0
\$\begingroup\$

I have this bench psu. (datasheet, manual). It has worked wonderfully so far, but my one problem is that the current adjustment knobs are only 1 turn, while the voltage knobs are 10 turn. I want to replace them with 10 turns, but I before I start soldering things on my brand new power supply, I want to make sure I am going about this correctly. How would I do this mod? The pots in it right now are 10k 1 turns.

\$\endgroup\$
8
  • 2
    \$\begingroup\$ Desolder, remove, put in, solder, profit. \$\endgroup\$
    – PlasmaHH
    Commented Sep 26, 2017 at 12:09
  • \$\begingroup\$ Is this all i have to do? nothing else to worry about? \$\endgroup\$
    – user163229
    Commented Sep 26, 2017 at 12:12
  • \$\begingroup\$ Note that the datasheet gives the CV regulation as 20mV on 32V, or 1 in 1600. The CC regulation is 50mA on 5A, or one part in 100. So changing to a 10-turn pot will probably give a false sense of accuracy. That is probably why it wasn't fitted to start with. \$\endgroup\$
    – Jack B
    Commented Sep 26, 2017 at 12:13
  • \$\begingroup\$ sorry, but just to clarify is this saying that if I set the current to 5A, there could be up to a 50mA deviation? is the 50mA constant, or is there a percentage tolerance? \$\endgroup\$
    – user163229
    Commented Sep 26, 2017 at 12:19
  • 1
    \$\begingroup\$ You should measure the stability of the CC mode first, especially if it drifts as the PSU warms up. If this is the case then the 10 turn pot would only offer an illusion of accuracy. If it stable though, go for it ;) \$\endgroup\$
    – bobflux
    Commented Sep 26, 2017 at 16:54

1 Answer 1

0
\$\begingroup\$

A 10k 10turn pot should work. If you want high stability over time, you want a low temperature coefficient. Otherwise, as the potentiometer gets hot, you might experience drift.

In addition: while I think this is no longer the case on modern power supplies, I remember that some older power supplies would pass a not-insignificant amount of current through the set potentiometers - enough to damage smaller potentiometers. Make sure to get the right power rating.

\$\endgroup\$
2
  • \$\begingroup\$ I opened up the psu, and the voltage adjustment pots appear to be these, but the ones that came in the psu dont have a power rating. I'm assuming 2 Watts should be fine, but am I underestimating this? \$\endgroup\$
    – user163229
    Commented Sep 26, 2017 at 12:16
  • \$\begingroup\$ sorry, i cant post a picture right now, I'm away from home. \$\endgroup\$
    – user163229
    Commented Sep 26, 2017 at 12:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.