DC - DC Converter PS connected to A/C by mistake - Page 1
Forum section: electronics / repair

author: gobiking
author_rank: Newbie
timestamp: February 26, 2021, 07:56:11 pm
content: Mean well sd-1000 series PStakes 70v to 120V DC input and produces 24v outputSomeone who shall remain anonymous connected this to a/c 120v by mistake.1. Initial investigation - I found the ceramic fuse - 25A 250V, 6.3mmx32mm had not continuity. I ordered a few off ebay.What should I look at next?Here is the link to the item:https://www.mouser.com/ProductDetail/MEAN-WELL/SD-1000H-24/?qs=umBTOZqEewgZhsUk1BeSyA%3D%3D

author: bob91343
author_rank: Super Contributor
timestamp: February 26, 2021, 08:37:19 pm
content: With luck, you may have it working with a new fuse. In the meantime you can short the fuse and connect a current limited power supply to see what you get. If you don't have one, use an Ohmmeter to see if you measure a short at the input. If so, you need to clear that and it's probably some failed components. If not, you might be fortunate.

author: Per Hansson
author_rank: Unknown
timestamp: February 26, 2021, 08:41:42 pm
content: The best way to test a unknown power supply is to connect an incandescent light bulb in place of the fuse:If it lights up the power supply is still shorted...

author: fzabkar
author_rank: Super Contributor
timestamp: February 26, 2021, 11:39:53 pm
content: Measure the resistance between ground and the load side of the fuse. If there is a short, check the chopper transistor, or similar.

author: TheMG
author_rank: Frequent Contributor
timestamp: February 27, 2021, 12:20:09 am
content: Any electrolytic capacitors on the input side would not have taken kindly to the AC voltage.With any luck, the capacitors presented sufficiently low Xc that the fuse rapidly blew and spared the rest of the circuit from damage.Only way to know... Start probing around and check for anything shorted.If you've got a bench power supply with adjustable current limit handy, now is the time to use it.

author: gobiking
author_rank: Newbie
timestamp: February 27, 2021, 05:45:45 pm
content: My current PSs all max out at 60VI will buy a DROK Boost unit, will this do?https://www.droking.com/900W-Power-Supply-Module-DC-8-60V-to-10-120V-15A-NC-Voltage-Regulator-Adapter-Boost-Converter-Constant-Voltage-Current-Driver-Module-High-Precise-Adjustable-Output-48V-24V-12V-DC-Power-Supply-with-LED-Display-Voltmeter-AmmeterThe fuse was a fast bow fuse, I am going to take apart the case today and post more pics.Thanks!

author: gobiking
author_rank: Newbie
timestamp: February 28, 2021, 03:08:29 am
content: Here is a pic

author: TheMG
author_rank: Frequent Contributor
timestamp: February 28, 2021, 07:26:34 am
content: While your 60V supply might not be enough to get the power supply fully operational, it's probably just enough for it to at least fire up without a load there's usually some tolerance above and below the nominal ratings where it will still work. At the very least, it would tell you if there's any shorts or abnormally high current draw on the input.I see a 470uF cap there, that would present an impedance of just under 6 ohms at 60Hz. That translates to about 20 amps at 120VAC, not enough to blow the fuse by itself. There is likely damage to some other components, and even the cap itself may have been damaged.

author: ogden
author_rank: Super Contributor
timestamp: February 28, 2021, 08:10:09 am
content: Quote from: gobiking on February 28, 2021, 03:08:29 amThere's reverse polarity protection diode which blows fuse when "activated". Exactly that happened during negative AC mains cycle. Replace blown fuse and very likely supply will be fine.

author: Haenk
author_rank: Super Contributor
timestamp: February 28, 2021, 01:54:11 pm
content: RY1 looks damaged to me (molten plastic).

author: CJay
author_rank: Super Contributor
timestamp: February 28, 2021, 02:58:39 pm
content: Quote from: ogden on February 28, 2021, 08:10:09 amThere's also a good possibility the diode is now short too. Definitely worth checking before applying power again.

author: gobiking
author_rank: Newbie
timestamp: February 28, 2021, 09:10:37 pm
content: No short from load side of fuse to groundThe diode - forward bias - 0.6Reverse it starts at 1.2v and climbs up to 2.9v and then OL.The relay RY1 has some assembly glue on the sideThe fuse looks like it is pushed into the metal frame that is soldered to the boardI am guessing if I take one end off I can twist the fuse out of the frame ??I don’t have run absorption wire I am getting some off Amazon to remove the fuse .

author: TheMG
author_rank: Frequent Contributor
timestamp: February 28, 2021, 09:53:32 pm
content: The end caps can be difficult to remove from the fuse, they're not really meant to come off, they're pressed on at manufacture. You normally buy the whole fuse as a unit with leads.

author: gobiking
author_rank: Newbie
timestamp: March 01, 2021, 12:20:23 pm
content: ah ha,I had a senior moment and I bought the regular fuse, arrrgh6.3x3225a250vfast blowcan't find any with pigtails

author: CJay
author_rank: Super Contributor
timestamp: March 01, 2021, 12:26:07 pm
content: Quote from: gobiking on March 01, 2021, 12:20:23 pmYou can, with a bit of carefully applied force, pop the pigtails/caps off and put them onto a new fuse but you need to be sure they're making good connections