Philips TV won't turn on, power supply issues. - Page 1
Forum section: electronics / repair

author: Yamin
author_rank: Frequent Contributor
timestamp: October 27, 2019, 09:21:49 pm
content: Hi guys,I have got a Philips tv which does not turn on. When the AC mains is switched on the relay clicks and it turns back off in 1 second. The fuse is not blown. There is no stand by light either.I tried uploading the schematic pdf here, but it doesn't seem to work so here is the link for the schematichttps://elektrotanya.com/tcl_40-ipl32l-pwg1xg_psu_sch.pdf/download.htmlI couldn't find any bulged capacitors (I have checked most of them with my ESR meter as well) or any dead shorts.However during my test procedure I had a 100W bulb in series with the power supply, there was a buzzing noise coming from IC1 which is L6563. I measured the VCC pin of the IC and it measured somewhere around 30V! (datasheet's stated max value is 22V). I tried measuring voltage at other pins and noticed that when I probed pin 1, the light bulb doesn't glow bright (starts to flicker) and the buzzing stops. I thought it could be a loose connection so I have re soldered the IC. But there is no difference at start up the buzz is still there unless I touch the pin 1 with the probe.On start up the bulb is lit at full brightness and turns off when the relay turns off.I am quite puzzled, I hope you guys could shed some light.Thanks in advance.

author: kosomsk
author_rank: Regular Contributor
timestamp: October 30, 2019, 07:27:04 pm
content: Hi! Show measurements here

author: Yamin
author_rank: Frequent Contributor
timestamp: October 31, 2019, 10:39:58 am
content: Further development, I turned on the power supply manually without the main board connected. Then the voltage measurements are stable and the relay does not turn off. So that leads me to think that there is a short in the main board. Have you got any tips on troubleshooting the main board?I'll put up the model number of that board.

author: PKTKS
author_rank: Super Contributor
timestamp: October 31, 2019, 12:16:14 pm
content: Quote from: Yamin on October 31, 2019, 10:39:58 amGood not all PSUs will soft start without load.That is typical issue with SMPS.Detached mobo can be powered w/external sourcetry using alcohol or thermal image to spot the dead short.Paul

author: kosomsk
author_rank: Regular Contributor
timestamp: October 31, 2019, 03:04:57 pm
content: At first you need check connector to mainboard on short between pins and ground

author: kosomsk
author_rank: Regular Contributor
timestamp: October 31, 2019, 03:08:11 pm
content: Do measurements when psu connected to mb

author: Yamin
author_rank: Frequent Contributor
timestamp: October 31, 2019, 07:02:04 pm
content: Thanks, I shall try. I have attached a picture of the main board showing the model number. Any idea where to get a schematic for it?Once again thanks very much.

author: pepona
author_rank: Contributor
timestamp: October 31, 2019, 07:05:14 pm
content: Hi Yamin, when you connect this smps to the main power, the relay clicks and start the PFC and the 24V source for a moment.Then there is only the 5V power generated with the FSQ510.These TVs have the peculiarity of not turning on the standby LED if you press the button from the TV itself. It is better to use the remote control.A very common fault is that the relay contacts are charred and although you can measure 24V the necessary current is not enough.You must also change CB1: 4.7µF - 450V capacitor that is next to the FSQ510.I hope you understandSorry for my bad EnglishRegardsMarcos.I cant see the model correctly , could you show it in a better way?