Shopsmith Forums

Hi, new member here looking for some advice. I have had my dad's old Mark VII sitting in my basement for nearly 20 years now. I used it a lot when my dad was alive. About 5 years ago I tried to use it, but the motor just hummed and wouldn't turn. I think it even smoked a bit before I shut it off. I took the motor out of the headstock and tried bypassing the switch and it still wouldn't turn even after hand rotating it. I packed it back into the basement and tried my best to forget about it. My dad's been gone about 12 years now, and it's really bugging me that I am not using his machine. I'd like to try and fix it. I could never get rid of it, so it's either repair it and use it, or just let it sit there until I'm gone too.

Should I be looking for a "commonly used" new motor that would work as a direct replacement, or is it worth trying to get the original motor repaired? Not sure which direction to go here.

I don't remember the original three button start/stop/reverse switch ever really working properly. When my dad handed it over to me to use, the switch was stuck in the run position and I would just use an on/off switch at the wall outlet. Maybe that is what burned out the motor over time. I have not had any luck finding this switch, or even a similar replacement switch. I have read posts about rewiring and using multiple switches, but that all sounds pretty complicated. Hoping someone knows of a similar switch, even if it must be mounted differently?

Thanks in advance, and any advice is appreciated,
Mike -

Hi Mike,

Use the following link to go to the thread for Shopsmith Large Format Drawings, Illustrations and More:
viewtopic.php?f=10&t=16113

In the first post there is a link in red labeled My Google Drive. Click on that and find the folder for the Mark VII, along with info about other Shopsmith products. That's a good start for information including some details on the motor and wiring, and the complete manual. There are a few people in the forum with Mark VII machines that will probably be along to help.

Sorry, never even see a Mark VII myself so can't offer any more advice. But welcome aboard anyway, this place is great. Anyone with a little experience with machinery can work their way through most issues but these guys have technical knowledge and experience that goes way above and beyond that.

Ed

Welcome Mike, from a fellow Mark VII owner.

I just bought two Mark VII with in the beginning of the month, I’m still trying to make room to get to working on and clean them up. The first one has a Reverse issue (110v) the second is (240v) and haven’t got to try it out yet.

Thanks to both of you. Appreciate the welcome and replies.
Ed, I will check out the available info at the link provided, very much appreciated.
SkullsquadronX, good luck with your Mark VII's. Hopefully I can get this working again. It will bring back so many great memories.

For working on your Mark VII's you will want to read through Red's (JPG) comprehensive disassembly and reassembly threads in this link.

viewtopic.php?f=10&t=11373

Since different motors were used with the MVII, we need to know which you have. GE? A.O. Smith?, with start relay?. The wire colors differ among the 4 versions. The next step would be to connect the wires independant of the switch for testing purposes to see if the motor WILL run. Smoke is not a good sign if there was very much of it.

Detach the motor pan and motor from the headstock and we can begin this journey.

Thanks guys, I really appreciate the help. So I took the switch apart and I learned a lot reading through the info here. Basically, a couple of the contacts in the switch were gone, and the connectors were a little loose in the plastic housing, which probably created some arcing.

I created new contacts using solder, and glued the contact connectors in tight. I know they wont last, but the idea was to get the switch working good enough to test the motor. The motor would just hum when connecting it direct, as I was bypassing the start capacitor. After reassembly, I continuity tested each connection, and drew it out on paper. If everything worked out I was planning to get a change over switch something like this one: https://www.amazon.com/Taiss-Universal- ... 217&sr=8-1

I connected it back up to the motor and realized that the switch had been modified (bypassed) to only operate as a direction switch. The power contacts were not being used, only forward and reverse. This is why I had to use a separate switch for power. Anyway, it worked! So the motor started good, ran quiet, and the capacitor is good. Unfortunately, the wires coming out of the motor are badly decomposed. I wanted to cut them back and replace them, but they just got worse each time I moved them. I now have the motor apart and I started chasing the wires back to where I could possibly solder on new wires, but I am thinking it may be a lost cause.

I have the C48L2A10 A.O. Smith motor. If someone knows of a replacement please let me know, but I am thinking this is likely over my abilities to swap out the bearings and armature, etc. I'm not giving up, but not really sure where to go with it at this point. Maybe take the motor to a repair shop?

There is a motor rebuilding service specializing in Mark VII that advertises on eBay that seems pretty reasonable. Two way shipping is pricey but since you said this was originally your dad's that may not be your concern. https://www.ebay.com/itm/MOTOR-REBUILDI ... xyi-ZTaZX- Worth reading the ad either way, it offers some information on potential problems where your motor would not be repairable by him. IIWM, I'd take it to a local AC motor shop first in hope of avoiding the shipping costs and because they will probably confirm the wiring before performing service. I don't have a M-VII, but I would guess motor replacement is a tall order. They occasionally come up on eBay, but not often.

There are probably several ways to wire one or two new switches to achieve Fwd/Rev and On/Off functionality. IIWM, I would only use motor rated switches and I would probably use two separate ones. (Normally include a HP rating in addition to amps.) These have design features specifically for induction motors, and the difference in cost is trivial.

- David

This file on how one member repaired his Mark VII switch was posted on the Facebook group.

Shrink tubing to fix crumbling insulation.(keep track of original colors). Maybe a motor shop can do that for you. They could replace the bearings also.


You have documented the switch action correctly except the missing L1 - L1 reverse connection. BTW 5 and 5a should have a permanent jumper.

I would be interested how you expect the taiss switch to accomplish the switching needed. I see a way to control direction, bui not ALSO power on.off.

I consider the 'fix' linked to to be wishful thinking. May work for a while. Contact cleaner simply will not repair poor tension and corroded contacts.