Not sure if i broke a power supply just now - Page 1
Forum section: electronics / beginners

author: Mp3
author_rank: Frequent Contributor
timestamp: June 06, 2019, 10:45:33 pm
content: Hey everybody. I have a Mean Well RQ-50D which provides +5v, -5v, +24v and -24v.I intended to test it out before i wired it up to the device it was going to connected to, just to be sure all the voltages were correct, so i wired up the AC plus ground in line with a power switch. When i flipped the power switch the green LED on the RQ-50D lit up for a second then went back away. With the switch set to either on or off, i'm not measuring any AC or DC voltage from any of the screw terminals.Did I kill it by feeding power to the power supply without any loads connected to the DC output terminals?Thanks in advance.... I already have another RQ-50D in the mail. I just don't know if i killed it for sure or if i got a faulty unit.

author: JxR
author_rank: Unknown
timestamp: June 06, 2019, 11:01:50 pm
content: Did you happen to check if there is a fuse for 120V/230V on the input? Sometimes you have to change the orientation of the fuse, sometimes it is just flipping a switch.Quote from: Mp3 on June 06, 2019, 10:45:33 pmIf you are not able to measure AC voltage on the terminals then you either have something wired wrong, you tripped a fuse, or something is wrong with your meter. Forget about the DC output at the moment, if you really have no AC input.

author: Mp3
author_rank: Frequent Contributor
timestamp: June 07, 2019, 01:51:47 am
content: Quote from: JxR on June 06, 2019, 11:01:50 pmThank you and for now i'll double check the AC. I had a feeling that i might have damaged a connection on AC inlet, so i'll try wiring AC power directly to the AC input and check again.I'll also take the lid off to check for a fuse, but i dont believe this is one of the models you have to do that on (could be wrong)It looks like this:

author: JxR
author_rank: Unknown
timestamp: June 07, 2019, 01:56:39 am
content: Ok. Just be careful. If your unsure about any thing, such is what wire goes where for the AC line when your connecting it to your cable, please make sure you look at some material online before going further. Double check your wires to the plug end of your cable using the continuity setting on your voltmenter to make sure you know which wire is what. Most voltmeters require you to set it specifically to AC voltage as well, so double check that before taking your measurements.

author: MarkF
author_rank: Super Contributor
timestamp: June 07, 2019, 02:32:24 am
content: You better check the voltages again. The values you listed for the RQ-50D are incorrect.https://www.meanwell.com/Upload/PDF/RQ-50/RQ-50-SPEC.PDF

author: Mp3
author_rank: Frequent Contributor
timestamp: June 07, 2019, 08:58:57 pm
content: Quote from: MarkF on June 07, 2019, 02:32:24 amYou are correct! But that's not the issue, i tried to quote the voltages from memory and mistaken them.Okay, so i found out the problem was with how i wired the AC inlet, i really should have checked continuity there. I have the power supply up and running now.... with one major caveat.All my voltages measured correctly BUT ground and 5v are shorted out (there is continuity). I thought i did some bad wiring, so i double checked all my work, couldn't find anything wrong, and i eventually took all the wires off the Mean Well PSU one by oneuntil I found out that with nothing connected, 5V and Ground (COM) are shorted to each other.At this point do i have to wait for a replacement PSU or something? I am going to look and see if there is a fuse that is blown or something of the sort. This is very strange...

author: maginnovision
author_rank: Super Contributor
timestamp: June 07, 2019, 09:30:02 pm
content: How did you wire it? As far as I know blown fuses don't typically cause shorts unless they blow up and shrapnel shorts something. You probably blew something but I'm going to recommend you toss it and wait for the new one.

author: radiolistener
author_rank: Super Contributor
timestamp: June 08, 2019, 02:10:39 am
content: Quote from: Mp3 on June 07, 2019, 08:58:57 pmDid you connected 220V AC to GND and 5V terminals?

author: Mp3
author_rank: Frequent Contributor
timestamp: June 08, 2019, 03:38:02 am
content: Quote from: maginnovision on June 07, 2019, 09:30:02 pmThere was nothing unusual about how i wired it. I realized I hadn't double checked to make sure there was no continuity between the different terminals when i first powered it on with only the AC power but i was measuring voltage. One thing i didn't do either, is measure for voltage or continuity between the output ground and the AC ground.There were absolutely no debris in the PSU and i double checked that there was no continuity between ground and +5V simply between the wires or any of my solder points - in fact as soon as i wire up the PSU, the voltage test points on the main board show continuity between +5 and ground but as soon as i remove the wires from the psu terminals, no more continuity between ground and 5V.My replacement shows up tomorrow, so i'll hope that dropping it in place of the one i have currently solves everything...

author: Mp3
author_rank: Frequent Contributor
timestamp: June 08, 2019, 03:43:00 am
content: Quote from: radiolistener on June 08, 2019, 02:10:39 amNo sir, it was like this

author: Mp3
author_rank: Frequent Contributor
timestamp: June 08, 2019, 05:11:39 pm
content: I'm bewildered!I just got the new power supply in the mail. First thing i did out of the box, switch the multimeter to continuity andthere is continuity on Ground and +5V on this one too!!

author: plurn
author_rank: Regular Contributor
timestamp: June 08, 2019, 06:17:08 pm
content: Is this continuity measured when wired up and mains power applied? Or when with no mains connected.Despite the continuity measurement, did you try to measure voltage on the 5V rail when live?Just thinking that continuity is measured as a resistance measurement. Resistance is measured I think by applying a voltage and measuring the voltage drop. So you can not measure resistance/continuity properly if the circuit is live.If by some chance your multimeter is putting out about 5V to measure continuity and it is seeing 5V from the power supply, it might be confused into thinking it is shorted when it could just be that it is being measure incorrectly. Just an idea.

author: ciccio
author_rank: Frequent Contributor
timestamp: June 08, 2019, 07:44:42 pm
content: Does the LED lighs up?I the + 5V output's voltage correct?Best regards

author: janoc
author_rank: Super Contributor
timestamp: June 08, 2019, 08:19:56 pm
content: Quote from: Mp3 on June 08, 2019, 05:11:39 pmJust a sanity check - you are measuring with the PSU off and between the COM and +5V terminals, right? Not between +5V and the protective earth (market by the ground symbol, third terminal from the left), right?Because if you are measuring the latter, that could be completely normal, depending on the construction of the supply - this is not a lab supply, it may not be floating and one end of the output could well be tied to the earth pin.If you are measuring between +5V and COM then make sure the value isn't changing and remains stable during e.g. 10 seconds or longer. Otherwise you are only measuring the output capacitors charging from the meter and the meter will indicate that as a short circuit. That will go away after the caps charge up.