Misadventures in Electronics #2: Can I repair a TV that won't turn on? Vizio M552i-B2 / DPS-167DP-1

My attempt to repair a TV using the following parts:
LD7913JGM6 integrated circuit
SR3100 Schottky rectifier diode
1N4732A 4.7V Zener diode
4.7R 1/2-watt wire-wound fuse resistor
#diyelectronics #repair #technology

[@Karen-bj7lc]

Enjoyed watching. Even though there was not a successful outcome, the process looked enjoyably engaging.

[@panagiotismavrommatis8917]

I had a look on the datasheet of LD7913J. The startup voltage to charge the capacitor will come from the primary side of the main transformer coil, where one side is connected to the bridge rectifier. The other side is connected to the Drain of the chip and there, internally, it has a current source(1mA) that will charge this capacitor via its VCC pin. So this capacitor should be charged like this according to the datasheet. It is possible that there is an SMD small value resistor between VCC and capacitor that is burned during the short. Check around the chip and the capacitor for SMD resistors. There is also a very strong possibility that during the short the capacitor took the rectified mains voltage and blew open, that's why is not charging. Just some thoughts 😉

[@grahamhall2662]

Just spent three weeks on similar journey with a solder station. Hacking, modding, swearing, throwing bits everywhere! Done works now, should really have been in the trash. Still don't know why it failed but think the thermocouple in the iron broke so everything got really hot and several components just expired plus hairline cracks in the tracks, fun.😀

[@kingforaday8725]

Now this is how my repair jobs usually turn out!!! ☺

[@Conservator.]

It’s so much more satisfying to fix something on the component level instead of just swapping a board. I really like that you take us with you and explain your considerations during the attempted repair. It’s almost like I hear myself btw. 😁 16:33 Did you first add a bit of leaded solder? That would lower the melting point and make the desoldering a bit easier.

[@picocosm]

I did not try adding leaded solder - that would've been a good idea! Very much agreed on component-level fixes!

[@edwardneuman6061]

I had a LG display that wouldn't turn on. I opened it up and noticed that the electrolytic capacitors is the ps section were bulging so I replaced them with higher quality caps and that did the trick. Its still working years later.

[@picocosm]

Nice! Things are certainly easier when all the problems can be identified from inspection! Wish I'd been so lucky.

[@wisher21uk]

Hi did you check the main input fuse, bridge rectifier, check all mosfets, thanks I have subscribed 😊

[@picocosm]

Welcome to the party! I did check the main fuse and rectifier although I didn't show it in the video. Not entirely convinced the MOSFETs are involved in the charging of that capacitor that seems to be at the center of my problems but maybe I'll desolder the heat sinks and give it a try. Thanks for the suggestion!

[@wisher21uk]

@@picocosmThank you! I’d give it a try, also check the smaller components around the chip you replaced as if a ceramic cap or transistor has failed that will cause the problem 😊

[@frankpitochelli6786]

I would've ESR'd some of those electrolytics, those shottky diodes can be bad actors... I WAS in the TV Repair bizz for almost 40 yrs.....they made tvs throwaways about 10 yrs ago, but, I'm thinking the manufacturers might be getting back to high end electronics... Can't see how they make money selling tvs so cheaply. We'll see what the next few yrs brings. Good video.!

[@picocosm]

Nice! My hat's off to anyone who can actually turn a profit fixing these things. I lost count of how many hours I put into this, but even at minimum wage I think I would've exceeded the cost of a whole new TV. I don't have an ESR meter but maybe that should be next on my list.

[@aiastelamonian6868]

My vizio wouldn''t turn on either. After inspecting the powersupply board sure enough I noticed the ic901 had part of it's epoxy shell missing/blown off. Shipping it for repair since I have no experience in repairing. I'm assuming this board is obsolete since it's out of stock everywhere I've looked.

[@picocosm]

Good call - fixing this thing is harder than it looks! Hope the pros can do a better job than I did!

[@fourhorsemen5]

Is there an LED that lights up on the front of the tv when you plug it in? If not check main fuse and also need to check main MOSFET or MOSFFETs and also double check full wave rectifier. If LED does come on when plugged in does it go out or change color when ON/OFF button is pressed. Try to use buttons as opposed to remote. If changes color most likely Power Supply Board could be backlight LEDs.

[@picocosm]

No light is coming on and I did try the power button on the TV. I also checked the main fuse and the rectifier but didn't show those parts in the video - both seem to be fine. I wasn't really sure what to do with the MOSFETs other than confirm reasonably high resistance been the pins. I'm not entirely convinced the MOSFETs are actually involved in charging that capacitor that seems to be at the center of my problems. Think I should desolder the MOSFETs and have a proper look at them? I've read that a basic test with the meter in diode mode would be: short G to S (transistor off) and put red probe to D and black to S (should show no conductivity), then instead touch red probe to G to turn transistor on and then put red probe back on D (the idea being the gate will have enough capacitance to stay on). I was hoping to avoid desoldering the heat sinks but maybe I'll give it a try.

[@fourhorsemen5]

I'm thinking the MOSFET(s) & Full wave are ok if the main fuse is good. Sounds like you don't have any standby voltage (no led on front of tv). Check for designation on the power board for something like Standby or SB or some abbreviation for 'Standby'. This should be next to the connector that goes from the power board to the main board. Should be maybe 5volts (sometimes 3 volts). If you don't have this voltage there an issue with the power board (trace back to where this 5volt comes from ) or if you do have this voltage probably an issue with the main board.

[@fourhorsemen5]

I think I can see it pin 2 & 3 on CN101 (14pin) '5VSB'

[@picocosm]

Yes, the 5V standby voltage isn't happening. I think that IC that I replaced is responsible for generating it, which is why I was trying to figure out why the capacitor that turns that chip on isn't charging.

[@andrew_koala2974]

Congratulations for being able to write ON / OFF and MOSFET correctly The ZOMBIES (meaning - those that have eyes and cannot see - ears and cannot hear ) will not notice and never learn from it. Neither have they learned that all CORPORATE legal names are always in the ALL CAPS iteration

[@chemscrambler7589]

it looks like you didnt solder the chip in good. you have to use flux and really heat the board up melting the solder. your reflo looked like you was waving a wand not acually doing anything?

[@picocosm]

Yes, waving the heat wand around really didn't work very well. You see me looking at things with tweezers during that process trying to test if the solder was actually melting. Most of the time it wasn't, but after causing a blister to form on the board I have up. It was a final stab in the dark that I didn't have high hopes for going into it. If I knew of a specific joint that was bad then I certainly would've tried to address it more properly.

[@kingforaday8725]

In all honesty unless one repairs these things just for "fun" its generally more economically sound to just buy a new one.

[@rosariodagosto6484]

WHO USES FUSABLE RESISTORS THIS DAYS 😊

[@cotto887]

Why didn't you test the components?

[@picocosm]

I actually did test a number of the components out of circuit but didn't show the entire process in the video.

[@todorkpstov3519]

😂😂😂😂😂

[@gaineredison390]

Are you doing it for fun? It's gonna be more fun if you learn how to test these components with right tools; Resistors, capacitors,Diodes, transistors and voltage on their clutial points.

[@andrew_koala2974]

CORRECTED TITLE Written in correct grammatical legal English Misadventures in Electronics #2: Can I repair a TV that won't turn ON? VIZIO M552i-B2 / something you have yet to learn as your Education system is a total failure Pay attention to the difference and learn to pronounce SOLD ER correctly Practice saying SOLD ( a hundred timed ) It is not difficult.

[@picocosm]

Sorry, mate, but that's the prevailing pronunciation in my country. Best not to watch my videos if it bothers you that much.

[@johnlucier8572]

Too much time talking at the beginning of the video and very slow at that. So with that I left your site. Terrible. Too many videos like this instead of getting to the point.

[@picocosm]

Thanks for unsubscribing - I'm sure you'll find other KZbin channels that better strip things down to the duration of the average bowel movement.

[@andrew_koala2974]

Perhaps these people should proceed from being born - to the end of life DEATH stage - thus getting straight to the point by disregarding everything in between - that would also minimize the duration and number of bowel movements. -- Every book - every movie - every story and every life - has a beginning - a middle and an end. regrettably - not every'one' understands this principle - only desiring instant gratification