning the target on the spindle is most likely the issue that is the problem if not it could be the sensor or a loose wire.

Re: Jet 1642 Troubleshooting

Joe Fleming

Duane, I've been turning for 20 years and have never had a speed read-out. I just use common sense. When the lathe tries to walk out of the shop, the speed is too fast. Joe

Re: Jet 1642 Troubleshooting

Duane Wiedman

Thanks guys for all the opinions. The unit works on the same theory as the 3520 but they do it differently. The main shaft looks like they have bolt heads tapped and threaded into the main shaft. The sensor doesn't look like it quite lines up with the bolt heads but nothing appears to be loose. The bracket that holds the sensor is quite stiff and not not easily moved. I also can't find anything loose on the shaft. The wires also look good. A mechanic I ain't.

I'm going to use the lathe without the read-out for the time being. I agree with the fact there are a lot of variables in what we turn. I appreciate all the input but because I'm cheap I'm going to limp along until it drives me bonkers.