SS "Whirlitzer" clone too fast!

[deci belle]

I'm dealing with a Motion-Sound AR-112 "Sidewinder". SS/100w, has a motorized rotor for the speaker. The amp works ok now, but the speaker rotor isn't responding to my repair attempts.

Does anyone have experience with this unit? Motion-Sound in Salt Lake City isn't responding to schematic requests yet.

I replaced an open (burnt) 1Ω power resistor on the power pcb when the motor wasn't working. Now the motor whizzes at max rpm. The "Slow", "Fast" and "Accelerator" pots aren't controlling anything— nor is the footswitch.

[Jazz P Bass]

You need to find out why the one ohm resistor burnt.
Try to isolate the speed control circuit.
You may find a shorted transistor or triac.

[deci belle]

Thanks, Jazz! I found this link!
YouTube - How to test a transistor

[deci belle]

The two transistors feeding the 1Ω resistor were shorted. After replacing them, the motor works correctly!

[Jazz P Bass]

Glad to hear that you got it.