Modding a bench power supply - Page 1
Forum section: electronics / beginners

author: josephpate
author_rank: Contributor
timestamp: July 26, 2012, 03:15:34 am
content: I'm relatively new to electronics but I'm a quick learner. I bought a bench power supply before I found Dave's videos on youtube so I ended buying the kind he warns about not buying:It doesnt have a load switch near the output(s), and it has one of those horrible single-turn-pots that make it impossible to tune effectively.I've been considering modding it to add the load switch since that seems relatively straightforward, but I wasnt sure about changing that pot. Would I be able to just remove the one that's there and replace it with a good quality ten-turn-pot? Or is there some added circuitry/wiring that distinguishes them from the single-turn variety? Most of the images I've seen show them looking identical to single-turn-pots, but I figured I'd ask anyway.Thoughts? Hints? Suggestions?

author: Psi
author_rank: Super Contributor
timestamp: July 26, 2012, 03:19:25 am
content: Yep, as long as you get the same specs a single and multiturn pot are interchangeable.The max power/current is normally a bit less with a multiturn pots. There wire is thinner because the multiturn mechanism needs more room.However that shouldn't effect you, the power requirement for a voltage/current control pot is tiny.

author: Monkeh
author_rank: Super Contributor
timestamp: July 26, 2012, 03:27:32 am
content: Quote from: Psi on July 26, 2012, 03:19:25 amNot if you're comparing with the average carbon pot. 10-turn pots are normally rated 2W or more. Carbon pots top out at half a watt.

author: josephpate
author_rank: Contributor
timestamp: July 26, 2012, 03:41:52 am
content: Alright so what type/brand of pot would you recommend? Also how would I figure out what type of pot is in the p.s. currently? take it out and hope it has a model number stamped on it?

author: pickle9000
author_rank: Super Contributor
timestamp: July 26, 2012, 03:50:00 am
content: Bournes makes excellent multi turn potsThe pots should be marked but can be measured.Pay attention to details.- take a pic or write down the hookup- will the new pot fit, is it going to hit anything?- will the knob fit?...mike

author: josephpate
author_rank: Contributor
timestamp: July 26, 2012, 03:54:32 am
content: The knobs on the thing are shit anyway and i'm probably going to replace them too, so no worries on that account.Will probably tackle this project over the weekend, so wish me luck.

author: T4P
author_rank: Super Contributor
timestamp: July 26, 2012, 08:38:48 am
content: Well it will definitely probably be like B100K, maybe another number but heck.B = LinearA = LogAs if power applications will use linear pots ... in fact i believe log pots are going away

author: FenderBender
author_rank: Super Contributor
timestamp: July 26, 2012, 04:16:24 pm
content: At the low resistance settings (I believe), the wattage rating usually drops a bit.Bourns makes good ones, however....I've found that the Vishay/Spectrol 10-turn pots actually have better specs than a comparably priced Bourns pots.

author: Monkeh
author_rank: Super Contributor
timestamp: July 26, 2012, 04:34:09 pm
content: Quote from: FenderBender on July 26, 2012, 04:16:24 pmI don't know about the modern Vishay ones, but the old Spectrols are indestructible.

author: FenderBender
author_rank: Super Contributor
timestamp: July 26, 2012, 04:54:13 pm
content: I think they have to be the same if not very similar. I think the only real difference is the Vishay name slapped on it. It's a good pot. Might take one apart one day.

author: josephpate
author_rank: Contributor
timestamp: July 28, 2012, 05:02:27 am
content: Should've known this wouldn't be easy. It looks like the pot is soldered to the PCB and there's not much room to add a load switchon the banana output (at least not the way I wanted to)May have to back-burner this one for now.