Rheostat

[Tony Wells]

Actually, that's a potentiometer, or "pot". I has a switch piggybacked on it, not uncommon. Is it the switch, or the pot (variable resistor) that is bad? To replace it from a generic, you will need to know the resistance of the element inside. There are a number of places to purchase these things. I may have one myself. If so, it's yours. Is there a marking showing XXX ohms, or anything like that on it?

 

[Starlight Tools]

Why do you feel that the rheostat is bad?

To figure out what the rheostat is, if there are no other numbers stamped into the case, unsolder the wires from one end and read with a ohmmeter between the two end terminals. If zero or infinite then you gotta problem. Should have a value of maybe 5K Ohms. Next read between centre and outside and value should slowly rise or fall as you turn the knob.

Walter

 

[Starlight Tools]

My guess is that it is probably 4700 ohms or 4K7 ohms, so like I just said around 5K but you should double check.

Still most important is why do you figure it is the pot that is bad?

Walter

 

[ChuckB]

Some more info:

http://www.skatelogforum.com/forums/archive/index.php/t-16567.html

 

[pdentrem]

That pot is a B4K7

B = 1/2 watt
4K7 = 47000 ohms also called 4.7k ohm.

It is a common pot but not so common due to the extension out the back for the switch.

The switch is available but not likely at RadioShack. Digikey or many mailorder outfits can supply it complete. You can install a manual switch to bypass the one on the pot if you wish.

 

[ChuckB]

Might cause damage to the circuit by too much initial current on start up. Just a theory though..

 

[Starlight Tools]

Common problem with DC controllers, expecially those used in Treadmills is that they have to be reset to Zero before they can be restarts, If this is the case with this one, it accomplishes both by using the pot with a built in switch.

Walter

 

[Starlight Tools]

Kevin

I did not say that that is how this circuit works, only that it is a common way to wire up the circuits on some controllers.

You may find that separating the switch from the pot may work just fine.

Walter

 

[pdentrem]

Here is one at 1/4 watt rating. You may be able to use if the design of the circuit is conservative.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CT2226-ND


Here is a 1 watt rated control. Oversized for your use.

http://parts.digikey.com/1/parts/1599544-pot-1k-ohm-1w-lug-term-w-switch-381ns1000.html

 

[Tony Wells]

I went through my parts, and found a few 1k w/switch, and a few 1 meg and 5 meg....but nothing of use to you. Sorry I couldn't help. Anyone need some old Zenith radio parts?