How do i slow down a stor plate

[IrishBrewer74]

My friend hooked me up with a laboratory stir plate from her work when they were reducing inventory.

My question is how do I slow it down? On its slowest speed I get a vortex to the bottom of a one liter starter. Here are some shots of the unit and the rather simple control board. I was thinking perhaps adding a resister inline with the rheostat?

Suggestions from the electric people?

 

[Wynne-R]

My guess is that the regulator is shorted or leaky. It’s probably an LM317, which is easy to find, you can even get it at Radio Shack.

That’s probably why you got it. It seems unlikely they would have designed the thing to go from fast to faster.

Other than that the resistor would work, but I’d start with the regulator. If you have a voltmeter, give us the voltages from high to low.

 

[day_trippr]

Could the lack of adjustment be due to a crapped up potentiometer? Out of the few parts in that box, it's about the only thing that could "wear". Maybe squirt some contact cleaner inside the resistor area (unpowered, of course) and work the wiper full scale a bunch of times, see if anything improves...

Cheers!

 

[outside92129]

I have the exact same unit and it works great with a 3" bar. I usually set it between 4-6, not too high as it can throw the bar. I only do 4L or 5L starters though.

 

[IrishBrewer74]

Mine will throw the bar at anything above 2.5. Given thats with a two inch bar, but still.