Refurnished and old 150/3 EQ, and there is a problem...

[Nitrous888]

Hello,

I changed the chassis and brushes for an old Festool 150/3 EQ excenter sander, and now there is a spark between the commutator and the brushes, also the armature and the coil is overheating after like 2 minutes of idle usage, so that is not normal of course.

One thing I need mention, I needed to change one of the coils wire because it broke and it looks like a 0.75mm wire, so my electrician friend changed it with 1mm wire and he said it should work, but I read somewhere it should be a problem with the resistance, so we'll change it to 0.75mm tomorrow and we'll see.

So, my question is, do you have some ideas what could be the problem? It making me insane, I tried so many things to make it work, but no luck.

Thank you!

 

[Dongar]

New brushes always arc more until they wear into the shape of the armature. This may be causing the heat. A bigger wire would have lower resistance and should not cause a problem. A wire smaller than the original would.

 

[tsmi243]

What he said. It's not the wire. Either it's normal wear-in, or something went noticeably wrong during reassembly. How hot we talking?

 

[mino]

Hello,

I changed the chassis and brushes for an old Festool 150/3 EQ excenter sander, and now there is a spark between the commutator and the brushes, also the armature and the coil is overheating after like 2 minutes of idle usage, so that is not normal of course.

One thing I need mention, I needed to change one of the coils wire because it broke and it looks like a 0.75mm wire, so my electrician friend changed it with 1mm wire and he said it should work, but I read somewhere it should be a problem with the resistance, so we'll change it to 0.75mm tomorrow and we'll see.

So, my question is, do you have some ideas what could be the problem? It making me insane, I tried so many things to make it work, but no luck.

Thank you!

If you did not use the sander for a long time, check the bearings. The fat in them could have broken down over time and lost its lubing property.

Run the sander for a couple minutes, then quickly disassemble and check which exact parts are hot. If it is the rotor getting hot from the bearings or the bearings from the rotor, basically.

A bigger wire would have lower resistance and should not cause a problem. A wire smaller than the original would.

Not necessarily. That would hold true for a basic voltage-controlled motor. But this sander already has early-gen full-wave electronics and if different wires are used this can cause havoc with how the electronics judges the needed current to provide the tool. Not saying it is the source of the problem, just that "conventional" wisdom does not really apply here.

 

[zjacky]

Hi, the sparking and overheating you’re seeing is likely due to the coil replacement combined with brush seating issues — using a 1 mm wire instead of the original 0.75 mm changes the coil resistance and can cause excessive current, which explains the rapid heating of the armature and coil. Make sure the commutator is perfectly clean, smooth, and correctly sized for the brushes, that the brushes have proper spring tension, and that the Tapered Roller bearings are properly seated and lubricated, because misaligned or seized SL183030 bearings can add drag that worsens current draw and heating. Once you replace the coil with the correct 0.75 mm wire and verify brush seating and bearing alignment, the sparking and overheating should reduce substantially.