I decided to replace the Potentiometer on my G0766, even though it was fully functional after almost 4 years. I noticed that it had one spot in the rotation that had a little pause, so since I had two on hand that I ordered from Grizzly, I went ahead and dealt with it now, instead of being in the middle of a project and risk having a failure. I posted a pic of the replacement on the front page of GGMG, where I clipped the wires for the new hookup. Wiring is easy - green to green [ground], blue to blue, yellow to yellow. Clipping the wires just above the clips on the old pot will give you nice wire pigtails to give you the extra room to use them with the new wires on the new pot. I used wire nuts to connect mine, so it will be easy if ever needed to repair again. I post this to be helpful to anyone who might need to replace the pot on their G0766 or G0733, which are the same.
When I got my G0766 I upgraded the pot to one that was rated for a higher wattage. There's a thread here (maybe a page or two back now). It's worked flawlessly but I haven't put a lot of time on my lathe. I used crimp on spade style connectors so I could also easily swap it out if needed. It doesn't seam like people are having problems like they were so maybe it was just a bad batch and nothing to worry about.
You might be correct Alex. The G0733 18/47 uses the same pot, and they have not had the same issues as far as I know. I ordered the pot I got to replace off the parts list for the G0733, so as you mention it might be the bad batch thing with the manufacture of the new model when it came out. They are supposed to be the same for the 0733 and 0766, but you never know. If Grizzly got the spares for the G0733 some time before they came out with the G0766, then likely it is a good batch.
I know the pot on the G0698 18/47 I got back years ago, and sold to our club still has the original pot in it that came with the lathe, and it has not had one problem, even with the heavy usage I put on it, and now that the club puts on it. Interesting huh?
Pots can get "noisy" (think about radios where you had to wiggle the volume control). They can also (if they are wire-wound) get a break in the small wires of the pot. I had two failures and at least one was a broken wire. The last pot has been working for well over a year w/o any issue. I kind of view the pots as "consumables" - - like sandpaper. I don't stress over the need to take a 10 - 20 minute break to replace the pot anymore. I use wire-nuts and that makes it easy to do a swap. I currently have two spares on hand. When I go to replenish my supply of pots, I'm going to replace with a non wire-wound pot. While it may get noisy, it isn't going to get a broken wire. Roger, if you had a dead-spot, that would suggest that there was some "crud" or oxidation on the wires.
BTW, I love the fact that this forum still exists. When we "Griz" owners have a problem or suggestion, we can post it and share info.
Roger, good point about the pot on the G0733, and funny you should mention it. A few months ago I replaced the pot on my G0733, after six years of service. The original never got noisy or erratic; just stopped working one day. Ordered the new pot from Grizzly, and because they're so inexpensive, and the G0766 uses the same part, I ordered four. Even with $5.99 shipping, the whole order was only $16.99. No problems with the pot on my G0766, but several friends have that lathe also, so I figure I'll already have the parts on hand just in case. That way I'll probably never need them.
Brice, when I was looking I didn't find very many non wire wound pots that were the right shape and resistance. My thinking for upgrading to a larger power rated pot was simply because the wire would be thicker to handle the extra current. Thicker wire should take longer to wear out. There's really only two ways a pot dies. Either it has too much current sent through it and it burns up (unlikely in this case) or the wiper arm wears the wire down and it breaks. My guess is some of the pots probably didn't have enough grease in them and the wire was worn prematurely.
Hi Alex, Your logic makes sense. I was also wondering about dropping the resistance down to, say, 1K or 2K ohms. My logic is that for a 10K pot the wire has to be very very fine. IIRC, when I looked at my last dissected pot the wire was around 0.003. I suspect (but it is just conjecture at this point) that a lower resistance wire may be a little thicker. A while back I did a google search of high life expectancy potentiometers. It seems that some of the Cermet and conductive polymer pots may fall into that category. Wire-wound pots didn't fall into that category. But right now I have at least two new pot spares. So I am set for a while. I'm on pot #3, but the first two went very quickly. The first one started acting up after only a couple of months. Reading about the experiences of others, perhaps Griz had a batch or two of pots that failed quickly. Pot #3 has been in the machine for perhaps 1-1/2 years and is doing fine.
Continued... BTW, IIRC, there is 10V across the pot and the wiper acts like a voltage divider to supply the controller with a voltage proportional to the pot position. So, with a 10K pot, there is only 1 milliamp. (or 0.001 amps) flowing through it. That means that (assuming that I did the math in my head correctly) it is only dissipating 0.01 watts. Not even enough to feel warm. With a 1K pot, the power "jumps" up to 0.1 watts (again, it wouldn't even feel warm to the touch).
