I bought this adjustable power supply kit and successfully assembled it. I wanted to upgrade the potentiometers to 10 turns so I could have fine control over the current and voltage limits set. Both potentiometers are 10K ohm and I have tested both to make sure they were in that range. For some reason, the output of the board drops somewhere like -0.5V when I try to use the upgraded potentiometers but works fine with the originals. What is causing this?

These are similar to the originals, only without the rear two pins (all i could find)

These are the upgraded potentiometers

  • \$\begingroup\$ User error - incorrect wiring, damaged PCB when desoldering the original pot, etc. I don't think anyone will be able to answer this without more details like photos. \$\endgroup\$ – pipe Feb 27 '16 at 4:55

I'll make a WAG on this- the wiper is typically the rear terminal in 10-turn helical pots (vs the middle terminal on single-turn pots), so if you wired the middle terminal to where the wiper should go it wouldn't work well.

Note that Bourns numbers the terminals 2-1-3 from the back (see the drawing).

| improve this answer | |
  • 1
    \$\begingroup\$ Yeah that was it. I guess i know now for the future to check BOTH terminals in reference to what i believe is the wiper. Much appreciated! \$\endgroup\$ – Daniel Feb 27 '16 at 5:24
  • 2
    \$\begingroup\$ It's not a bad idea to play with the original potentiometers and the new ones with a multimeter set to Ohms mode; by doing this you can easily discover which two nodes are the terminals of the main resistive element, and which is the wiper. \$\endgroup\$ – Kaz Feb 27 '16 at 7:28
  • \$\begingroup\$ As @Kaz says, btw you were lucky the pot was not destroyed- if it's connected as a voltage divider and you turn the wiper to minimum resistance the expensive pot can be fried. \$\endgroup\$ – Spehro Pefhany Feb 27 '16 at 13:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.