Mill power feed has died; what do I check?

[ARC-170]

I watched the video, thanks. I don't have the light mentioned, but I do have the 10W heat sink thing. Hard to tell what type of potentiometer I have. It looks slightly different than the one in the video.

I have lots of grease on everything as well. Could hardened grease be an issue? It seems fairly soft, though.

 

[ErichKeane]

I watched the video, thanks. I don't have the light mentioned, but I do have the 10W heat sink thing. Hard to tell what type of potentiometer I have. It looks slightly different than the one in the video.

I have lots of grease on everything as well. Could hardened grease be an issue? It seems fairly soft, though.

I doubt it would be the grease. Do you have a multi-meter? Can you turn the potentiometer to 'full speed' and measure the resistance to each wire? If I'm looking at it right, the 'red wire' is probably ground (at least based on position and Blondihacks' video), so you should get signal on both sides. I find it REALLY interesting that instead of the neon light, you seem to have an open plug!

I think the idea of measuring voltage to the big blue and red wires and trying to run it would be a good next step as well.

 

[RJSakowski]

So I would connect the multimeter to the wires coming FROM power to the motor (they are red and blue) and turn the power on, and take a measurement, correct?

Yes, I can spin the motor and the big gear.

Correct

 

[ARC-170]

I doubt it would be the grease. Do you have a multi-meter? Can you turn the potentiometer to 'full speed' and measure the resistance to each wire? If I'm looking at it right, the 'red wire' is probably ground (at least based on position and Blondihacks' video), so you should get signal on both sides. I find it REALLY interesting that instead of the neon light, you seem to have an open plug!

I think the idea of measuring voltage to the big blue and red wires and trying to run it would be a good next step as well.

I might take off the circuit board so I can see it better. Where should I place the wires to measure the resistance? I do have a power light around the rapid feed button that goes on; maybe that's the light?

I did like @RJSakowski suggested. I got about 24V when on and zero when off. BUT, get this: when I re-plugged in the power wires, I tried running the power feed again just to see what would happen and it seemed to work fine.

 

[ErichKeane]

I might take off the circuit board so I can see it better. Where should I place the wires to measure the resistance? I do have a power light around the rapid feed button that goes on; maybe that's the light?

I did like @RJSakowski suggested. I got about 24V when on and zero when off. BUT, get this: when I re-plugged in the power wires, I tried running the power feed again just to see what would happen and it seemed to work fine.

Taking off the board to investigate would work fine. To measure it while running, you could just poke some exposed wire somewhere. The pot you can test by unplugging it (the small 4 pin connector) and just poking in the connector(or loosening it and hitting the exposed pins).

That said, if it is now working, maybe something was just loose that by mucking with it you fixed?

The light near the rapid feed; does it connect to the circuit board where blondihacks' was? If so, it might be that as well, you could check it for resistance too, though now that it works, perhaps not!

 

[RJSakowski]

Beware of intermittents! when you think you have them fixed, they will come back to bite you. I always like to positively identify the cause of the failure. Since it has started working again , it may be due to jostling some connection, making contact again. Try moving some of the wires while the motor is running to see if you can get it to quit.

 

[ARC-170]

Taking off the board to investigate would work fine. To measure it while running, you could just poke some exposed wire somewhere. The pot you can test by unplugging it (the small 4 pin connector) and just poking in the connector(or loosening it and hitting the exposed pins).

That said, if it is now working, maybe something was just loose that by mucking with it you fixed?

The light near the rapid feed; does it connect to the circuit board where blondihacks' was? If so, it might be that as well, you could check it for resistance too, though now that it works, perhaps not!

Here's a picture of the board:


Here's the back:


Here's a close-up of the pot connections. They are all shrink-tubed. Would I need to pull off the shrink tube and disconnect everything? Is that even a good idea? I can re-shrink-tube them if I do.
What am I measuring? Do I put a multimeter lead on one terminal and the other on the other ones in turn to see what the resistance is? The leads don't fit in the connectors, by the way; too big.

Beware of intermittents! when you think you have them fixed, they will come back to bite you. I always like to positively identify the cause of the failure. Since it has started working again , it may be due to jostling some connection, making contact again. Try moving some of the wires while the motor is running to see if you can get it to quit.

I turned it on and it stayed on this time. I wiggled wires, pulled, moved, etc. and couldn't get it to turn off. I had to pull the power wires to the motor to get it to stop and those do not come off really easy. The wires are really crammed in there; maybe something comes loose?

There is no insulator plate between the circuit board and the outer casing, either. What would I use for this? Anything special?

Also, the circuit board was sort of press-fit into a slot in the outer casing; is this some sort of cheap way to do a heat sink?

 

[ErichKeane]

Here's a picture of the board:
View attachment 435096

Here's the back:
View attachment 435097

Here's a close-up of the pot connections. They are all shrink-tubed. Would I need to pull off the shrink tube and disconnect everything? Is that even a good idea? I can re-shrink-tube them if I do.
What am I measuring? Do I put a multimeter lead on one terminal and the other on the other ones in turn to see what the resistance is? The leads don't fit in the connectors, by the way; too big.
View attachment 435098


I turned it on and it stayed on this time. I wiggled wires, pulled, moved, etc. and couldn't get it to turn off. I had to pull the power wires to the motor to get it to stop and those do not come off really easy. The wires are really crammed in there; maybe something comes loose?

There is no insulator plate between the circuit board and the outer casing, either. What would I use for this? Anything special?

Also, the circuit board was sort of press-fit into a slot in the outer casing; is this some sort of cheap way to do a heat sink?

I would check the potentiometer at the connector side (which is the little plug, <Something>3 on the board, above C2), not at the Pot itself. But yes, there should be 3 wires coming off it (I think the red wire is a ground-to-case). You'd check resistance between the 'middle' wire and the outside wires individually, they are usually 'inverted' on pots (1 is 'increasing CW' other is 'decreasing CW'). That said, if the machine works, it probably wasn't the problem, I'm guessing that connection in the middle of the motor wires were loose-enough that when they warmed up they stopped touching as well.

As for the insulator plate, it is probably a good idea, if it was shorting to the case, it could definitely cause problems. You can use anything that doesn't insulate. A piece of plastic, closed cell rubber, a piece of foam/etc would all work. If it were me, I'd just find a cheap piece of stiff plastic (even just milk jug!) and double-side tape it to the back of the board.

 

[pontiac428]

There is also the feed speed potentiometer, which is more exposed to oil creep as a panel mount component. Any cold solder joint in the loop to that pot could make the motor seem hurky. Cold joints are a problem even on the good stuff sometimes. Learning how to spot them is a quick google image search.

Edit: The board looks good to the eye, FWIW. I'd be more suspicious of wire connections and search for any places where tell-tale traces of the magic smoke's escape may be hiding. Even inspect the connections at the stator on the motor, they are hard wire and they have a solder joint to stranded wire to reach the the power supply that can fail from vibration or cold solder joints (again).

 

[ltlvt]

I had a similar problem and I had run it into the over travel limit switch. Since you have already taken it apart, I am assuming you already checked those switches.