Shopsmith Forums

I have a 4 year old Mark V 510
About a month ago I turned my speed control up the high end and at "S"on the scale I heard a pop, smelled electrical smoke and the circuit breaker blew in the shop. I reset the breaker, and was unable to start it, it did the same thing, so I turned the speed control back a very little bit and it started. The same thing happened a second time, so I just stayed below the "S" setting and finished the project. Everything seems fine, good power, no decernable problems.
I have been pretty careful to turn down the speed when Ishut off the motor, I have cleaned and lubed as directed. I can't see or hear anything in the headstock and I cleaned it about a week before this happened.
Any thought on what I should do first?

I read Dusty"s thread, Is that where I need to start?

If I understand your problem, you have an electrical problem that only occurs when you move the speed control to the high end (fast).

If this is accurate, I suggest that you unplug the Shopsmith, open up the headstock and inspect the entire AC power cable within the headstock. The switch is mounted in that general area. If the wires became somehow involved with the speed control mechanism, the connectors could have been moved so as to short against something in the headstock.

If this has happen, you should be able to see the markings left behind by the arcing.

Route the cables so that they have no opportunity to become engaged with the speed control and you should be OK.

Inspect those wires good. A repeat performance is not adviseable.

If it were my machine, I would check the total length of the motor wiring, all the way backwards from the switch to the motor. Remember that little plastic clip on the inside of the headstock - that attaches to the speed control unit. Its purpose is to hold the wiring up and away from the moving parts. When speed is increased the shaft over the control sheave moves quite a bit toward the left (as viewed from the access hole).

Remember to unplug the machine before checking the wiring. If you don't find any visible sign of wire insulation missing, or switch post malfunction, you can use an ohm meter to check continuity while wiggling the wires.

My guess is that the wiring to the switch has gotten caught in the moving control sheave end or in the speed control quadrant assembly. Maybe the attachments to the switch are pulled a bit askew. If you find nothing wrong there, check the power cord attachment to the motor and check your plug. That failing, check the power circuit.

I will start there, I sure don't want to do the routine again, it is pretty nasty!!

dlbristol;

It looks like you have gotten all the advise that you need to recover from this problem.

The pop that you hear, the smell and the blown breaker pretty well tell the story. The AC power line momentarily came in contact with some metalic in the headstock. Since it happen as you were approaching high speed, I'd bet the speed control mechanism and the electrical splices between the switch and the power cord are involved.

After unplugging the headstock from the power outlet, I bet a good visual inspection will tell you whole story.

Follow charlese advise - make sure the power wiring is secured in the plastic retaining clip (inside the headstock near the switch) and you'll be good to go.

Sorry I don't have some good pictures that depict the wires in the headstock and the speed control. Getting respectible pictures in that area is rather difficult. There are some good cut aways that Nick has posted but I was unable to locate them. This won't happen again, once I come across the pictures I need.

Good luck - work safe. Power OFF and UNPLUGGED when working inside the headstock.

Everyone has given you excellant advice as to what to look for. So, I will cover changes that I do when rebuilding headstocks. I always replace the uninsulated wire terminals at the switch with insulated ones I get from Lowes. I only use the black power cord wire and the "not white wire" (blue, black or other color) from the motor to the side of the switch closest to the back of the headstock. I use insulated male and female wire terminal for the white wires and connect them at the motor. These changes are shown in the latest Shopsmith instruction 845034 Mark V Motor Replacement at http://www.shopsmith.com/ownersite/productmanuals.htm. I replace any power plug without a ground and connect the green wire to the motor. I use plastic wire ties every 2" for the wires to the switch and route them up and over the headstock lock rod. I seldom find the little plastic clip so I never use it. I always set the speed to FAST and visually check how close the control sheave and quadrant comes to the wires. With only 2 wires tied together, there is always plenty of clearance. Therefore, I have not had any problem not using the plastic clip. I normally replace the motor wires on the must older 3/4 HP motors.

dlbristol wrote:I have a 4 year old Mark V 510
About a month ago I turned my speed control up the high end and at "S"on the scale I heard a pop, smelled electrical smoke and the circuit breaker blew in the shop. I reset the breaker, and was unable to start it, it did the same thing, so I turned the speed control back a very little bit and it started. The same thing happened a second time, so I just stayed below the "S" setting and finished the project. Everything seems fine, good power, no decernable problems.
I have been pretty careful to turn down the speed when Ishut off the motor, I have cleaned and lubed as directed. I can't see or hear anything in the headstock and I cleaned it about a week before this happened.
Any thought on what I should do first?

I read Dusty"s thread, Is that where I need to start?

One other thing you might look at is the High Speed stop on the control quadrant to see if it is adjusted correctly.

Just thinking.

Thanks guys! This is like having a free repairshop at my house. You were all right on, and the suggested fixes all needed to be done.

My "rookie" mistakes might help some one else avoid this problem. I think I probably pulled the wires out of the clip when I cleaned up the inside of the head stock. Be carefull with the vacume wand. I think the set screw on the speed changer may have allowed the sheve to move to much and contact the wire.

The hole in the insulation was very small, and located on the upper side of the wire, making it hard to see. I pulled the switch, taped the wire, put the plastic loops on the two wires and put everything back in place, re set thespeed changer. It works well. One more reminder to myself to follow the directions.
I would also suggest that if you are new to the MV, the sawdust session on rebuilding the head stock is well worth the time, I learned a lot about how the things work in there.

D.L. - Thanks for your follow-up on this issue!:D