Do you have a 30v 5A power supply ? - Page 1
Forum section: electronics / testgear

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: July 22, 2021, 09:04:21 pm
content: Like this one?.....If so, with nothing connected......Condition 1if you have all 4 knobs turned all the way down (counterclockwise), then turn the Far Right (Voltage Coarse) knob clockwise, ....does the voltage on the meter rise or stay at zero ?Condition 2Now....Turn all 4 knobs back down all the way (counterclockwise)Next, turn both the CURRENT knobs clockwise (all the way up)Finally, turn the FAR RIGHT Voltage Coarse knob Clockwise.......does the voltage on the meter go up as you turn the knob or stay at zero?

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 22, 2021, 09:55:53 pm
content: In both cases the voltage should go up.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: July 22, 2021, 10:13:11 pm
content: Quote from: BeBuLamar on July 22, 2021, 09:55:53 pmYou don't happen to have this particular PSU do you?

author: 2N3055
author_rank: Super Contributor
timestamp: July 22, 2021, 10:13:37 pm
content: If you have current limit set to minimum, the zero current, it won't let the voltage rise, regardless of voltage setting...CC led will be on.But if you open current knobs just a little, so CC led shuts off, it will let you rise voltage...It is how it works...

author: duckduck
author_rank: Frequent Contributor
timestamp: July 22, 2021, 10:27:47 pm
content: I don't own one. It is also sold as the Dr. Meter power supply on Amazon. I will point out that this is, as far as I know, at USD57 + tax (delivered), the cheapest linear power supply available new in the USA. I'd be interested in a teardown and review, or at least some nice pictures of the guts. I haven't found a cheaper (delivered) linear power supply even from AliExpress or BangGood.EDIT:Doh! Just checked ebay and it's USD48 + tax, delivered. Wow, that's cheap.https://www.ebay.com/itm/113139856088

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: July 22, 2021, 10:35:52 pm
content: Quote from: duckduck on July 22, 2021, 10:27:47 pmFor years it was my only power supply.Now I have a bench full of better power supplies. But I still really like this one , for all it's cheapness and faults.I had blown this one out about 2 months ago by connecting it backwards to a boat battery. ElectroBOOM style. Magic Smoke released.Since then I've repaired all the damage and it's back up and running, but I can't recall the two conditions posted in the OP and wanted someone who actually has the same one to verify.I have a very extensive cataloging of the components and I'm working on a full schematic in KiCAD.Why would I do this for such a cheap power supply? One word....Learning.Electronics has become a favorite hobby.I've repaired 3 blown Meanwell Power supplies, a 58v battery charger, an inverter, a Bissell battery board and a few other fun things.This one has a fair amount of SMD components on it, a few that I successfully replaced.I never knew electronics could be so rewarding and fun.

author: TimFox
author_rank: Super Contributor
timestamp: July 22, 2021, 10:37:31 pm
content: With most of my vintage linear bench supplies, with the current knob(s) set fully CCW, the output current is forced to zero.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: July 22, 2021, 10:38:51 pm
content: Quote from: 2N3055 on July 22, 2021, 10:13:37 pmGood. Then it seems to be functioning normally, as designed. Time to reinstall the cover.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: July 22, 2021, 10:41:01 pm
content: Quote from: TimFox on July 22, 2021, 10:37:31 pmWell that makes sense.But this is really about voltage in this thread and how the PSU responds when voltage adjustments are moved with current is set to OFF and then ON.

author: MAS3
author_rank: Regular Contributor
timestamp: July 22, 2021, 10:42:40 pm
content: @duckduck:Well, this isn't an issue, it's a feature.As explained by @2N2055: if you set the current limiter to 0.0 A, you'll enable the limiter (and it's indication LED).That will disable the voltage setting.Turn up the current to more than 0 A, and you'll be able to set voltage.The manual should have explained about that too, but like these supplies the manuals aren't the best around.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: July 22, 2021, 11:00:11 pm
content: Quote from: MAS3 on July 22, 2021, 10:42:40 pmExcellent.It doesn't help much that I'm still an ElectroNOOB

author: bdunham7
author_rank: Super Contributor
timestamp: July 22, 2021, 11:55:33 pm
content: Quote from: ThermallyFrigid on July 22, 2021, 10:35:52 pmWell then you should considerwhythe current control behaves that way. And perhaps why it was designed that way.

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 23, 2021, 12:29:57 pm
content: Quote from: ThermallyFrigid on July 22, 2021, 10:13:11 pmNo! My power supplies are not of the same model but if I connect them to nothing the voltage would rise even if the current limit is set to zero.

author: Circlotron
author_rank: Super Contributor
timestamp: July 23, 2021, 01:00:32 pm
content: Quote from: duckduck on July 22, 2021, 10:27:47 pmLinear??? Mine is switchmode. Do they make a linear version in the same case?

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: July 24, 2021, 09:30:08 am
content: Not as far as I know.All of these use PWM and are not linear power supplies.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: July 24, 2021, 09:35:05 am
content: Quote from: BeBuLamar on July 23, 2021, 12:29:57 pmOn the one that this thread is about, if connected to nothing, if you turn both Current knobs to zero, the voltage drops to zero. You have to have some current dialed in to get any voltage.That said, if you have any power supply that uses analog potentiometers for settings, consider replacing them once every few years (or at least cleaning them well)I have found that this unit's reliability is totally dependent on the accuracy of the adjusting pots. Wonky things happen when they lose their accuracy.You need qty 2, B1K pots and two B10k pots for this unit. Very easy job. Buy quality pots.

author: antimatter503
author_rank: Contributor
timestamp: July 25, 2021, 04:18:20 pm
content: Quote from: Circlotron on July 23, 2021, 01:00:32 pmYes, they do indeed make a linear version and a switchmode version.

author: mawyatt
author_rank: Super Contributor
timestamp: July 25, 2021, 04:33:16 pm
content: We have one of these that's a switcher. It puts out so much switching noise on the output terminals and the mains power to be almost useless for anything other powering a motor or light bulbTried a few things to help, but gave up.I wouldn't recommend the switching version, but don't know about the linear version.Best,

author: AVGresponding
author_rank: Super Contributor
timestamp: July 25, 2021, 07:22:20 pm
content: I have the 10A switcher version, and it is indeed hilariously bad.Worth checking the semis are properly screwed back to the heatsinks in these, indeed all the screw terminations too. Many in mine were loose, tightening them did reduce the audible noise under load.