I bought an LTC3780 buck/boost converter (well two.... idiot me burn one and a half.... those things are expensive!) to make my own Bench PSU!
I already spent 6 hours soldering today I'm getting very very tired.

The converter I bought came with 3 small potentiometers that uses a screwdriver. I wanted to replace it with the big kind,
It has a 204 (200k ohm) for Current control and a 504(500k ohm) for Voltage. I managed to find a 500k ohm but only found 100k ohm for the Current Control. I wanted to use two 100k to not only gain precision but solve the problem (it's very hard to find parts in my country, iw as lucky to salvage the 500k out of something).

so I want to use the 500k with a 100k and two 100k in series for more precision. not just that but I don't have any 200k Pots. is there anything I can do? how do other bench supplies have fine and course controls?!

I tried this:

It didn't work. one of the POTs was just useless.

 

For the 200k pot, if it is used as a rheostat - wiper connected to one end of the track - then you could use a 500k pot with a 330k resistor in parallel. It won't be linear, it will make a greater difference at one end of the rotation than the other, but it will vary the current from maximum to minimum.

 

There are several ways to skin this cat. One of them is to use a pot with 1/10th the ohms of the other pot and put them in series with each other. Albert already mentioned using a parallel resistor to alter (lower) the value of the pot you happen to have or wiring a pot as a rheostat.

You are allowed to ask again if there is something we missed or a specific question you want to get a tight focus on.

 

I already need the 500k for my voltage D:
I shined some light underneath it (no designs online afaik) and it appears that the current pot (200k) is used as a divider and the voltage control pot (500k) is used as a variable resistor (mid connected to the right lead)

 

how do other bench supplies have fine and course controls?

As #12 said there are most definitley multiple ways to skin this cat. One option to look into is multiple turn potientiometers.

One of the issues I see in answering this question is we don't really know what parts you have access to. You can't always create the result you want with the parts you have when your working with such limited access to parts (although sometimes possible). Maybe scavenging some more to find some parts that could possibly be used? Knowing what's at your disposal is always helpful in problem solving like this.

I know it sounds a little crazy but maybe putting 2 of the pots you have in parallel to make it a lower value pot? If you want to go ghetto that may be a viable option.

 

Hey! I got some sleep and with my mind's sanity back I fixed it. My theory did actually work! i must have been too tired and wired them incorrectly.
I used one as a variable resistor and one as a normal one. but sadly as my pot didn't go to exact zero that meant my minimum current limit was now 400 instead of 350 (which If I use constant resistors can get to 160 :O that would have been nice. but I gave up and used a single one! I now put my Custom PSU in a tissue box :| I don't have asses to wood or anything but what I mean is that it's fixed
i don't have 1000k ohm pots so no parallel!

i have 1k and 2k and 500ohm and 100k and a single 500k