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No Load Taking Computer SMPS Restored

By on June 25, 2022
atx power supply repair

how to fix an ATX power supply

This SMPS was attended to in January, 2021. Just see my previous article:

It was again brought to me with the complaint that it was not taking load. This belonged to the hospital where I worked, and the IT-Admin had done a thorough cleaning of inside. I brought it home and checked and found that the SMPS was switching on, but not taking the load of Auto bulb; i.e. voltage dropping. Then disconnected the power supply and discharged the tank capacitors.

As such complaints are mainly due to leaked or weak capacitors, I started checking ESRs and found these to be out of range. I removed one of the tank capacitors and found that it had leaked and slightly bulged out at top and bottom. It is difficult to make it out from the picture.

bad caps in power supply atx

I removed the other one also and checked both in my SMD tester. Just see the results:

bad capacitance value in power supply

Replaced these two caps first and then went ahead and replaced all the other caps except the two I had changed last time (See special notes).

There were no dry solders. But found two yellow wires and two black wires were cut.

cut wires

Cleaned the ends and soldered the four wires in its place. After checking for any man-made shorts, I applied power connecting my SMPS tester and giving a load of automobile bulb. It worked perfectly well.

light bulb test on power supply

Mission accomplished and satisfaction got added to the collection bag. Following is the departing pose given by the retired capacitors:

bad capacitors in atx

Special notes (1) Look at what happened to this SMPS when all the caps were not replaced when it came in last time. Is it not proof enough that replacing all the caps especially on power supplies is absolutely necessary? (2) Always check a computer SMPS thoroughly and look for strained or cut wires, as the computer technicians always pull the connectors by the wires.

(3) Last time I was not having 2200/16V and 470/16V as a replacement for 2200/10 and 470/10. So, I had put 2200/25 and 470/25, which were a bit bulky and were looking odd! But this time I had and I replaced these two. Before putting it back into my capacitor stock, I checked both the values and ESRs, which were found to be absolutely normal. This is important, as these are to be used in some other place.

This article was prepared for you by Parasuraman Subramanian from India. He is 72 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.

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You may check on his previous article on Beware Of Panel Broken Cases When No Display TVs are Taken Up For Service




    June 25, 2022 at 9:58 pm

    Good job sir, thanks for sharing 7

    • Parasuraman S

      June 26, 2022 at 10:26 am

      Many thanks for your encouraging comments!

  2. Anwar Shiekh

    June 25, 2022 at 10:19 pm

    Do you have a preferred replacement capacitor brand/series

    • Parasuraman S

      June 26, 2022 at 10:27 am

      I prefer to use Keltron Capacitors. But some of these are large sized caps. So, I go for imported Samsung Caps that are now freely available.

  3. Albert van Bemmelen

    June 25, 2022 at 10:20 pm

    It is a time consuming job if all questionable and old capacitors need to be replaced in bad smps units. But your article is proof of that! I also have the Mastech MS8910 smd tester and am content with its quality in use. Only the larger lithium cells needed for this tester have a tendency to quickly drain even when not in use. And the extra cells I have in stock are a bit smelly too.
    At least the MS8910 measures capacity and ESR correctly which can't be said of the new and smaller lithion ion chargeable DT71 mini tweezer digital meter that was sold by Elektor as being an ESR tester. But compared to the Mastech the Miniware DT71 is a quite useless digital meter that can't even test smaller capacitors and has no ESR test at all either. In my opinion the new DT71 is just a bad firmware plagued smd tester that is sold for a very high price from Elektor and not worth the money at all! And according to the manufacturer there never will be an ESR firmware adding update although it seemed that earlier firmware versions did have the ESR testing too!

    • Parasuraman S

      June 26, 2022 at 10:29 am

      That is a lot of tips and guidance! Many thanks for your encouraging comments!

  4. Peter Sheldon

    June 25, 2022 at 11:47 pm

    Always look forward to reading your articles, thank you for sharing your knowledge and keep up the good work 🙂

    • Parasuraman S

      June 26, 2022 at 10:29 am

      Many thanks for your encouraging comments!

  5. Lynn Blakely

    June 28, 2022 at 4:39 am

    Another repair jumps into your satisfaction bag, which is bigger than Santa's bag.
    Thanks for another good repair Parasuraman Subramanian.

  6. Waleed Rishmawi

    June 28, 2022 at 2:41 pm

    you are the king of capacitor good job my friend. have a blessed day

  7. Raj

    June 30, 2022 at 8:05 am

    Great Sharing.. thanks much

  8. Humberto

    July 1, 2022 at 10:37 pm

    Thanks for sharing your knowledge

  9. Yogesh Panchal

    July 4, 2022 at 12:40 am

    Good Job! Sir


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