Black & Decker Powersander KA900E Repair

This powersander was brand new, used once only. Next time it was used it worked fine on highest speed but spluttered on lower speeds. Then it stopped working altogether on lower speeds.

I removed the filter housing and its rubber O-ring then the 6 cross-head screws, noting that two are shorter than the rest.

I lifted up the switch and speed control board and was able to inspect the components. There was no visible damage so I began by measuring the resistors.

This was too easy! The resistor marked 4700 (4K7) was open-circuit.

I didn't have one in stock so I removed it and soldered a conventional 4k7 resistor in its place. First I placed some "Kaptan" high-temperature tape on the PCB to eliminate any risk of short-circuit.

I was concerned that the Diac and/or Triac might also be damaged but the powersaw worked fine after this simple repair.

The new resistor has a higher power- and voltage rating than the original and should last the life of the powersaw.

Notes: the Triac is marked T4 1060 and is listed as a T410-600B made by ST Electronics. Note, the Diac is unmarked but ST Electronics should be able to recommend a suitable replacement. I always replace Diacs and Triacs as pairs because if one has failed it probably damaged the other. Luckily, in this case, neither was needed. A very simple repair indeed!

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