Saving Computer SMPS Part-10
I have time and again mentioned that I love doing service on SMPS after reading Jestine Yong’s Book on SMPS service. Here are yet other cases, which provide an insight as to how simply we can get back an ATX Power Supply back to work again. Unfortunately, many such lovely SMPS go to e-Waste, as replacement PS is a money making way for the Computer Service Providers. After I started taking rectification action in the hospital where I work, the number of SMPS bought in an year got reduced to almost 1 or 2 in place of almost 12 to 20 pieces. I have made it very economical for the hospital by further bearing the entire cost of repair, mainly because of my passion in servicing these. Having said this much as a prelude let me take you all to what saved these lovely ATX Power Supplies.
Case (1) Mercury KEZ-M200 : After preliminary cleaning, the IT-Administrator brought the SMPS to be for troubleshooting. It was yet another dead case. I opened the cover to see what would all expect; i.e., a bulged capacitor. For a change, this time it was on the primary stage as I found a 330uF/200V burst on the top. Many of you might already know that an electrolytic capacitor is always closed with a top that can burst in case of pressure build up to avoid an explosion. The top portion is generally not a full cover, but cut aluminum sheet pressed down to open and let out the electrolyte and smoke/steam in case of failure. You can see that from the pictures given. Those of you who are interested in reading more about electrolytic capacitors may please see this. As this SMPS had undergone service before, there was no need for me to do any retouch or replacement of other caps. Now see the pictures:
You can perhaps notice the cut (rather punched) can on the top very clearly in the second picture above. I replaced the cap and applied power and found the outputs ok. Just see the pictures below:
Case (2) Foxin FPS500S : This was brought to me dead after preliminary cleaning inside. I did not find any bursting of capacitors or burnt components. The fuse was intact. The ring test showed healthy signs. There were a lot of dry solders with legs of components almost detached from the PCB, which was the main cause for failure. I removed andchecked the Tank capacitors and was not surprised to find its readings. I replaced all the electrolytic capacitors and retouched the entire board very well. Then cleaned it thoroughly. I was happy to see the quality of this SMPS as the wires were fixed with bases rather than direct bare solder. Then I loaded a 12V 25W bulb and connected my ATX SMPS Tester and applied power. I was very glad to see the fan running, the bulb glowing very well and the Tester showing healthy light up! Let us look at the pictures:
Missions accomplished with double satisfaction getting collected to the bag!
This article was prepared for you by Parasuraman Subramanian from India. He is 74 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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Albert van Bemmelen
August 28, 2024 at 2:15 pm
You make fixing smps units always sound so easy as playing guitar which looks easy but requires many years of training! Which you no doubt have! LOL!
Parasuraman S
August 28, 2024 at 4:58 pm
Thanks for the valuable compliments, dear Albert!
Mark
August 28, 2024 at 2:21 pm
Well done Parasuraman for saving these from waste and putting them back into service.
Parasuraman S
August 28, 2024 at 4:59 pm
Many thanks, Mark!
Yogesh Panchal
August 28, 2024 at 6:29 pm
Good job! Sir
Parasuraman S
August 28, 2024 at 9:02 pm
Thanks!
Mark J
August 28, 2024 at 11:55 pm
Parasuraman Subramanian I enjoy working on switch mode power supplies to. Well done on the repairs.
Parasuraman S
August 29, 2024 at 8:04 pm
Yes, it is really challenging and therefore a thrill to work on such SMPS! Many thanks, dear Mark!
PHILIP
August 30, 2024 at 11:40 pm
Thanks Parasuraman for the good report. Your good stock of capacitors is proving to be quite useful. In the second repair you substituted quite a handful of electrolytic capacitors. Lack of even the closest required capacitor replacement that may be hard to come by will make a technician abandon a repair. You know the SMPS and some other sensitive circuits dont like modifications. The other thing is, I always wonder why you never mind to replace the ceramic capacitors, and how do you single out failed ceramic capacitors. Also how do you replace a ceramic capacitor knowing that some of them are never rated. May I request you that, one of this fine days explain how a modified crt tv can be used as an oscilloscope, I badly want one for use. New ones are costly, though very ideal. Also making use of a few crt tvs to make oscilloscopes will rescued some crt tvs on their way to the dumpsite in some places, and the environmental pollution degree caused by e-waste will have been lessened, even if marginally.
Parasuraman S
September 1, 2024 at 9:21 am
Hi, Philip! Nice to see a good feedback. Shall try to reply one by one: 1) Fixed capacitors do have markings, but could get unreadable due to dust formation. I clean it gently using a spectacle cleaning cloth and IPA. If quite unreadable, I check its value and decide replacement depending on the usage there. 2) There are a lot of videos and guidance available in the web for converting CRT Tubes to oscilloscope. Please search. Here is one : https://www.youtube.com/watch?v=vHvbCWVtPzY