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| Room Temperature Plate |
A friend recently complained to me that one of her Corning Scholar 170 Hot Plates (for her chemistry classroom) was no longer usable. Apparently, an absentminded student had draped the power cable over the top of the hot plate while it was on, which melted through a big chunk of the cable. Yikes!
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| The big takeaway: Don't put meltable materials on a hot surface. |
Replacing the hotplate via the usual science equipment supply company was going to cost over $200! That price seemed absurd to me, so I volunteered to fix the cable. The first thing I needed to do was gather my tools. I ended up using some wire cutters, wire strippers, a box cutter, and some needle nose pliers. I also used a soldering iron & solder, some heat shrink tubing, and a heat gun.
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| Tools. |
First (after making sure that the hotplate was off, unplugged, and cool), I used the wire cutters to cut away the damaged section of the power cable. Then, I made a careful 3" incision along the length of (both halves of) the undamaged cable so that I could peel back the outer casing. Inside the cable, I found a thin paper wrapper, three wires, and some nylon fibers.
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| Try not to slice the inner wires as you cut. Duh |
I cut each of the three wires to a different length. This isn't strictly necessary, but it makes things a little easier when soldering, and it reduces the likelihood that you solder the wrong wires together or that you accidentally short your cable if some of the wire becomes exposed after you have put it all back together.
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| Wires. |
Note that on one side of the cable, I cut the blue wire long and the green wire short, while on the other end of the cable, I did the reverse. This is so that they all end up being the same length once they are soldered back together.
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| Wires with heat shrink tubing. |
If you are using heat shrink tubing, this is the time to slide it into place. I used a piece of 1/8" tubing for each of the three colored wires, and I also slid a piece of 3/8" heat shrink tubing over all three wires as seen below.
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| Big ol' heat shrink tubing. |
Next, I lined up the first of my wires using a Helping hand, and then soldered the wires together.
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| Solder this. |
I then repeated this for the other two wires as well.
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| Soldering complete. |
Then I slid the heat shrink tubing over each of the solder joints, and used the heat gun on the low setting until the tubing shrunk tightly over the wires. If you don't have a heat gun, a hair dryer should work just fine.
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| Sh |
After the wires were soldered and the heat shrink was tightly in place, I carefully tucked the wires back into the outer insulated cover. There was no way for me to reattach the nylon threads together, so I just trimmed them, and then tucked them back in as well. This won't affect the performance of the power cable at all, unless somebody decides that they want to use it as a lifeline when dangling from a 12-story building.
The outer insulating cover of the power cable didn't quite want to hold everything because the wires that I was trying to put back in were a little bit thicker than when I took them out (thanks to the solder and the heat shrink tubing). In order to keep everything tight and contained, I wrapped the cable in a layer of electrical tape. Then, I slid the 3/8" heat shrink tubing over the top, and used the heat gun to shrink it into shape.
Plugging the cable in and cranking the heat dial resulted in fully functional hot plate. The cable did not spark or burst into flames either, so I am going to consider this hot plate fully repaired (but with a slightly shorter cable than when I started).
Total Time: 30 minutes
Total Cost: <$5
Difficulty: Medium Low (requires minimal soldering skill)
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