Electronics Guru's?? VS Potentiometer

[kmmcrafts]

So my Excalibur potentiometer ( Variable speed switch ) has been finicky for a long time now.. for a while I could blow air in it and it seemed like it sort of fixed the issue but now it doesn't matter much what I do.. I pretty much run the saw at the same speed all the time with an occasional adjustment based on project at hand.. It started out as just touching the dial to make adjustment while saw running would make it jump to slow / fast until I took my hand off the dial.. and it made it difficult to get a speed I wanted but once there it was fine.. however now it will randomly slow down during cutting.. Not a lot just from time to time but, it's getting more and more common, LOL..

My question, would a electrical contact cleaner possibly work or is the contact points inside the switch? I just have some CLR contact cleaner.. I seen on ebay where there was a special pot switch cleaner.. probably the same stuff just branded specific? I guess I could just try it as the switch is going to be replaced anyway if it doesn't fix it, LOL.. but thought I'd ask..

I see Seyco gets $55 for the switch with the wire harness.. I can buy just the switch on eBay for $1.98 and solder it to the wires so if I replace it that seems like a better deal, LOL

[TAIrving]

It does sound like contact issues inside the potentiometer (pot).  Contact cleaner might help if it is an open pot and if the problem happens to be on the surface of the contacts.  But since you had some prior success with blowing air, it might be a problem of sawdust getting into the pot and contact cleaner might not help with that, might make it worse.  

I question why they would put an open pot on a scrollsaw, knowing that we generate fine sawdust.  But the fact that you had some success blowing air into it seems to say that it is open.  

If you are at the end of line for that pot, ready to replace it, then trying the contact cleaner cannot make it worse, so give it a try.  You might be able to make it work properly for some more time before you have to replace it.  Potentiometers can be finicky creatures.  

If the eBay part is the right part then all you have at risk is your time and $1.98.  

Good luck and let us know what you do and how it works out.  

[BadBob]

There is nothing special about the variable speed pot on the EX21. All it does is change the control voltage. I would not pay $55 for one. I would buy from eBay if I could find the correct potentiometer there. My guess is Seyco's are made up special for people who can't solder.

Why do they use these? Because they can buy them in bulk for pennies.

[BadBob]

Potentometers are cheap. Check this out.

[kmmcrafts]

I replaced one once before on my older Hawk.. not because it went bad but because I broke the knob off trying to repair a problem with the motor and Hawk would only sell it as a set for $350 for motor and controller, LOL.. 

I do believe there are different ohm ratings for them but I don't remember for sure.. I'll pull it apart and make sure the numbers match when ordering the new one if I need to order a new one.. I haven't taken it apart yet.. probably won't until after the holidays.. Just gathering info about it for when the time comes to dig into it..

I do know from experience that it doesn't matter too much if you mix up the wires.. The one I did on the Hawk got the wires messed up and when I put it back together the dial worked backwards.. slow on the dial was actually fast and fast was slow... I took it apart and reversed the wires and now it works the way it should.. LOL 

[GrampaJim]

There are a ton of different sizes (values) of potentiometers.  So physical size matters, but the ohm value is more important too.    In the old days, you could just run down to Radio Shack and buy one.  LOL 

[kmmcrafts]

Yeah, sure miss Radio Shack.. LOL.. 

[OCtoolguy]

Shaft size, length and ohm rating is about all you need. Oh, and how the knob attaches. Push on or set screw on flat side of shaft. You might see if it would be possible to "seal" it in some way. 

[preprius]

Pot features..  ohms, linear vs non-liner, watts.  Physical size is part of the watts. 

when you have it apart send me or us a picture.  If you have an ohmeter, Measure the ohms across the widest pins.

digikey.com

mouser.com

 

[CharleyL]

You will need to know the old potentiometer resistance stamped on the side of the body of the old one and it will need to be a "linear taper", meaning that the resistance between the center terminal and either end terminal changes at the same rate as the shaft is turned. In a DeWalt 788 the potentiometer is a 10K ohm (meaning 10,000 ohm). The biggest problem in finding a replacement is going to be it's physical size and it's shaft size and configuration. DeWalt wanted to sell the whole circuit board and the potentiometer when I needed one for my club's 788 for something like $58 plus shipping, so at the time Radio Shack was still open and I bought one the right physical and electrical size, but with a 3" long shaft, then cut the shaft to the needed length in my shop. 

Another source that caters more to the home hobbyist and small business is Jameco Electronics. When Radio Shack closed I was doing business with Jameco by mail order but I haven't needed electronic parts in quite a while now. A Google Search will find their website and contact numbers. 

Charley

[rash_powder]

If contact cleaner does anything it will only be for a short while.  They wear out, especially when the sit in one place for great lengths of time.  

Open up your control board so you can get a pic of the writing on your pot.  You want the part number if possible.  

Then call up DigiKey, they will help you get the correct component.  They ship quite quickly from Thief River Falls, MN.  Once you have it it is just a matter of un-soldering and re-soldering the pot.  Easy peasy.  

You can try calling them without the part number too, they may have a schematic in their resources, however I would get that number first to avoid potentially wasting time.  

If no part number can be found, you can pull the pot, meter the sweep between the terminals, measure the shaft length and diameter, measure the body length and diameter, and use that info to find a suitable replacement.  Hope you haven't to go that route as it makes things more difficult and takes the saw out for a while.

 

[Jim McDonald]

On 12/5/2023 at 12:30 PM, kmmcrafts said:

Yeah, sure miss Radio Shack.. LOL.. 

As a 20+ year escapee from the Shack, let me say if you match the resistance (ohms) and wattage ratings--you only need to worry about physical size. 

Most (if not all) pots have 3 connectors. The center is usually the common and the outside terms are for whether the internal wiper goes clockwise or counterclockwise. 

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

If you can get a close up picture of the stamping on the the pot or if there are ratings on the board, I'm more than happy to try to decipher. 

Contact cleaner certainly won't hurt. You may have a carbon build up under the wiper where it stays in the same place.

Edited December 7, 2023 by Jim McDonald
Adding paragraph

[kmmcrafts]

Well I decided to take the couple screws out to access the switch. Here is some pictures of what I have. The one on my Hawk had all the info stamped on the switch. This one just has some number and letters on it so I might have to do some digging to find what I need. 
 

I question if the switch is even bad. Not sure if you can see in the photos but there is only two strands of wire even soldered to the one terminal. The others were very close to touching the other terminal. 

[kmmcrafts]

If I'm not mistaken I think this is the right one?

 https://www.digikey.com/en/products/detail/bourns-inc./PDB181-K420K-502B/2564756?utm_adgroup=&utm_source=google&utm_medium=cpc&utm_campaign=PMax Shopping_Product_Low ROAS Categories&utm_term=&utm_content=&utm_id=go_cmp-20243063506_adg-_ad-__dev-c_ext-_prd-2564756_sig-CjwKCAiA98WrBhAYEiwA2WvhOjrh0MN06QG3ToLZvM9d4TpM54uzvbeIf9_bv8MMQEP4wVJdSAmsARoCks4QAvD_BwE&gad_source=1&gclid=CjwKCAiA98WrBhAYEiwA2WvhOjrh0MN06QG3ToLZvM9d4TpM54uzvbeIf9_bv8MMQEP4wVJdSAmsARoCks4QAvD_BwE

Now that I think about it I think this is exact same one I put in the other saw a few years ago..

[Jim McDonald]

I think you're looking at the same thing.

[preprius]

that has a long lead time. 

I might have 1 in my cabinent.

Let me check.

If not there is another electronic component store in San jose. 

[preprius]

The pots in my cabinent are all 10k. 4 are non-linear.  I have qty 10 total.

So this anchor link is a good choice.

 

https://anchor-electronics.com/product/single-turn-panel-mount-pot/

 

A Jameco link ..... 

https://www.jameco.com/z/RV24AF-10-40R1-B5K-Taiwan-Alpha-5K-Ohm-500-mW-24-mm-20-1-315-Inch-Round-Shaft-Solder-Lugs-Linear-Taper-Potentiometer_2268919.html

Edited December 8, 2023 by preprius

[OCtoolguy]

13 hours ago, preprius said:

The pots in my cabinent are all 10k. 4 are non-linear.  I have qty 10 total.

So this anchor link is a good choice.

 

https://anchor-electronics.com/product/single-turn-panel-mount-pot/

 

A Jameco link ..... 

https://www.jameco.com/z/RV24AF-10-40R1-B5K-Taiwan-Alpha-5K-Ohm-500-mW-24-mm-20-1-315-Inch-Round-Shaft-Solder-Lugs-Linear-Taper-Potentiometer_2268919.html

Why do I think you are referring to pans in your kitchen cupboard?

[kmmcrafts]

4 minutes ago, OCtoolguy said:

Why do I think you are referring to pans in your kitchen cupboard?

Maybe a crockpot? Only thing I know of in my cupboard that would have anything to do with electricity, 

[kmmcrafts]

13 hours ago, preprius said:

The pots in my cabinent are all 10k. 4 are non-linear.  I have qty 10 total.

So this anchor link is a good choice.

 

https://anchor-electronics.com/product/single-turn-panel-mount-pot/

 

A Jameco link ..... 

https://www.jameco.com/z/RV24AF-10-40R1-B5K-Taiwan-Alpha-5K-Ohm-500-mW-24-mm-20-1-315-Inch-Round-Shaft-Solder-Lugs-Linear-Taper-Potentiometer_2268919.html

I don't know if these are actual photos of the items you linked to but these "look" like they have a pretty long stem.. also mine has a knurled stem.. though i suppose that doesn't matters because I also have a set screw for the knob...

My brother owns a guitar parts store so I'm going to check with him to see if he has any of them.. One brother sells guitar and speaker parts business and another has a custom guitar cab manufacturing business.. 

  

[OCtoolguy]

4 minutes ago, kmmcrafts said:

Maybe a crockpot? Only thing I know of in my cupboard that would have anything to do with electricity, 

"pots" as in pots & pans.

[OCtoolguy]

2 minutes ago, kmmcrafts said:

I don't know if these are actual photos of the items you linked to but these "look" like they have a pretty long stem.. also mine has a knurled stem.. though i suppose that doesn't matters because I also have a set screw for the knob...

My brother owns a guitar parts store so I'm going to check with him to see if he has any of them.. One brother sells guitar and speaker parts business and another has a custom guitar cab manufacturing business.. 

  

And another runs a sawmill. A very eclectic family.

[kmmcrafts]

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.. 

[kmmcrafts]

4 minutes ago, OCtoolguy said:

And another runs a sawmill. A very eclectic family.

Yeah, I have 6 brothers and 2 step brothers, LOL.. a step brother runs a cabinet shop and builds displays for stores / malls etc.. I'm the baby ( youngest ) of them all, what's that saying.. They finally stopped when they got the perfect one... 

[Scrappile]

Or maybe they stopped because they did not want to chance that mistake again??!!