A follow-up to my recent “Review.IT” article is in order. This is the one where the load-cell had a wire pulled off of it. After some inspection of the load cell – that is, after removing the silicone compound that covers much of the strain gauges, I could see that everything else was intact. If I wanted to do the repair, all I had to do is to connect the yellow wire and then put a blob of silicone sealant on it.
Sounds easy, doesn’t it – except that the pads are very small and the wire is very thin. I put it onto a holder that allows the load cell to be held by clips, then positioned a magnifying glass over the load cell. In this way, I could clearly see the pad that I was soldering to, and of course the yellow wire. This was done in due course – then the other three load-cell wires were connected. All joins were then covered in heat- shrink.
The other tension head came in as expected – so using this one, I was able to determine the load-cell connections. On inspection, the white goes to green, black to red, yellow to yellow (which was still connected) and red to black. The photo above shows the heat-shrink in place, but not yet shrunk.
Here is the load cell and connector mounted back into the tension head with the chain re-attached.
Here is a close-up of the mounted load cell – I had to replace both of the screws that hold it to the chain and the carriage because the old ones had been stripped – I think because the original screws were not strong enough – hopefully, these ones will last longer.
Now a final photo of the completed unit attached to my test bench ready to have its calibration checked and adjusted if needed.
By the way, notice how the blue gripper assembly doesn’t yet have the gripper installed? The reason for this is that I had to modify the assembly because the fastening screws were bent, by going through a 6.4 degree bend – that is the slope of the assembly relative to the horizontal. The holes drilled and counterbored in the assembly were perpendicular to the assembly, but were not lined up with the vertical holes in the mounting.
I put the gripper assembly into my mill and adjusted it to have a 6.5 degree slope, then used a 10mm end-mill to do the counterbore. This was followed by a 6.5mm drill to ensure that there was a vertical hole going through the assembly at the right angle. After doing this, the mounting screws can now be tightened up properly without having to bend in the middle.
The next tension head to look at is the one that came in, apparently had been smoking – and the transformer looks like it has been cooked, with the varnish having boiled out of it.