Vizio vw37l hdtv10a

[halobender]

I hijacked an older forum hoping someone had a shortcut to help me find what may be wrong with this set. Decided it would be best to just start my own thread and hopefully with your help we can get this tv up and running so I can give it to my grandparents.

Background: TV appears to have taken a surge from the AC coming into the unit. Other than some discoloration on the chassis and slight black discoloration around the AC terminations everything seems to look good appearance wise. No buldged caps, no burnt fuses, no popped resistors, etc.

After plugging the TV in I found that it would not attempt to power up. I checked the main fuse on the ps and it is good. I checked fuses f1 and f2 on the main board and both test fine as well but f2 does not have the 5v input or output that it is supposed to have from the ps.

Any ideas where to start? I have been trying to follow the service manual which listed checking f2 for 5v. Then asked if J1 connector is good. There is no dc voltage present on the J1 connector but the connector appears to be okay. Next step is DC-to-DC. Not sure what this implies. I did test the bridge rectifier and it tests fine. Last step is to check U8 pin 2 for 3.3v, which also has 0v. Of course this makes sense as I don't have any dc present leaving the ps.

[vinceroger69]

Re: Vizio vw37l hdtv10a

[vinceroger69]

Re: Vizio vw37l hdtv10a

in picture 3 can you remove that board and take a picture of the underside of the pcb.

[halobender]

Re: Vizio vw37l hdtv10a

in picture 3 can you remove that board and take a picture of the underside of the pcb.

Yeah that's the PS. The solder joints were okay but I reflowed them just to be sure there wasn't a fine crack. Also the black and red marks were just to show the f1 fuse location.

[vinceroger69]

Re: Vizio vw37l hdtv10a

no not that board the small one with blue and brown wires going from it to the psu it looks like the board the mains lead from wall socket plugs into

[halobender]

Re: Vizio vw37l hdtv10a

no not that board the small one with blue and brown wires going from it to the psu it looks like the board the mains lead from wall socket plugs into

That is that board. The socket from the wall is CN1 at the bottom right.

[vinceroger69]

Re: Vizio vw37l hdtv10a

sorry yes my mistake, picture took ages too load i will have another look at the picture

[vinceroger69]

Re: Vizio vw37l hdtv10a

being really carfull as high voltage can you test the dc voltage across the large capacitor on the primary side remember this is high voltage and dont let probes slip or touch the heat sinks as some can give shocks etc if your not sure dont test.

[halobender]

Re: Vizio vw37l hdtv10a

I tested it the other day. 167v

[vinceroger69]

Re: Vizio vw37l hdtv10a

so on every pin on the secondary side connectors theres no voltage on any pins?

[halobender]

Re: Vizio vw37l hdtv10a

so on every pin on the secondary side connectors theres no voltage on any pins?

I will recheck again but I didn't see any voltage across any of the three connectors.

[vinceroger69]

Re: Vizio vw37l hdtv10a

use the tv chassis as a ground for your meter earth there should be a 5 volts somewhere and someone more experienced will now if this psu uses pfc etc as not sure if 167 volts is correct but im sure that dosnt boost untill the mainboard turns it on.

[halobender]

Re: Vizio vw37l hdtv10a

use the tv chassis as a ground for your meter earth there should be a 5 volts somewhere and someone more experienced will now if this psu uses pfc etc as not sure if 167 volts is correct but im sure that dosnt boost untill the mainboard turns it on.

Pretty sure the 170vdc is correct without the set being on. I am definitely checking my lower voltages to chassis ground but I haven't rechecked yet. I will do so soon and report my findings.

[budm]

Re: Vizio vw37l hdtv10a

Check the PS-ON pin, it should be >2.5VDC when power switch is activated.
If you do not have PS-ON signal from the main board then there will be no >360VDC from the PFC Voltage booster, and also will not have either 12V or the 24VDC.
More likely to be bad LDO Voltage regulator ICs on the main board.

[jetadm123]

Re: Vizio vw37l hdtv10a

Welcome back budm. He mentioned on a different thread that he has no 5V standby output, which means there's something wrong with the power supply standby circuit.

[budm]

Re: Vizio vw37l hdtv10a

Welcome back budm. He mentioned on a different thread that he has no 5V standby output, which means there's something wrong with the power supply standby circuit.

OK, the that IC under the small wing heatsink is the SMPS IC for the standby circuit, there should be startup/running small electrolytics cap/s close by in that section that should be checked or try replacing it or try heating it with the hair dryer, he can run the power supply board by it self without having the cables going to the main board connected, the rectifier for the STBY output should also be checked.

[halobender]

Re: Vizio vw37l hdtv10a

Thanks for the information bud. So disconnect all other boards on the ps and check the SMPS? I checked the rectifier without power and it tested fine, unless there is a secondary one that I have yet to see. Can you describe in better detail what I need to check and in what order? Just to be clear.