Vacuum cleaner. We have a panasonic MC-E47electronic which seems dead. It has a speed control

Question

We have a panasonic MC-E47electronic which seems dead. It has a speed control which we nearly always had on full anyway.Have tested continuity through plug, flex and on/off switch and all OK.from then is open circuit through speed control which consist of slide rheostat and mystery small green box (2cm x 2cm x 1cm approx). Across motor there is negligable resistance. Machine is quite old and not worth paying out loads on poarts if it is safe to bypass speed control and connect direct to motor.Is this safe?ThanksAndrew Webber