Electronics Guru's?? VS Potentiometer

[preprius]

My brother owns a guitar parts store so I'm going to check with him to see if he has any of them......

 

Most potentiometers for audio equipment are non-linear.  

[preprius]

yep my cabinent has lots -o- stuff.

top shelf: skillsaw , spotting scope , fishing box is a jewelry tool box, and the travel tool bag is equipped with mostly electrical fix it tools. 

next shelf down: electronic components. including fasteners

next shelf:  miter saw.

bottom shelf: Microscope and other heavy stuff. 

 

[rash_powder]

If you could find a rheostat in the same resistance and wattage that would work too.  

A potentiometer moves resistance from one terminal to the other - like the balance on your stereo; a rheostat is basically just a variable resistor.  So, if you could find a rheostat that fits it would work.  

[OCtoolguy]

Or they bought a tv.

 

[OCtoolguy]

2 hours ago, kmmcrafts said:

So as cheap as these are to buy in quantity.. There is a couple things I don't like about the replacement of these.. One being you have to take the back part of the saw all apart to access the wire plug in.. While that's not a huge job to do.. I'm tempted to build a splice kit so it would be plug and play next time.. Heat shrink connectors under that cover would prevent you from ever having to take that back part of it all apart.. 

I wonder how well a kit would sell if I was to solder the wire leads on and connectors so one could cut their wires and crimp on some connectors so they don't have to take the whole saw apart.. Seyco gets $55 + shipping.. I don't see any reason I couldn't make them like this as a kit to offer.. and at about $25.. 

And another entrepreneur is born.

 

[CharleyL]

"Also, pots are rated linear or audio. Generally, audio pots are more precise."

Not correct. Audio potentiometers do not have a linear taper. They are labeled "Audio Taper" because their resistance is more expotential, meaning that the resistance from end terminal to the center terminal changes faster as the slider is moved across it. You won't be happy if you use one of these. (Accuracy and quality do not change because they are labeled audio taper). The quality of construction is usually affected by the price. There are other special purpose versions with different tapers out there too. Just be sure you are about to buy one that has a "linear taper" label on it when replacing your speed control potentiometer in your saw. If not a DeWalt 788, then the 10 K resistance may be different in your saw. It and the shaft size will then likely the most important information needed.

 

Charley

[kmmcrafts]

Well, sure has been some good info in this topic... I think I repaired the saw without replacing the switch.. I mentioned in the post with the photos that one of the terminals the solder only had 2 strands of wire connected.. and the other strands were almost touching the other terminal.. I think it was vibrating enough that maybe they was shorting out on that other terminal.. I reconnected the other strands on a hunch that this might be happening.. I just ran the saw for about an hour and no issues at all.. Used to be you just touch the dial and the saw would jump from fast to about half speed or slower without even turning the dial.. just touching it would do that.. Now I'm able to touch it and move it.. seems to be working very smooth throughout the range.. I believe this fixed the issue.. 

Somewhat off topic but on solder topic.. In the auto repair industry they do not recommend soldering anymore.. years ago that was the way to do wire repairs but due to vibration and heat cold cycles and age solder with form very small cracks.. and lose a good contact / connection.. I cannot tell you how many digital dash repairs I've had to do on some of the 80's cars.. It's also very common on some Chevy models.. probably others too.. common on the information center in a cars dash.. currently experiencing that on my 2011 Chevy Traverse.. the info center works at night but not in the daytime.. it's due to a weak solder joint on the circuit board in the dash cluster..

All of this auto info is what sparked my interest in the possibility of that being the issue with the scroll saw.. That upper arm where the switches are mounted gets a lot of vibration.. not only from the saw running but raising and lowering the arm.. 

So with that said.. if you have a variable speed issue.. check the solder connections before throwing parts at it that it may  not need.. On the car dashes.. the solder "looks good" however if you remove it and re-solder it they work great.. so there is just micro cracks within the solder that are not visible to the eyes.. maybe under a magnifier or something but not just normal eyesight. It's worth just heating the solder up and remelting it before buying parts..  

[Scrappile]

You see, I am the youngest in my family also.  Two older brothers, and I try to tell they your argument also, I They are not easily swayed. But they do admit I am and always have been the black sheep of the family..

[Scrappile]

You see, I am the youngest in my family also.  Two older brothers, and I try to tell them  your argument also, I They are not easily swayed. But they do admit I am and always have been the black sheep of the family..

Edited December 9, 2023 by Scrappile

[BadBob]

On 12/8/2023 at 2:56 PM, rash_powder said:

If you could find a rheostat in the same resistance and wattage that would work too.  

Since you brought it up, I don't think a rheostat would be suitable for a scroll saw speed control.

• Potentiometer: Typically used for low-power applications such as:
  • Volume control in audio equipment
  • Brightness control in lighting systems
  • Position sensors in joysticks and other control devices
• Rheostat: Typically used for high-power applications such as:
  • Motor speed control
  • Heater control
  • Lighting dimmer switches

Power handling:

• Potentiometer: Designed for low power handling.
• Rheostat: Designed for high power handling.

Internal construction:

• Potentiometer: Typically have a resistive element made of a conductive film or wire.
• Rheostat: Typically have a resistive element made of wire wound around a ceramic core.

[BadBob]

To test a potentiometer.

Measure the total resistance:

• Connect one probe of your multimeter to each of the outer terminals of the potentiometer.
• The multimeter should display a resistance value. This value should be equal to the total resistance of the potentiometer, which is usually printed on the body of the component.

Measure the wiper resistance:

 

•  Move the wiper to the center of the potentiometer.
•  Connect one probe of your multimeter to one outer terminal and the other probe to the wiper terminal.
•  The multimeter should display a resistance value. This value should be approximately half the total resistance of the potentiometer.
• Rotate the potentiometer through its full range, looking for dead spots or other erratic changes. The resistance should change smoothly from maximum to minimum and back.

You can also check them with the power on by measuring the voltage. If I remember correctly, the voltage is only 5 volts DC.

I'm an old-school electronics technician, so I prefer an analog meter for this test and have a Simson 260 just for this sort of thing. However, you can do it with a cheap digital meter.