Colloidal Stirrer Repair

We have been finding that the high frequency switching voltage regulator Integrated circuit (IC) manufactured by National Semiconductor has been malfunctioning when driven by high voltages such as 48 volts at low current levels. It transforms 48 volts down to 2-4 volts to drive the 6 volt stirrer motor. This regulator, LM2597HV-ADJ is located in the left-hand corner.

We must use an efficient high frequency switching voltage regulator rather than a linear regulator, such as LM317, which becomes too hot to drop such a large voltage as 45 v.

Here are the instructions to add one or more essential stabilizing components.

Remove the inductor from the bottom left hand corner of the printed circuit board. It is a small black cylinder marked 330 (33 microhenries) or marked 102K. It is just left of a capacitor of similar dimensions.

Replace it with the supplied larger toroidal inductor with no markings (60 microhenries). There is no polarity to be concerned about with inductors. Be careful not to disconnect the two wires going to the speed control potentiometer, otherwise the 6v motor will receive 48v and perhaps be damaged.

Replace the capacitor marked 100 uF with the larger provided (470 uF), making sure that minus sign is to ground on the printed circuit board,

Replace the integrated circuit in its socket with the replacement provided, if necessary.

We can send you these parts free of charge.

Last edited July 19, 2011