Help identifying Potentiometer

Machine is new. Checked resistance between the middle leg against the outer remain constant across the range of switch. With occasional drop outs. Does go to zero in the off position. Which could mean board has issue but I think pot is a issue for sure. I don’t want to wait two weeks on a $10 part to find out.
 
The greater Knoxville area should have someone who carries electronic parts. I found this place

Home

www.shieldselectronics.com www.shieldselectronics.com

but didn't see components offered. There are lots of PWM controllers on Amazon but I think your first move should be contacting the seller and reporting the issue with eBay.

Good luck,

John
 
My gut is telling me 4.7K ohm mostly because all the ones I find online with a "7" after the K are 4.7K ohm but the 9K measurement end to end tells me more like 10K ohm. Probably anything from 4.7K - 10K would work.
 
Talk about crappy labeling. This pot looks like that it was made in Lower Slobovia. Potentiometers of that style usually come in even number ratings such as 1k, 5k, 10k 25k. Well, you get the idea. Measure across the two outer terminals with a ohmmeter. I bet it is near 10k, maybe 5k. 1/2 k off is not a big deal. I believe that these pots in the control circuit is a linear pot. You don't want a log style, those are used for audio volume control circuits. If you can, get a Allen Bradley type J. I think that they are still made in U.S. (someone correct me if I'm wrong)
 
Not saying the pot isn't a bit flaky, but my hunch says the controller board is misbehaving. Some of them do have an annoying "feature" which requires you to turn the knob all the way down before the motor will start, but it sounds like yours is acting strangely even so
Definitely notify the vendor, see what they say.
-Mark
ps: at www.olduhfguy.com there is a troubleshooting section that might be helpful
 
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An important parameter in selecting a potentiometer is the taper. They typically come in one of three styles, linear, audio, and reverse audio. A linear taper pot will be at 50% of its total resistance when the pot is rotated half way. An audio taper pot will be at 50% of its resistance when the shaft is rotated to about 85% of its CW travel. A reverse audio taper pot will be a 50% if its resistance at about 15% of its travel. For an application like a speed control, you want a linear pot so the operating range isn;t compressed

As to type of resistance element, a wirewound pot is the the least sisceptab;le to wear from the wiper. The two issues with wire wound pots are they are limited to lower resistance values and the resistance necessarily increase in step as the wiper slides from one winding to the next. This can be a problem if you want tight resolution. Other types of resistance elements include carbon film, conductive plastic, and cermet. Of these, the carbon film is least reliable but cheapest. It is best relegated to set it and forget it type application. Cermet pots are reliable. I haven't evaluated any conductive plastic pots so I can't comment on their reliability.

Another parameter is the power rating. As with any resistor, when the power rating is exceeded, the pot will overheat and can fail prematurely. This shouldn't be an issue with the OP though.

Finally, comes the resistance value. If a pot is operating as a variable resistance or rheostat, this is important. Too low a value will limit operation while too high a value will limit the useful range of the rheostat. Operated as a potentiometer or voltage divider, the resistance is less critical as the voltage out it equal to the product of the voltage in and the fraction of rotation and independent of resistance. Resistance can come into play regarding the associated electronic but usually isn't a problem as long as values are reasonably close to the design value.

edit: I should add mechanical characteristics such as mounting type, shaft style, and single or multi turn. Also, open design vs. enclosed vs sealed.
 
Thanks for all the information. I bought a 10k potentiometer locally. Seemed lightweight but worked. Controlled the rpms. The lathe would only reach 830 rpms. Supposed to be 1440. Is the 10k potentiometer to high or to low. Old one measured 9k on multimeter.
 
There may be a series resistor to limit the upper end rpm. Id you're lucky, it's adjustable in which case you just set it to bring your maximum rpm to 1440. Ifr not you can increase the maximum rpm by decreasing the value of the series resistor. The easiest way is to add another resistor in parallel with it. When I do that, I just tuck the leads of the additional resistor under the existing resistor leads and add a bit of solder. Don't dolder the reswistor in until you have determined the proper value. The new resistance value will be Rnew = (Rold x Radded)/(Rold +Radded).
 
The best for the best answer goes to Matthewsx. Other issues have popped up. Olduhfguy confirm that I am having control board issues. Even offered to send me 4 or 5 other bad ones free. Stated a lot of Machines are being shipped the the control board I have and a large number are failing. I ordered a US made board from him today. Thanks for all the answers. Learned a lot from them which I love. Old but still learning.
 
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