Shopsmith Forums

Can anyone tell me how to ohm check an on/off power switch for the Mark5?

I think mine is shot.

Sunshine

There should be 4 terminals on the back of the switch. The switch is a double throw double throw switch. The Shopsmith switch has two of the terminals cut off. A DPDT switch normally has six terminals on the back.
Connect one of the leads of the VOM to the center terminal of the switch and the other to the terminal directly under it and with the switch in the "ON" position you should read 0 ohms. Do the same for the other pole of the switch. (NOTE: when the toggle of the switch is in the "UP" position the connection is from the center terminal to the bottom terminal. The center terminal is common to the other two on the same side. Just remember that when the toggle of the switch is UP the connection is from common to the bottom terminal. Each of the three terminals aligned in a vertical column are isolated from the other three. Two completely independent switches on one body. Actually most switches I have found seem to break mechanically before they wear out electrically. If the toggle does not move smoothly that is if there is any grinding or looseness the switch may be bad mechanically.
Hope this is of some help.
Bill V

Sunshine;
In my first post second sentence "double throw double throw" should read "double pole double throw"
Bill

Thanks for the information wa2crk. The switch is bad and I have ordered a new one. Your directions were right on.

FWIW, The four terminal switch is a Double Pole Single Throw(DPST) switch.

If it is a 'toggle' switch, it makes with the operating lever in the same direction as the terminals. If it is a 'lever' switch, the opposite is true.

The toggle switch on my '54 Greenie only has two connections on the back and it looks like an original switch. Oddball or changed out?

sliver wrote:The toggle switch on my '54 Greenie only has two connections on the back and it looks like an original switch. Oddball or changed out?

Older models had a single pole single throw (two terminals) switch. Some were so wired even thought a dpst switch was installed. The internal wiring only ran two wires up to the switch. Newer models are different. Some terminate the line cord on the switch as well as the motor leads. Some 'newest' ones have internal connectors also.

i.e. do not be concerned about the 'greenie' example you have.

Just replaced mine last month. Even for someone who has no idea what he was doing the replacement was simple. Also gave me a chance to clean the inside of the headstock.

I find that the 15 Amp switches do fail sometimes. I have been using 20 Amp 110 VAC 1 1/2 HP motor rated DPDT switches for many years now with no failures. The switches at Lowes or Home Depot are only 15 Amp rated that I have seen.

billmayo wrote:I find that the 15 Amp switches do fail sometimes. I have been using 20 Amp 110 VAC 1 1/2 HP motor rated DPDT switches for many years now with no failures. The switches at Lowes or Home Depot are only 15 Amp rated that I have seen.

Shopsmith customer support helped me diagnose the issue to the switch. It was simple:

1. Remove switch
2. The wires are very long, so remove switch from hole on back of unit
3. Wires come off by pulling straight with pliers
4. Connect dark wires together (dark blue, black)
5. Connect light wires together (white, beige)
6. Apply power, if the unit start it is the switch
7. If not is is the motor

I ordered the switch from Shopsmith for $30.00, but it is on backorder so I have to wait.

Bill where do you get a 20 AMP compatible switch? I really need to finish two projects and don't want to wait. The big box stores don't have switches with lugs or 20 AMP capacity.