Help reassembling a Delta disc-belt sander with a potential relay

[iadr]

I have a Delta 31-695. I've used it about 2x a year for 30 years.
About this time last year it stopped "releasing" the start winding a second or so into use, as it should do. Got busy, couple months go by. I took it apart and I saw the relay was screwed together with a ultra thin screw, and it had vibrated apart. Because it's in a dust proof enclosure the nut was not lost. To be safe- as the contacts looked terrible on the OEM relay, I ordered a universal "SUPR" potential relay off Amazon, because a Google search found a wood working forum where a guy linked to it saying it was used in repairing his. Got busy, couple months go by, and I go to assemble it for use. I picked at the deposits on the contact with my fingernail and the worst one popped right off and the other bad looking one cleaned up well. I reassembled the OEM relay.
I realized I was not clear how it connects. There are three wires that go to it. A red coming out of the capacitor, a black from the 120v switch, and a black to the motor.
I found this wiring diagram, but apparently I don't have the experience to interpret this.
So if you want to see what it looks like, it's a yoke with two contacts and a free floating "piston", and is wrapped in copper.
November 2023 I posted elsewhere on this forum, and did not get the help I need.
I don't need you to take time out for a long explanation of how a potential relay works (or current relay- some have argued that's the correct term). I get that. I don't get what I'm doing wrong, or what my diagnosis process should be. I've tried local power tool repair places, and they blew me off.
I really need to get this unit operational ASAP. It's three wires and nothing is working.
I can get the tool to start up but it sounds to me (it's been a year since I last heard it run) like the start winding is still stuck on.
I switched the two wires- red from the capacitor and the black switched from the power switch, and stays the same.
Things that makes me convinced the start windings are staying on is:
- it sounds "rushed" - not laboured but going too fast
- there's a "crack" like a .17 rifle when you turn it off, and it stops more immediately than I recall it doing. Neither of these are normal.
- leaving it on, no load, minute or so, I get a sweet stench, after shutting it off. Not burnt windings. I do know what burned gylptal smells like & not that. I can't tell from where, but wondering about the capacitor? I touched around on the motor and no where felt warm. Capacitor is in a plastic sleeve, but didn't seem warm (I'm cautious due to shock hazard?).

I tried the SUPR relay but no combination of connecting to it does anything. No start up of the motor, no hum, no breakers kick off, nothing. If you were to connect it 1, 2, 5 which is which? I have: A red coming out of the capacitor, a black from the 120v switch, and a black to (from?) the motor.

I really need this thing operational badly. AFIAK I do not have a meter to test the capacitor. If the motor is starting fine, I don't see it as the issue. Could it explain my symptoms?

How can I help you to help me?

 

[micromind]

There needs to be some sort of a spring that keeps the contacts open unless forced closed by the coil. It might be built in to the piston.

Are the contacts open when not energized and do they open when the motor is up to speed?

When the motor starts, there should be a small blue flash across the contacts. If not, the start winding is not disengaging.

Also, the 2 black wires (power and motor) need to be connected to the terminals where the coil wires are connected (it doesn't matter which is where) and the red wire goes to the terminal that the coil is not connected to.

 

[iadr]

There needs to be some sort of a spring that keeps the contacts open unless forced closed by the coil. It might be built in to the piston.
- This puzzled me. No, I saw no visible spring. I'll take it about for the 20th time and look again. I get that the magnetism pulls it one way, but without power the "piston" just rattles back and forth when you shake it. I'm 80-90% sure a spring didn't get lost, but maybe? That makes sense the more I think about it.

Are the contacts open when not energized and do they open when the motor is up to speed?
- I don't think they open- 80-90% sure not, but can I tell using a continuity setting on a meter while it's running? The design means the relay only functions when assembled.

When the motor starts, there should be a small blue flash across the contacts. If not, the start winding is not disengaging.
- it's sealed when assembled.

Also, the 2 black wires (power and motor) need to be connected to the terminals where the coil wires are connected (it doesn't matter which is where) and the red wire goes to the terminal that the coil is not connected
- this interests me. OK so the yoke side (foreground in my pic above) gets both blacks, and the red is on the single terminal at the bottom (furthest away from the camera?) I don't recall trying that config. I'm going to be thrilled and yet briefly upset if that is the solution. It'll be a few hous before I can test it that way.

So it's either missing a spring, or hooked up wrong. Let me look at it again. I'm just in a tough spot in life and the pressure is preventing me from being clear headed.

 

[dave*99]

I have some old Delta equipment so I found this thread interesting. It seems the relay armature returns open by gravity. Here is what I read:


"I have one of these units - same problem.

These units do not use a centrifugal switch like most ac motors.
Instead, the start relay depends on gravity to work. The inrush current is high causing the relay armature to raise up and make contact for the start windings. Then as the motor picks up speed, the current draw is less and the relay no longer has enough force to hold the armature up. It is supposed to fall and disconnect the start windings. Unfortunately, when the machine is loaded heavily, the relay engages again and the motor stops. When this happens, turn off the sander fast to prevent motor burn up.

DELTA NEEDS TO SOLVE THIS PROBLEM AS THERE ARE SEVERAL POSTS BY PEOPLE WHO HAVE THIS PROBLEM. AND --- DELTA NO LONGER OFFERS THE START RELAY AS A REPLACEMENT PART!"


The quote is from post #17 in this thread:

https://control.com/forums/threads/120vac-capacitor-start-motor.10236/

That said, when testing your motor, be sure it is oriented in the proper position so gravity can do its job. I did notice the schematic for the relay has the word UP printed in it.

I also think the 2 black wires are not interchangeable. Based on your photo with the labels you placed, it's possible you have the 2 black wires reversed. I can't swear to it. I think the red is correct.

 

[iadr]

oh ... for pete's sake... it never even occurred to me the orientation of the relay matters.
That would explain no spring, and how it rattles when shaken.
I paid no attention to its orientation. In fact most of the "tests" I've done were with it out of position, hanging off the wires.

 

[iadr]

Craftsman Table saw Start relay Question

forums.woodnet.net

Per post 7 there,
If it's gravity "return", then I should be able to test it with no power running to it with a simple continuity test by inverting it. I think I'll try that as step "0"
I just looked at a pic of the OEM relay and there is "up" cast into the housing. Grrr.. I read that but didn't understand its importance.

 

[dogdog]

it’s not the end of the world. Lots of old refrigerator uses these starters. Even you tube have them on how to manually start it with push button switch.

That particular switch looks like the GE one I just replaced for the fridge. They still sell that or read up how to use a different type.

$80 though