UV sterilizer power - Page 1
Forum section: electronics / repair

author: esheng
author_rank: Newbie
timestamp: December 29, 2014, 05:11:27 pm
content: Hi, i got a made in china UV sterilizer and it was working fine till a recent power trip in my place... after which it has stopped working...Took it a part and found that the high frequency transformer is not functioning but am unsure if i am right on that.The transformer has 4 input (2 power, 2 gnd) and 2 output (12v and gnd), i have measured the output coil is working at 0.1ohms but when connected.. then is no voltage across as such the control circuit has to power to function...So would like to ask for help in checking of high freq transformer...Thanks.. it needed, i can post the model and pic of what have been checked..

author: tautech
author_rank: Super Contributor
timestamp: December 29, 2014, 07:25:23 pm
content: Welcome to the forum.Yes photos required.Likely it will have a SMPS and the first step will be to indentify the controller and reverse engineer the schematic.Hopefully then a faulty component can be identified and replaced.Have you the required tools, DMM, Iron, etc

author: esheng
author_rank: Newbie
timestamp: January 04, 2015, 03:57:19 am
content: Hi have found the SMPS controller for this and it is LN1F08 which output 330V from 240V to supply the UV light. Then it uses a tranfomer to bring down to 12v for the fan to dry the stuffs and supplying this 12v to a 5v regulator to supply the controller board.

author: esheng
author_rank: Newbie
timestamp: January 04, 2015, 04:01:51 am
content: Have probe the output of the SMPS controller and 330v is produced with 2pcs 4.7uf cap as reservoir... but there is not output from the transformer for the 12v.. tested the leads on the 12v from the transformer and reading at 0.2ohms. The 2 cores on the other 330v is 5ohms and gnd is 1.1ohms

author: esheng
author_rank: Newbie
timestamp: January 04, 2015, 04:03:36 am
content: The actual board photo

author: SeanB
author_rank: Super Contributor
timestamp: January 04, 2015, 05:27:28 am
content: Change EC3, R2, R3 and R4, and if it still does not work then the IC bottom left is faulty and needs to be replaced.

author: esheng
author_rank: Newbie
timestamp: January 05, 2015, 04:55:43 pm
content: Ic bottom left? Means the IC HV side? Cause i mean there and got 330v

author: SeanB
author_rank: Super Contributor
timestamp: January 05, 2015, 05:06:45 pm
content: That is correct. That is the switch and driver control. If there is no power to the chip because the capacitor or the resistors are open circuit then it does nothing. Otherwise the IC has failed along with the capacitor.

author: esheng
author_rank: Newbie
timestamp: January 10, 2015, 07:14:47 pm
content: Hi seanB, thank you very much on the enlightenment given.. it was indeed R3 resistor gone that cause the SMPS controller to stop working.... replace that 1M resistor and working again.. thank you very very much for the sharing of knowledge...

author: SeanB
author_rank: Super Contributor
timestamp: January 11, 2015, 08:56:04 am
content: I always distrust 0.25W resistors with more than 100V across them, they will all eventually go open circuit from voltage stress, unless you are using high voltage units.

author: esheng
author_rank: Newbie
timestamp: January 11, 2015, 04:38:15 pm
content: I still used a 0.25w resistor to replace and prove the error.. will be getting bigger wattage resistor to ensure the lifehood of the circuit...

author: esheng
author_rank: Newbie
timestamp: January 04, 2017, 04:13:14 pm
content: Quote from: esheng on January 11, 2015, 04:38:15 pmHi all, the sterilizer broken down now and truly out if wizes to fix it.. The switch IC giving me 150VDC output but does not get thru to the 5V side therefore not able power up the IC.. Any suggestion when to start? Checked that the switching IC support resistor are find and within specs.. Thanks in advanceSent from my LG-H961N using Tapatalk