Lenovo/LiteOn PS-5281-01VF PSU: DEAD [FIXED] - Page 1
Forum section: electronics / repair

author: Inflex
author_rank: Regular Contributor
timestamp: January 10, 2017, 07:53:59 am
content: Thought I'd just put this one up on the forum so that other people can find it if they encounter a similar problem in the future.Device: Lenovo/LiteON PS-5281-01VF (different to the -7VWN) Slim form factor 250~280W PSUFault:No power up, nothing, tester doesn't power up either+5VSB (Purple) only showing 0.9VWork done:1) Opened up unit, noticed a couple of the main DC output caps were leaky, replaced those; Still won't start2) Diode check on 5VSB+ secondary side parts all comes back good2) Used hot air station at 220'C and started warming up parts, located faulty area, turns out area on primary side of smaller transformer is sensitive, replaced 22uF 50V electrolyte (no visible defects) and finally the PSU is working again.Sounds simple looking back, but that took me all too long to work out. Sometimes I wonder if it isn't easier to start with tests like this before anything else. Almost guaranteed though no matter which method you start with, it will be the wrong oneAs a bonus, the fan was turning slowly, and it was a 90mm unit (not 80mm) so I threw that in to the ultrasonic cleaner and relubricated it, good as gold again.Normally I'd not bother repairing PSUs, but this one I couldn't get a suitable replacement quick enough at a sane price in the country... so repairing it was.

author: Inflex
author_rank: Regular Contributor
timestamp: January 10, 2017, 12:43:10 pm
content: I forgot to make note, the purpose of the 22uF 50V cap looks to be to provide Vcc for a controller chip such as Infineon ICE3B0365J (simple diode-cap rectifier/low-pass) and most of the controller chips have low voltage lockout; as such, with the weaker cap the LV lockout would have likely remained.

author: vasekpetr1
author_rank: Newbie
timestamp: September 29, 2018, 11:12:14 am
content: Thank you very much, helped.

author: princeofabyss
author_rank: Newbie
timestamp: November 29, 2018, 03:40:56 am
content: I hope someone can enlighten me about this particular PSU that died yesterday...Similar case with the OP's, a couple of leaky caps, but also two blown-up resistors, R111 and R401 on the PCB. Problem is obvious, I can't know what values they were before they blew-up.So 2 questions:1. To eveyone: Would you guys be able to find a service manual for me of this particular model, so that I can look the two parts up?2. To OP - Inflex: Would it be easy to check in your PSU, if you still have it, or if you have taken any other photos of it when you originally opened this topic, to try and find the Ohm/Watt values of R111 and R401? They are located just below the 3 transistors with the big heatsink.I'm also attaching a clear picture of my blown-up parts for you to see.Thanks a lot in advance guys!PS: Because of the file attachment limitations, the attached image is somewhat small. If you need to see it in full size, I also uploaded it here:https://imgur.com/a/x4Q9HBl

author: Inflex
author_rank: Regular Contributor
timestamp: December 14, 2018, 03:32:09 am
content: Sorry, can't help you with that one. No idea.

author: cvanc
author_rank: Frequent Contributor
timestamp: December 16, 2018, 04:13:09 pm
content: Quote from: Inflex on January 10, 2017, 07:53:59 amLOL truer words were never spoken!

author: Behemot
author_rank: Contributor
timestamp: March 24, 2021, 06:29:28 pm
content: They are actually not resistors, but fuses, F10A. Likely should have been fusible resistors (something like 0,01 ohm) in that place.In my case, all caps are quality japanese and fine, fuses also intact. I do get +5 V SB and PWR On (also 5V) signal, but putting it low does nothing, the main supply does not start