I am posting this because it may be of interest to G0766 owners who have an erratic speed control. Also, perhaps Grizzly might like feedback from a new owner.
My G0766 had an erratic speed control. As I would be turning up the speed, I had dead spots where the spindle speed would drop to zero. If I wiggled the speed control it would resume. I talked to tech support and they asked me if I had used a digital multimeter to confirm that the potentiometer was erratic. Well, the most likely culprit was the pot (short for potentiometer) and it is an inexpensive part ($2.50). So I told the fellow that yes, I had confirmed that the pot was bad. I didn't want to waste a half hour taking apart my lathe when I was 90 percent sure that the $2.50 part would fix it.
Today I got the new pot. Then I tackled the disassembly process. I immediately found that there was no "service loop" inside of the headstock. (If you've ever worked in an electrical receptacle box with 2 inch long wires, you painfully learned the benefit of having a service loop). That means that when you take out the four screws holding the speed control panel, it doesn't want to come out. What's holding it in? The wiring. I found that if I loosened each of the nuts on the strain reliefs (on the back of the headstock) that I could push the cables through and get kind of a service loop. But the wire between the speed read out and the speed control panel was fixed in length so I found it helpful to loosen the speed readout and I stuck it into the rectangular hole on the top and gained a few inches of length (at the time I thought that it sure would be nice if they had spent about 20 cents and put in a connector....). I found that the speed control box and the speed readout were sealed plastic boxes. I thought that was good because it will keep the dust from getting into the electronics. At this point, I wanted to test the pot with my multimeter. I found that to be a bit challenging because all of the connections were insulated and it was hard to find any exposed electrical connections. But using some sewing needles crammed into the insulated connectors, I was able to confirm that yes, the pot was erratic. The original pot is connected with crimp-on connectors, so if you are going to replace an erratic pot, you'll have to cut out the original one and deal with wires that are pretty short. When you go to re-connect, you'll probably want to use those real small (gray) wire nuts. But, my background is electronic design engineering and I didn't find myself in a new and uncomfortable situation. (I still like connectors and wires that are long enough to make the job easier).
I did a post mortem on the bad pot. I found that the sliding connection between the center wiper and center terminal was noisy. I found that the inside of the pot was NOT clean. I saw little pieces of dust and fibers inside the pot. It should have been 100% dust free. In my opinion, that suggests that the manufacturer of that component is not following standard industry practices resulting in some low reliability parts. I squirted the inside of the pot with contact cleaner and that cleaned up most (but not all) of the erratic performance of the pot. But the connection to the end of the wound-wire assembly was physically too high and that caused the center wiper to lift and the wiper connection to be lost. Perhaps an out-of-spec crimp. But again, in my opinion, it suggested a component manufacturer who isn't producing high quality components. But realistically - - Grizzly is trying to offer a product with high performance and low cost point. So maybe the low cost point is what is what has driven all of this. I recognize that this lathe is hundreds of dollars less than its nearest competitors.
When I completed the replacement, and buttoned everything up, the new system is smooth as silk. It works great.
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Originally Posted by James Combs
I'd like to change my G0733 to match the G0766, to avoid confusion going from lathe to lathe. On inspection, the two switches appear to be wired the same, so the difference must be at the VFD terminals. In the next few days I'll pull the dust covers on the two drives and check that. It may simply be a matter of swapping two terminal connections on the G0733.
DVMs. (Sometimes when the 9V battery goes dead, I just get a new DVM from the store). The discontinuity was so bad that it would go fully open in some spots and stay fully open. If I didn't get such dramatic results, my plan B was to switch to an analog meter. (BTW, I'm a retired EE also). I'm keeping my fingers crossed that the new pot will not degrade like the original one did. Out-of-box or "brand new", the original one would occasionally have a problem and would stop dead, but as time went on it got noticeably worse. This is something that the factory probably could have spotted with a little more QC checking. Come to think of it, I don't recall seeing any QC labels plastered on the machine, like we typically do on stuff like this.
