Vizio VW37L HDTV20A Power supply No Standby Voltage

[kevinm34232]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

If you're checking for the volatge at the Power IC you should be using the hot ground though, negative leg of main filter cap..

[Worminizer]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

c213 is a 68uf 25v cap, which is tied directly to pin 1, there is another cap right next to it (c208) a 47uf 50v, which is not directly tied to pin 1, but here are its measurements across both legs. .01vdc. I feel confident that it is not the startup cap.

[Worminizer]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

ahh, ok, let me repost those using the neg leg of the main filter cap. That is the giant one correct?

1 9-10vdc fluctuating
2 0vdc
3 0vdc
4 .01-.05vdc fluctuating
5 0vdc
6 .10-.50vdc fluctuating
7 0.00-0.05vdc fluctuating
8 160-164vdc fluctuating

[tom66]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

My error. From the 8 pins, I thought you were testing the output pins.

What is the part # on that 8 pin IC? You may need to use a jeweler's loupe to see it or a good magnifying glass.

[Worminizer]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

EA1532A
7H1W112
Hn67361

Thats everything printed on the ic.

[tom66]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

OK this is your chip:
https://cdn.badcaps-static.com/pdfs/...db19a495c5.pdf

Vcc must be at least 10.3V to start (typically 11V, and could be as high as 11.7V.) Since it's measuring only 9-10V, this is where the problem is. I'd suggest checking the output diodes for shorts. If there are none, replace the startup cap.

[Worminizer]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

I checked it again at pin one, and its going as high as 10.696, but it is fluctuating. I took a min-max and attached a photo. That looks high enough to start, but should it fluctuate like that?

[retiredcaps]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

I checked it again at pin one, and its going as high as 10.696, but it is fluctuating. I took a min-max and attached a photo. That looks high enough to start, but should it fluctuate like that?

1) Way back in post 7, I already posted the link to the SMPS IC. In that diagram, pin 1 is VCC and pin 2 is your GND. That GND is the same as the big capacitor negative leg ground.

2) A fluctuating voltage suggests one of the following

a) the startup cap, c213, is bad (the small ones rarely bloat)
b) the SMPS IC is bad
c) there is something shorted on the secondary output side (like a diode)

3) The SMPS IC needs stable DC voltage in order to work properly.

4) One retiredcaps' bonus point awarded for a picture of your Fluke 289 and an extra point for showing min/max functionality

The startup cap is the easiest thing to change first.

[budm]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

I would replaced those two small caps in the primary side any way, they are cheap and easy to do just to verify they are not causing the problem.
You can also run the power supply without have the connectors on the secondary side connected for now since we are trying to fix the 5V standby only for now.

[Worminizer]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

Ok, guys, I will probably be a while. I flipped the board over while it was still connected and arced it. It fried the power strip, and blew the main fuse. I've replaced the fuse, and it keeps blowing. I have to figure out what I destroyed now, before I can continue. I have a hard short between the two ac feed legs.

[retiredcaps]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

I flipped the board over while it was still connected and arced it.

Too bad. If you were lucky, it might have been a "simple" startup cap that was your initial problem.

I have to figure out what I destroyed now, before I can continue.

Check your bridge rectifier and power mosfet to see if they are shorted.

[budm]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

Replacement from Shopjimmy is $59 with free shipping:
http://www.shopjimmy.com/fsp-fsp201-...wer-supply.htm
You may have shorted bridge. Mosfet, etc. So you may want to think about the pro and con of fixing the new problem plus the old 5v power supply problem. May be you can do that later on as a learning experience.

[Worminizer]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

meh, I'm not really doing this to save money. I'd have to fix it pretty quickly to make it cost effective to try and fix on component level. I do it to learn. If I get to a point where I get super frustrated, and just can't move forward, I will buy the board.

[Worminizer]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

I found three things I need to replace before I continue. The bridge rectifier is shorted between 3 of the 4 pins. Both chokes look terrible, though only one measured shorted. The one on the right has both phases wrapped together and the insulation melted, causing a short. The one on the left doesn't read as short, but thats only because the phases don't come into any contact with each other. The insulation is badly melted on that one too, therefore causing each side of the windings to short in line, thus causing less windings. The bridge rectifier is a US8K 80R. What part number would it be on digikey? I have no idea how to identify the chokes. If someone could point me in the right direction on digikey as to what I need to order, I would be forever grateful. I have a hard time differentiating between their vast inventory.

Thanks,

[retiredcaps]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

The bridge rectifier is a US8K 80R. What part number would it be on digikey? I have no idea how to identify the chokes.

I'm no expert on inductors, but from the little that I do know, if you measure them with a multimeter, it should read like a short. In 2+ years of participation, I don't think I recall an inductor going bad. We have a lot of shorted rectifiers and power mosfets from people doing an "oops".

Rectifier can be found via

http://www.findchips.com/avail?part=us8k

which leads to mouser. Digikey has no stock.

While you are ordering the rectifier, get a startup cap and the other little cap. Get Panasonic FC brand for both.

[budm]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

Those are common mode choke line filter with very low DC resistance, it looks like just poorly applied varnish. They have to be low resistance, otherwise you will have too much voltage drop on them. I would take out the bridge rectifier out and test them out off the circuit since shorted MOSFET will make the bridge read shorted also.

[retiredcaps]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

I would take out the bridge rectifier out and test them out off the circuit since shorted MOSFET will make the bridge read shorted also.

Yes, I totally forgot to mention that. In circuit readings should be verified out of circuit by desoldering the component in question.

[Worminizer]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

I forgot to mention that I already did pull them out. The bridge rectifier should in diode mode read as bridged diodes should it not? It looked good from the first pin to all the other pins(short in one direction only). when I tested from 2-3, 2-4, 3-4, they all showed short in both directions. Is that normal? I pulled the bridge rectifier out and still had short on my feed. I then pulled the inductor on the right, and the short went away on both sides. I tested the inductor out of circuit and all 4 leads are hard shorted.
I only assume that the left one did the same thing, because the right one did. It doesn't show short across the circuit, but it can't, the coils are isolated from each other. However, the coils can be shortened(short circuited),on the same conductor, and without some sort of ring counter, I won't know. I'm just afraid, that it is acting simply as a jumper now.

By the way, these faults were all caused by me flipping the board over and arcing it on a metal housing while it was still plugged in on the bench. Complete goof up, I know, but not your normal tv problem none the same. Sorry about forgetting to tell you, but yes, I did isolate and test the components out of circuit. The inductor at least is bad, and I would think those readings on the bridge rectifier are no good. It's essentially no more than a single diode now.

[budm]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

What resistance do you get when you measure on the two legs of the large cap, make sure the cap is fully discharged. I still suspect shorted MOSFETs, One is for the PFC, one for the 12/24V transformer..

[Worminizer]

Re: Vizio VW37L HDTV20A Power supply No Standby Voltage

250k ohms declining.