Powermatic on-off button replacement

[Dean Center]

We had out annual turning demo for the high school shop classes yesterday and during the middle of one demo, the on-off switch quit working. While we moved everyone to a different lathe, I opened the panel and blew out the switch and it worked again. It was intermittently failing after that, so I think we need a new one. It's been a while since I replaced one of these (Boy, have the prices gone up!) but I'm familiar with the replacement process. When I went to check which switch we need, I saw both ZBE-102 and ZB2-BE-02 switches mentioned. They look pretty much the same. Can someone who knows electronics tell me if one is more appropriate in a 3520A? What about a 3520B? (we have both in the high school shop, and I'll buy a spare)

 

[Edward Kerslake]

I bought a pair of replacement switches to swap out from Amazon. Worked perfectlt

POWERTEC 71390 Safety Paddle Switch - Dual Voltage 110/ 220v Smart Switch for Table Saw, Drill Press, and Disc Sanders, Power Tool Safe Guard​

 

[Dave Landers]

One problem I've had with the switch on my "B" is that the switch itself (the microswitch) still works, but the mechanism to activate it via the big red button gets stuck. It's silly that a several-hundred pound hunk of machine can be taken down by a little sliver of plastic refusing to slide
I blow it out and add some graphite periodically occasionally when it quits working. I've had it quit on me a number of times (and mine is even in a dust free resistant box). But if it were to become really annoying, I too would be looking for a better quality replacement.
The wiring for that switch is just signal to the VFD, so it's low voltage and low current (either 5 or 12V, I forget). But a good quality switch designed to handle line voltage/current might be a more rugged choice. I sorta like the paddle-style switch like Edward posted.

 

[Darryl Fective]

I got tired of having to blow out a poorly designed switch way too often. I replaced both the main and remote switches with simple light switches. It's a $2 fix that has worked flawlessly for years.

 

[Dean Center]

Darryl, if you'd fish that screwdriver out from inside the headstock, maybe it would be less Problematic. BTW, did you notice that someone also stole your speed knob?

 

[Darryl Fective]

Darryl, if you'd fish that screwdriver out from inside the headstock, maybe it would be less Problematic. BTW, did you notice that someone also stole your speed knob?

I was replacing the rheostat as well.

 

[john lucas]

Dissassemble the mechanical part and lube everything. My 3520A was starting to have problems with the switch. turned out to be the mechanical parts and not the micro switch. A good cleaning and lube took care of the problem. That was about 5 years ago and it's still working great.

 

[Dean Center]

Dissassemble the mechanical part and lube everything. My 3520A was starting to have problems with the switch. turned out to be the mechanical parts and not the micro switch. A good cleaning and lube took care of the problem. That was about 5 years ago and it's still working great.

One of the switches gave up since I posted this question, so today I pulled it out and temporarily substituted one from another powermatic that is waiting for a VFD replacement. If I can save the old switch with lubrication that would be fantastic. What material do you recommend for lubing it? Where exactly does it go? (As you know, John, but others may not, there is a center metal post of about 1/2" diameter connected to the red button, and it slides in and out inside a plastic housing)

 

[Dave Landers]

@Dean Center - on mine, there is a little plastic "slider" or "stick" on one side that lets the button operate the micro switch. It's not directly linked to the button, just sits there in between. When this guy gets stuck the button just doesn't operate the switch.
I use graphite powder on it (well, the stuff gets all over everything! but I make sure some gets on that stick).
I don't have a good picture, and I'm not at home otherwise I'd get one for you.

 

[john lucas]

I just sprayed penetrating oil in. Worked the button a bunch of times to get it to move freely.. then wiped off all I could. It was all I had handy that day.

 

[Dean Center]

@Dean Center - on mine, there is a little plastic "slider" or "stick" on one side that lets the button operate the micro switch. It's not directly linked to the button, just sits there in between. When this guy gets stuck the button just doesn't operate the switch.
I use graphite powder on it (well, the stuff gets all over everything! but I make sure some gets on that stick).
I don't have a good picture, and I'm not at home otherwise I'd get one for you.

I know what little red dohickey you mean.
Thanks, John, that's so easy, even I could manage it.

 

[Michael Schneider]

Any Contact switch cleaner once per year is a good cleanup https://www.amazon.com/WD-40-Specia...sprefix=electric+switch+cleane,aps,117&sr=8-4

 

[Bill Boehme]

One of the switches gave up since I posted this question, so today I pulled it out and temporarily substituted one from another powermatic that is waiting for a VFD replacement. If I can save the old switch with lubrication that would be fantastic. What material do you recommend for lubing it? Where exactly does it go? (As you know, John, but others may not, there is a center metal post of about 1/2" diameter connected to the red button, and it slides in and out inside a plastic housing)

Heavy silicone grease is what I use. it is stable and doesn’t collect as much dust as petroleum based grease. Another issue with petroleum based grease is that the oil and soap tend to separate after several years.

 

[Dean Center]

Uh-Oh. Today the replaced switch quit. Or maybe there is an electronic zombie inside the lathe and it's killing off switches. Or, worse yet, maybe it's actually a VFD going out.

To all you electronics wizards out there, HELP! Our local electrical engineer woodturner passed away and we have a serious lack of expertise here. Thanks.

 

[Dave Landers]

On my B, there are 3 wires into the switch. Two actually connected together at the switch - one of them (blue for me) goes back to the VFD (ground), the other to the speed control. On the other side of the switch is a wire going to the direction switch.
If you hook all those together, the lathe should run. Should be able to do that sticking a wire (or the two ends of a probe from a volt meter, etc) between the two little screws that hold the contacts in.


The voltage in there on my B model (Delta VFD-S) is 10v, so basically like handling a 9v battery.

Hope it helps

 

[Darryl Fective]

The voltage in there on my B model (Delta VFD-S) is 10v, so basically like handling a 9v battery.

Hope it helps

Agreed, it's just a low voltage signal circuit to give directions to the VFD. You could unplug the lathe and double check that all the connections are tight on the VFD terminals and the motor terminals. The switches are not a good design for a dusty environment..

 

[Bill Boehme]

We had out annual turning demo for the high school shop classes yesterday and during the middle of one demo, the on-off switch quit working. While we moved everyone to a different lathe, I opened the panel and blew out the switch and it worked again. It was intermittently failing after that, so I think we need a new one. It's been a while since I replaced one of these (Boy, have the prices gone up!) but I'm familiar with the replacement process. When I went to check which switch we need, I saw both ZBE-102 and ZB2-BE-02 switches mentioned. They look pretty much the same. Can someone who knows electronics tell me if one is more appropriate in a 3520A? What about a 3520B? (we have both in the high school shop, and I'll buy a spare)

The best type of switch for this application would be a dry-circuit toggle switch. A dry-circuit switch is one that has a maximum voltage rating of 20 volts dc and a maximum current of 20 mA. Here is an example of a MIL-STD-1344A miniature toggle switch: Carling miniature SPDT dry-circuit toggle switch. I think that a standard size toggle switch would be preferable, but they seem to be hard to find these days. You should also use a rubber boot to help keep dust out.

Alternatively, you could use a regular toggle switch as long as it has never been used for switching anything greater than 20 volts and 20 mA.

 

[Dean Center]

OHSA has been all over the school shop the last few years, requiring cages over all the lathes, even ones not designed for them, for example. If I change the switch, particularly to something not big, red and obvious, I'm concerned the school administration might get in a tizzy. For my lathe at home, the toggle with rubber boot, or maybe even a paddle switch, will be what I look for when the time comes. Thanks for the feedback.

 

[Dean Center]

OK, now that I've got the guts hanging out, one of our club members came to investigate why the new VFD will not work. It looks like the rheostat (speed controller) is not working correctly. Can anybody help with where to get a new one, other than Powermatic? As noted above, I need something that fits the correct hole and looks safe, as this is a high school shop lathe.

 

[Dave Landers]

Hole is a standard size (although there are a couple of standards, so check the specs on what you buy).
The thing you need is a potentiometer. The one in my 3520B is 5KΩ (5,000 ohms). It'll be marked.
I found this on amazon - https://www.amazon.com/dp/B074KCK7X9 - I did not spend more than 15 seconds on that, so ... ya know.
Get something that looks like it was made with some bit of pride, rather than the ones that you can get a dozen for $3.

 

[Bill Boehme]

There are three types of potentiometers:

• wirewound - This is not a good application for using a wirewound pot.
• carbon film - Carbon film pots are acceptable but tend to become noisy over time. This is especially problematic for potentiometers used as a speed control because frequently changing the speed causes accelerated wear of the carbon film.
• conductive plastic - Conductive plastic is by far the best choice and doesn't cost much more than carbon film.

The resistance value is probably 5K ohms as Dave said, but it's not critical because it is being used as a voltage divider. The resistance taper is linear. The shaft is ¼ inch. Check the old pot to see the shaft type (round, half-round, fluted, or something else). The mounting type is threaded with a locating tab.

 

[Dean Center]

Thanks for the replies. I've got one on order.

 

[JJ Bergman]

New member here. Glad I found this thread as I believe my on/off switch has been acting up. Thanks!

 

[John Walls]

New member here. Glad I found this thread as I believe my on/off switch has been acting up. Thanks!

What model do you have? I have a Powermatc 3520C. All my switches acted up, sometimes working, sometimes not. Got to where I could not operate my lathe so took it in for servicing under warranty. They found the control box, even though it looks sealed, is not. It was fully packed with dust. Cleaned control box out, back to working perfectly so my suggestion, if you have same model as I, open the box and clean it out. Just need to peel back the rubber backing on backside, just the 4 corners, remove 4 screws and remove. If you have a different model, you should still check the switches, lathes create a lot of dust/chips. Before attempting this, please make sure lathe is disconnected from it's power source.

 

[JJ Bergman]

Thanks! I have a 3520A. I did try to clean out the switch but no go. I ordered a new switch and I'm up and running. Had an issue with the VFD too but I think I'm back on track. Great forum here