It would take an owner to confirm if your unit is normal. I say run it until it dies. Here is some background (but I can't explain the noise.) The inernal device allowing the variable speed is a varrister (sp?) and may go bad, though totally broken is more likely as in any/many electrical things. The initial full-speed could help prevent a burnout, as my friend recommends for ceiling fans because of the 'strain' starting the fan at low speed (truth or fiction?) I have destroyed one sabar saw by depressing the switch slightly and hold it there while the blade was not moving. Lesson learned. Actually, a varister has only 2 leads and therefor your speed controller must surely be a little squear block with several wires. Replaceable but I'd wait until it dies.
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It would take an owner to confirm if your unit is normal. I say run it until it dies. Here is some background (but I can't explain the noise.)
The inernal device allowing the variable speed is a varrister (sp?) and may go bad, though totally broken is more likely as in any/many electrical things. The initial full-speed could help prevent a burnout, as my friend recommends for ceiling fans because of the 'strain' starting the fan at low speed (truth or fiction?) I have destroyed one sabar saw by depressing the switch slightly and hold it there while the blade was not moving. Lesson learned.
Actually, a varister has only 2 leads and therefor your speed controller must surely be a little squear block with several wires. Replaceable but I'd wait until it dies.