I am working with a Mallory MLC222LS. I have attached a jpeg of the part description from a dated catalog I located via the Internet. This pot/switch controls a 120 VAC laboratory stirrer. An independent toggle switch controls motor on, motor CW and motor CCW. I am assuming the switch on the back of the MLC222LS is associated with no output at zero deflection on the pot.
I have not been able to identify many useful replacement potentiometers. Compact size is important.
Hello Kirchoff and welcome to the forum. The switch you are referencing I could not replicate 1:1, The closest I did get was our non-stocking part 140B00202-ND. This one hits the bushing thread and gets close to the resistance you are requesting, it is a hard miss on the switch though.
3310H-004-202L-ND hits all the requirements except it is a lower spec model used in low amperage applications.
Otherwise the closest I could get to your requirement would be these potentiometers; though the resistance varies on this set (it includes the 3310H part from above).
@Michael_Rudi - Thanks for the response. Yes, I am finding this part challenging to replicate. I do not know if it will be feasible. Could you edit your response so “potentiometers” becomes an active link. I click on the term yet no web page launches as a result of taking this action.
Missed a couple letters there in the link, thank you for pointing it out.
Depending on the circuit type, the 5K Ohm CT2226-ND that Michael linked to has a pretty decent chance of working.
If the pot is being used as a voltage divider (all three contacts used; one end V+, center variable voltage output, other end Ground) then the actual resistance value often isn’t critical. Usually such configurations are used to present a variable voltage to the next stage of the circuit, and typically source little, if any, current.
If it is being used as a rheostat (only two of the three contacts) then there are a few more issues to consider. First is that we do not know the power rating of the original pot. The CT2226-ND is rated for 1/4W, so if the original MLC pot was rated for a higher power, that could pose a problem if the circuit dissipated more than 1/4W. Second is that because the CT2226-ND is a 5K part rather than a 2.2K part, it would have a smaller usable range (less than half the rotational range used), making it more difficult to hit a desired set-point. It’s not likely to harm anything with a higher value resistance, but impossible to know for sure without seeing the schematic of the circuit.
The switch is rated for 3A @ 125Vac, which exceeds the rating of the original, so that part of it should work, at least.
After these discussions it seems best to separate the switch and voltage divider functions. Yes, all three terminals on the potentiometer are involved in this circuit. A potentiometer that appear useful is the cermet Vishay P16 shown here:
https://www.digikey.com/product-detail/en/vishay-sfernice/P16NP222MAB15/P16NP-2.2K-ND/1587862
However, its power rating is only 1W. This would require me to drill an additional hole in the motor enclosure to mount a small switch and a circular pattern is likely to be best. The 3A/125V GC Electronics 35-406-BU may suffice:
https://www.digikey.com/product-detail/en/gc-electronics/35-406-BU/35-406-BU-ND/2041868
I am in the process of sketching the circuit but other priorities exist.
Seems a reasonable solution. I would be extremely surprised if your existing pot were rated for more than 1W - probably only a fraction of that - so the P16 should handle that easily.
In a voltage divider arrangement, the power dissipation of the pot can be roughly calculated by the square of the voltage applied across it (first to third terminal) divided by the resistance of the pot. For instance, if it had 12V across it, it would dissipate about 65mW { (12V x 12V) / 2200 Ohms = 0.065W }.
This may not quite hold true if a lot of current travels out the middle wiper terminal in your particular circuit, but this is uncommon. In any case, a 1W pot is almost certain to be more than capable.
