Vizio VW37L TV - no 5v standby voltage

[Drail24]

I recently inherited a 2008 model Vizio VW37L. The tv came from a relative who had used it up until "it would not turn on one day". I have basic electronics knowledge and have been able to repair TV's in the past with the basic "blown caps" issues and such. However, this particular problem is out of my realm of knowledge. The search results have yielded a few threads dealing with this issue, but only a few that are specific to this power supply and almost none that have a complete resolution of the problem. Hopefully, with the guidance and help from the members here, I can track down this problem.

So far, I have determined that there is no 5v standby power (also, no lighting of the vizio emblem, and no other response whatsoever). I confirmed this by disconnecting all cables from the PSU, with the exception of the main power cord. A DC voltage check, with the meter grounded to the chassis, yielded no power on any of the "cold side" outputs of the PSU. The main fuse, next to the power cord plug on the PSU, has checked good for continuity. Additionally, measurements across the two legs of the large capacitor on the hot side has shown 167 volts. From other posts, it seems my next step is to check the #1 pin on the SMPS for fluctuating voltage. However, I am unsure of exactly which item this is on the board that I have.

Any insight would be appreciated.

[budm]

Re: Vizio VW37L TV - no 5v standby voltage

Check Fusible resistor R805 TO SEE IF IT STILL SHOWS <1 Ohm, if OK then check D907, if OK then try replacing C903 startup/running cap.
Pictures provided shopjimmy.

[Drail24]

Re: Vizio VW37L TV - no 5v standby voltage

budm,

R805 shows .5-.6 ohms. I have located D907, but I am unsure how to test it. The "D" is for diode, correct? It Is mounted to the heat sink and has 3 legs. What should I be checking for across the legs?

Thanks

[budm]

Re: Vizio VW37L TV - no 5v standby voltage

The two outer legs are connected together, so to look for short, you will put meter in Ohm mode then check the resistance between the middle leg against either one of the two outer legs, then reverse the meter probes and test again and report the readings, make sure to report what the meter is showing as in Ohm, K Ohm, or M Ohm.

[Drail24]

Re: Vizio VW37L TV - no 5v standby voltage

With the Positive probe on the center leg, and the negative on each outer leg, the readings were 8.0 K ohm for each leg.

Reversed, the readings were 0.965K and 0.966K.

[CapLeaker]

Re: Vizio VW37L TV - no 5v standby voltage

Replace that startup running cap.

[Drail24]

Re: Vizio VW37L TV - no 5v standby voltage

Ok. It will take me a couple of days to get a cap. I will replace that and then report back.

[CapLeaker]

Re: Vizio VW37L TV - no 5v standby voltage

If you order that, I'd be ordering that MIP IC as well.

[Drail24]

Re: Vizio VW37L TV - no 5v standby voltage

Capleaker,

Yes, I will have to order it... no local supply stores near me.

I am not familiar with the MIP. Where on the board is it located, or rather what is its function?

Thanks

[CapLeaker]

Re: Vizio VW37L TV - no 5v standby voltage

Capleaker,

Yes, I will have to order it... no local supply stores near me.

I am not familiar with the MIP. Where on the board is it located, or rather what is its function?

Thanks

Sorry, that MIP IC got into the wrong thread. However check IC900. I can't tell what's written on it on my tablet.

[Drail24]

Re: Vizio VW37L TV - no 5v standby voltage

The markings on IC 900 are: 2A07905 and 5531. A search of 5531 comes up as possibly being a Fuji chip? I found a few different data sheets for the 5531, but am still unsure of exactly what I should be checking for on it. Also, should the start-up cap be replaced before checking the IC?

[budm]

Re: Vizio VW37L TV - no 5v standby voltage

Just try replacing the start up cap first since it is simple enough.

[CapLeaker]

Re: Vizio VW37L TV - no 5v standby voltage

maybe an FA5531

[budm]

Re: Vizio VW37L TV - no 5v standby voltage

Can we get the DCV readings of all the pins against the GND pin 4?
BTW, the app notes circuit is probably real close to what you have on your board.

[Drail24]

Re: Vizio VW37L TV - no 5v standby voltage

Ok, those are the schematics I found as well.. the FA5331. I was confused by the fact that the block diagram only shows 7 pins, when there are 8 legs on the chip. Which is pin #1, #4, etc? Did I overlook something in the spec sheet that determines orientation? When looking at other similar chipsets, they always seem to have a "dot" or marking referencing pin #1.

From reading other threads, pin #4 should be ground.. which is tied to the negative leg of the large capacitor on the hot side. Would it be as simple as doing a continuity test between the negative leg of the cap and each of the pins on the chip to determine which is the ground leg?

[vinceroger69]

Re: Vizio VW37L TV - no 5v standby voltage

pin 7 although on the chip is probably not used or connected to anything in the above pdf it does show the pin layout on page two if your stuck you will have to post a clear picture of the ic on your board and we can point out pin one etc.

[cyberhack]

Re: Vizio VW37L TV - no 5v standby voltage

Looking at the first picture the caps in the cover look bad

[Drail24]

Re: Vizio VW37L TV - no 5v standby voltage

I will post a better picture of the IC on my board when I get home this evening, as I am still unsure as to which is pin#1. Out of the 4 corners of the chip, only 2 can possibly be #1, but which one? It will depend on which way the chip is oriented, or which way you are looking at the chip, unless I am still missing something.. which is entirely possible.

[Drail24]

Re: Vizio VW37L TV - no 5v standby voltage

cyberhack,

The ones under the largest heat sink at the top of the pic? I will inspect those closer this evening.

Thanks

[cyberhack]

Re: Vizio VW37L TV - no 5v standby voltage

Yes very common fault with this type of power supply