[FIXED]-SMPS TV3206 REPAIR( TV POWER SUPPLY) - Page 1
Forum section: electronics / repair

author: kgavionics
author_rank: Regular Contributor
timestamp: February 09, 2017, 06:47:27 pm
content: Hi guysi'm trying to fix a 32 inch Lcd Haier TV and i'm stuck,because mainly, i no longer have my oscilloscope.First, all the capacitors looks good, no bulged caps found.I took some mesurement and i missing +12V on 2pins and i missing +24V and the CON1 ( see picture)im suspectiong the mosfets, but i'm not quite sure.can someone help me with this problem please?

author: RayRay
author_rank: Frequent Contributor
timestamp: February 09, 2017, 07:27:59 pm
content: When it comes to repairing electronics, looks can definitely be deceiving!Just because the capacitors physically look okay, it doesn't mean they're all good!I suggest you get a good ESR & Capacitance meter to properly test those.You have multiple options in that regards, such as:1. Getting a combined ESR & Capacitance meter (such as the Peak ESR70)2. Getting a standalone ESR meter (such as the MESR-100) if you already have a capacitance meter (or a multimeter that has that function with good enough ranges)3. Getting both in separate units (like for example, using UNI-T UT601 for capacitance, and MESR-100 for ESR)Generally speaking, you can measure both Capacitance and ESR with the capacitors in circuit just fine (only if they're not connected in parallel!)If connected in parallel, you'd have to remove the specific capacitor/s from the circuit for testing.This can be easily checked by measuring the resistance between nearby capacitors (if you get any at all, from one capacitor to the other, then it means they're in parallel!), before measuring a capacitor, use pliers (or a screwdriver) to short the leads just to make sure they're discharged.This technique work fine for low voltage capacitors, but is risky for high voltage ones (which would require a resistor with wires attached, or a special capacitor discharge tool) but set all that aside, if you don't wanna invest the money in those meters, then you could simply replace all capacitors and see how that goes. This option would actually be cheaper. Just make sure you get low ESR caps, preferably of reputable brands (Such as Rubycon/Nichicon/Panasonic) this would of course require having a good soldering iron (or station) and good soldering skills.The general rule of the thumb is (for capacitor replacement) is to get capacitors that have the same capacitance rating, and the same (or higher) voltage. I.E a 1000UF 25V cap can be replaced with a 1000UF 35V for example.Apart from the capacitors, you should test the resistors (just use a resistor color code calculator to get their values and put your meter on the correct resistance range if it's not an auto-ranging one), I use these on a regular basis:http://www.digikey.ca/en/resources/conversion-calculators/conversion-calculator-resistor-color-code-4-bandhttps://www.easycalculation.com/physics/electromagnetism/3band-resistor-color-code.phpIf a specific resistor doesn't give you the right value, then you'd have to desolder it, remove it from the circuit, and re-test.Also test the diodes (pretty much all modern multimeters have a diode testing function for that purpose)To give you a basic rundown, diodes (unlike resistors) do have polarity, so you need to make sure you get that part right.The negative side is usually indicated by a gray circle (on a standard black diode) or a black circle (on a zener diode)To put it simple, with a standard diode, you should only be getting a reading in one direction (if you reverse the polarity, you're not suppose to get a reading at all, if you do get a reading, then that would mean the particular diode is shorted and needs to be replaced!)The same however doesn't fully apply with zener diodes. A healthy zener diode (when out of the circuit) would too give you a reading only in one direction, when in the circuit however, it can give you a reading in both directions (if certain conditions are met, depending on the other components) so it can be misleading when testing. If you get a two-way reading (in both directions) from a zener diode (while in circuit) then you should definitely remove it and test it out of the circuit (because as I've stated above, it can be misleading!)In summation though, electrolyte capacitors are the least reliable components of any circuit board, so I'd say odds are that that is the issue.But you wouldn't really know for sure until you have things fully tested (or try replacing all caps!)Edit:After further checking, it appears you can actually get an identical replacement board from a number of ebay sellers:http://www.ebay.com/itm/HAIER-L32D1120-POWER-SUPPLY-303C3206063-TV3206-ZC02-01-A-/182373860129?hash=item2a76544321http://www.ebay.com/itm/VIORE-LC32VH70-POWER-BOARD-303C3206063-TV3206-ZC02-01-A-/172424243341?hash=item282549288dhttp://www.ebay.com/itm/Westinghouse-32-VR-3215-303C3206063-LCD-Power-Supply-Board-Unit-/361405389753?hash=item5425709bb9http://www.ebay.com/itm/Westinghouse-Power-Supply-Model-CW40T8GW-TW-70321-S040K-Part-PS1103159AC-/322368330544?hash=item4b0ea65b30So it's up to you, you can either attempt to repair the one you currently have, or just get a direct replacement (which will probably save you some time and frustration!)

author: kgavionics
author_rank: Regular Contributor
timestamp: February 09, 2017, 08:48:34 pm
content: Thanks RayRay for the heads up.I'm gonna try to fix it my self.Right now i'm testing the capacitors out the board, after i'll test the rest of the components.thanks again

author: RayRay
author_rank: Frequent Contributor
timestamp: February 09, 2017, 09:14:43 pm
content: Good luck!Just wondering though, how are you testing the capacitors?And do you have both a capacitance and an ESR meter?In some cases, you can have good capacitance and bad ESR, while in others, it's on the flip side, so you really need to have both in orderto fully test em.

author: Cupcakus
author_rank: Contributor
timestamp: February 10, 2017, 06:47:50 am
content: They sell those cheap component testers on EBay and Amazon, sometimes as a kit, that will test both ESR and Capacitance, everyone should have one. I've repaired a bunch of these TVs and it's always the caps on the low voltage side. Typically only the 5V rail is working.

author: kgavionics
author_rank: Regular Contributor
timestamp: April 09, 2017, 05:53:20 pm
content: hi guysI've replaced all the capacitors on the power supply and i have the same problem, the voltages are the same, nothing changed.What could be the problem? Is the 3.5 V on STBY pin normal? i have checked also the MOSFET's and i have 0V on their Drain's pins.this problem is getting me crazyPlease help!!

author: kgavionics
author_rank: Regular Contributor
timestamp: April 09, 2017, 08:17:33 pm
content: I think i have found the problem.One of the final stage switched mode power rectifier diode is shorted out.It's part number is MBR20200CT, if i test between the pin1 and 2 it gives me a short, but between pin3 and 2 it gives me a voltage drop of 0.29V.

author: kgavionics
author_rank: Regular Contributor
timestamp: April 09, 2017, 11:00:53 pm
content: Problem fixed.the tv is working like a charm.It was the dual diode rectifier (MBR20200CT) , i replaced it with an equivalent one (SF20LC30) .All the old caps were good, so i put them back.thank you guys