# Motor And Rotary Drum Switch



## glassford (Feb 20, 2016)

I want to share my recent repair experience with my Jet lathe, GHB-1340, which is 20 years old. In early November, the motor suddenly would not run.  A minute ago, it worked fine; now it won't run. In my rural county I could not find an electrician who would make a housecall to repair a motor and/or control system, and I did not relish the prospect of hauling the whole lathe to Phoenix for repair. The local small tool repair shop suggested that I remove the motor (2 hp) and controls and drop it for repair. Easier said than done, without dropping it.

For several weeks I pondered how to remove the motor. Then I realized I could loosen the motor mount screws, slide a small table under it, and lift it with several layers of plywood under it, removing the weight from the mount while I removed the three mounting screws. I carefully marked the terminals in the control box and switch with the wire numbers. I thought I did. I hauled the motor, control box, and rotary drum switch to the shop on the other side of the volcano. And waited.

The repair was completed by mid-December: the repairman visits town several times per month to fix motors, etc for the local hospital and newspaper printing plant, among other clients. Distracted by StarWars premier, a leaky power steering gear, and holidays, I did not begin to reassemble the lathe until mid-January.

I connected the wires to the switch as I marked them when I removed the switch. With the operating lever in neutral position, I released the E-stop button; the spindle began turning in reverse. It wasn't a good beginning. In forward and reserve positions, the motor didn't run. I visited the guys at the tool shop: they recalled that the motor was initially wired incorrectly. I emailed photos to JetTools: they sent me a bad sketch and some pics of a newer switch. I called the tool seller in Phoenix: the tech couldn't tell from the pics, but offered to look it over if I could haul the lathe to him. And the motor repairman suggested that I try connecting the switch wires in pairs. He said  the worst that could happen is that the circuit breaker would blow.

They were all very nice, but they couldn't provide much assistance. It was frustrating for me, but I can understand that nobody wants to give wiring advice over the phone.

I am not very electrical, although I have replaced some gizmos inside my computer. One pair at a time, I connected all the combinations of pairs of wires and released the E-stop button. With wires 2 & 4 the spindle turned forward, and with wires 2 & 5 the spindle turned reverse.  2-3, 3-4, 3-5, and 4-5 did nothing. Without sparks or blown breaker!  This was progress. Now, I just needed to figure out which combination of eight terminals on the rotary drum switch were connected or disconnected in the three switch positions. I bought a lowpriced digital multimeter from the hardware and began checking terminals. After replacing a bad battery in the meter, I found unique connections in switch positions forward and reverse which connected and some combinations in neutral which did not connect. Terminals 1, 4, 5, and 8 are jumped together. I call this the quad.

 In reverse position, the quad terminal connected to terminal 2.  In forward position,  the quad and terminal 3 connected.  In neutral, the jumped terminals did not connect to either 2 or 3. I connected wires 2 and 3 to the jumped quad, wire 4 to terminal 3, and wire 5 to terminal 2. I pulled the E-stop button, and tried forward and reverse: all positions worked normally.

Unable to leave it alone, I decided to grind some plastic off the drum beside the recessed  terminals so that I could attach the short wires from the base of the drum instead of from the side. When I connected the switch again, it didn't work in forward. Darn it!! I retested the connection with the meter:  there was now no connection from the quad to terminal 3 for forward.

I began to search online for a new switch: they run about $125 and aren't available until  April. That wasn't happening. I decided to look inside the drum for problems. As I suspected, there are several springs (10?) and a dozen small parts. I found two small pieces of plastic loose inside, cleaned the contacts, and reassembled. That's the short version. I worked on it for several hours during the day, much of the time spent on my knees looking for springs. I did get to view how the contacts move as the shaft is rotated between positions. Finally, I got it reassembled and tested the contacts. BINGO. The circuit from the quad to terminal 3 was complete.

The wires to the switch barely extended to the open side of the switch housing. During testing, I extended the short wires with 5-inch leads screwed to the lathe wires. Before final installation of the switch,  I unscrewed the housing from the side of the gearbox and was able to pull the cable out about 3 inches, which enables easier connecting without extensions.

I installed it to the lathe. The motor and spindle ran normally. I was elated. But it's a mystery to me why the working connections changed. Maybe the broken bits inside the switch were involved. I might should buy a new switch soon.

I know that this story might be a bit long-winded, but I wanted to share my adventure in electrical repair.


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## JimDawson (Feb 20, 2016)

Those drum switches are a PITA to work on.  I had one apart a while back, I think it took about 6 hours to get it back together.  I wound up working inside of a plastic bag to contain the springs as they flew out.  I got that one from Ebay, for about $20.  The only difference between it in the stock Jet switch is that one of the cams needs to be turned to a different position.  I almost had it, then my hand slipped and the damned thing exploded.  Next time I'll glue the plastic covers in position so they keep things contained, then it would be an easy job.


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## TLW (Feb 22, 2016)

_"They were all very nice, but they couldn't provide much assistance. It was frustrating for me, but I can understand that nobody wants to give wiring advice over the phone."_

   That's because they don't make any money giving advice over the phone. I called today with an electrical question and was told to drop off the motor, waite a couple of days and they would see if they could fit it in....typical electricians! I worked with them all of my working carrier and I guarantee you, you would get the same answer out of any one of them.....That is unless they owed you a favor then things were a little different. I always made sure they owed me a favor!


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