Vizio DPS-167DP-1 failure

[linksys1127]

Thank you for the data sheet you provided! When I get a chance to return to this project I’ll update what I find. Right now I feel like I’m chasing my tail on it! Keeps leading me back to the PWM IC being faulty. When I ordered them they came in a pack of five. I replaced it with another. Same result! Need to walk away for a bit for a fresh prospective! Have other projects that need attention. Thanks again for your update!

[Nr4ps]

I never figured this out. I don't think it can be the replacement LD7913 that I installed because, according to the datasheet that chip doesn't even turn on until the brownout protection pin is above a certain voltage - and the capacitor on that pin won't charge.

[linksys1127]

I’m struggling with this board as well. Initially I had the same defective parts. Replaced them and still nothing. I have scoured my board to find the defect. I’ve found nothing out of range. It’s a real head scratcher! The only thing I can think of is a defective LD7913. Did you get yours working? What did you find?

[Nr4ps]

I have run across a situation where one of the zener diodes was leaking and you couldn't tell by testing with multimeter, maybe replace those?

I don't know if this addresses that thought correctly, but to a quick test in reverse bias the four zeners in that cluster that I didn't replace seem to break down at about the right voltage:

Zd900 6.1V (labeled 6V2)
Zd902 12.7V (labeled 13B)
Zd904 15.9v (labeled 16B)
Zd907 24V (labeled 24B)

[Nr4ps]

The kit on ebay includes the same four parts that I already replaced. I've been looking for a bad solder joint but not finding anything. Everything I resoldered has continuity to where it seems like it should. CN202 looks fine, and I think that connector is just for getting power to the backlight anyway. Wish I understood more how this thing was supposed to work. I was hoping to avoid buying a whole new board, but maybe I'm just being stubborn at this point.

[nomoresonys]

Another thing to check is CN202 connector, make sure all the solders are good.

[nomoresonys]

Check the description on this kit, might give an extra clue: https://www.ebay.com/itm/11448308479...sAAOSwlc1fllAn

[nomoresonys]

There's the ebay page, most kits show the same parts, there's a board there for 50 bucks: https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15

[nomoresonys]

Guess I don't know, I have run across a situation where one of the zener diodes was leaking and you couldn't tell by testing with multimeter, maybe replace those? I don't think I would go with 200 volts on that replacement cap, that seems like quite a stretch from 50 but DO NOT go below 50, maybe recheck your work, many time a solder will look good but not be. I can't even remember how these things work, bad memory. I'll brush up on it if I get time.

[Nr4ps]

C910 measures 64 uF in-circuit. I imagine that means there's another capacitance in parallel with it somewhere and that's not all due to that tiny ceramic cap. But it's not shorted. Is that good enough or shall I desolder it?

R915 is also one of the components I originally replaced. It measures 4.7 ohms.

For C904B I found a 15uF 200V capacitor that I put in, and it still doesn't charge. This is with IC901 installed again. (Original measures good at 10.5 uF out of circuit, by the way.)

Thanks for your ongoing suggestions. I'm a little impressed you haven't given up on me yet.

[Nr4ps]

ZD909 and D950B were two of the components that were originally blown and I had to replace. Replacements were tested out of circuit. I also measured R907 A and B at about 2 ohms in circuit.

IC901 datasheet attached.

I'll get back to you on C910 and trying to find a closer replacement for C904B.

[nomoresonys]

Be sure to check ZD909 and D950B, ZD 909 will need to be checked out of circuit, maybe also check C910, check R915, also check R907 A and B on bottom of board by IC901, R907 A and B should probably be about 2 ohms.

[nomoresonys]

So grab a 10 to 50 uf 50 volt cap and put in there, you can find them in a lot of old junk non-working electronics if you don't have one at hand, grab the datasheet for IC901 and post it here.

[Nr4ps]

I tried 100 uF 100V and still nothing.

[lotas]

0.47 µF 50 V is very small, set 10, 22, 33, 47 µF 50 V.

[Nr4ps]

Original was 10uF 50V. I replaced with 0.47uF 50V (closest I had). Still doesn't charge. I think I'm going to have to figure out more about how this thing is supposed to work. 120 VAC comes in and gets converted to 170 VDC at BD1, labeled in photo. Right now, pins 2 and 3 of T901 sit at 170VDC relative to that same negative post. I guess an AC component is supposed to ride on top of that to energize the transformer, but I'm not getting any.

[nomoresonys]

If that cap isn't doing anything it might be bad, do you have a spare to try.

[Nr4ps]

C904B doesn't charge with IC901 removed either.

[Nr4ps]

Yeah, I was thinking about that... IC901 came from eBay because it's hard to find anywhere else, and it's the one part of the four that I don't know of any way to test. Maybe if I remove it from the board again I can at least see if that somehow allows C904B to charge to a couple volts such that IC901 would start if it were present.

[nomoresonys]

Where did you get your parts, I suppose you could have received a bad IC901, good practice to test the parts that you can before installation.