Old Grob bandsaw.. no torque/ power

(Oh dear.. I think it's a three phase motor... (no cap))

Maybe check the three voltages? Or a bad motor

Never mind. problem fixed. (Sometimes all I need is a smart audience.)

GH

Ah, well, the running backwards strongly indicates it is running on single phase. Check the power switch/motor starter to make sure all 3 phases are connecting. Check any fuses. Look for loose/broken wires. Without knowing what sort of switch/motor starter it has, I can't get more detailed. It COULD be the motor, but could as likely be something external.

Jon

You told us the symptoms, so what was the cause?

We all started out clueless and had to learn somehow.

Certainly the start capacitor. I don't know whether that one has a run cap at all, but starting sometimes backwards says that it is the start cap.

Any clue as to which model? There seem to be a number of models.

I downloaded the manuals for the 4V, and it shows as having a

But if it is a single-phase motor, it should have a start cap, and it will likely be under a bulge cover screwed to the side of the motor. Unscrew the cover (with the saw disconnected from power) and pull the quick-disconnect (push-on) connectors from the cap, unscrew the clamp which holds it, and pull it out. Read the voltage and capacitance (uF) from what is printed on the cap, and go to a motor place to purchase an equivalent. When you put the new one in -- just make sure that one push-on goes to one terminal and the other to the other. (Likely there are two or three push-on tabs for each terminal, and if you push both onto the same terminal you will probably stall the motor. Which wire goes to which terminal should not matter, as this is an AC application, not DC -- which electrolytic capacitors do care about.)

Good Luck, DoN.

Check the three voltages -- and check the three cartridge fuses.

Good Luck, DoN.

Oh sorry, one (or two) of the phases was missing. Someone had been abusing the power plug into the wall outlet... Five minutes with a screwdriver and all was good.

George H.

I've been troubleshooting electronics since 1970. It's rare for the problem to be other than a bad connection.

At the Fort Monmouth Army school the instructors heated and removed an end cap from glass tube fuses and inserted too-short heavy bus wire or paper tags with "good fuse" on them, to teach us to check the power first, and test fuses with an ohmmeter.

Grin... Well someone else here found the problem and 'assumed' a bad cap. after a day I was brought it to help... I sorta bought into to the 'bad cap' idea.

I've been thinking of some sort of trouble shooting guide for people. It seems like a common mistake is assuming the problem is the first thing you think of. And then you follow that idea down some rabbit hole. The first thing to do when trouble shooting is to think of all the things it could be. Make a list if you have to. Then start by checking all the simple things on the list. (simple as in simple to test.) Hmm, well and get lots of data on the problem, that's important. I do trouble shooting on the phone/ email every week or two... you learn to ask a lot of questions.

George H.

But oftentimes the bad cap is the culprit. I live on an island that is mostly rural or semi-rural so we have lots of water wells. And nearly every well has a single phase cap start motor that spins the pump. My neighbor's well has a second pump that is used to pump and pressurize the water for his house because it is quite uphill from the well head and his well is already pretty deep. The motor refused to start and did the typical humming till the breaker pops business. So I told my neighbor to just go buy a start cap. Even though we are mostly rural there is a naval base on the north end and a Home Depot. But nobody had a start cap for his well. Not even the well pump installers. All they could do was order the cap. So I took one out of my band saw which got him water and he ordered two caps so he would have a spare. Eric

When a student asked if there was a troubleshooting procedure the answer was yes, but since it covered every possibility it took far too long to run through. They said they'd found that teaching students how the circuits operated in detail resulted in much shorter downtimes of the communications links we supported.

That worked for them as long as the Vietnam draft brought in science and engineering grads with the aptitude and (more importantly) the patience to learn complex systems. After it ended they had to downgrade to board-swapping.