Vizio VO47LFHDTV10A - No Backlight

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

Some encouraging progress:

1. On the Slave inverter, I replaced the IC, reinstalled the good MOSFETs, and replaced the two MOSFETs that shorted out.
2. Now half of the backlight works, the side that's driven by the Master inverter.
3. One thing though: one of the transformers on the Master inverter is buzzing... A loose winding, maybe?
4. The backlight side driven by the Slave is still dead, but at least nothing on the Slave inverter has shorted out... So far. *fingers crossed*
5. Is it possible that one or more of the "good" MOSFETs that I reinstalled on the Slave inverter isn't really good, but not shorted, either?

Correction:

It wasn't half of the backlight... I didn't have the room dark enough.

This is what the display looks like now... But I still get that high pitched whine from one of the the Master inverter's transformers.

[budm]

Re: Vizio VO47LFHDTV10A - No Backlight

That is due to only 1 inverter board is working, the lamps are trying to come on but not enough drive Voltage due to only one working inverter board.
It is getting tough for me to do remote troubleshooting at this point.
It may be that the IC is not driving either set of the MOSFETs right now, the inverter has two set of transformer drive circuit. Are you sure it is getting the 24VDC through the fuse?

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

Well, that was short-lived: The backlight died again and the Slave inverter board shows another short (Vin to GND) condition again... Groan.

I suppose it's just a repeat of the previous failure, but it just took a little longer for the Slave to fail this time.

It is getting tough for me to do remote troubleshooting at this point.

I completely understand... I really appreciate all the help and information you've given me so far... Thanks!

It may be that the IC is not driving either set of the MOSFETs right now, the inverter has two set of transformer drive circuit. Are you sure it is getting the 24VDC through the fuse?

The fuses on each inverter board still show to be good... 0 ohms.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

Today:

1. I removed all eight MOSFETs from the Slave inverter board, reconnected the power cable and the flat cable from the Master inverter, but did NOT connect the two-wire connector to the CCFLs.
2. Turned on power and about 3/4 of the blacklight turned on (see photo) and there was no high pitched whine from the transformers on the Master inverter board as from the previous tests.
3. I would've thought the Slave inverter would power half of the backlight, but this is clearly not the case... Why? What is the main function of the Slave inverter?

[budm]

Re: Vizio VO47LFHDTV10A - No Backlight

Here is the explanation about various backlights driving methods, similar topology as used in your TV.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

Well, it seems pretty obvious that there's something wrong with the Slave inverter board, but I can't figure out what... I've replaced the IC and the MOSFETs (multiple times) and the board still shorts out not long after power up.

Could it be one or both of the transformers? They don't show a short condition on my DMM.

Could it be the support circuitry (surface mount diodes, transistors, caps, resistors)?

I'm nearly resigned to the point that I'll have to buy a replacement Slave inverter board... If there's one available for purchase... At a reasonable price.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

Success!

I made one final replacement of the IC and MOSFETs on the Slave inverter board using a parts kit from ShopJimmy.com and it seems to have fixed the problem...

The only thing I can speculate is that the other ICs and MOSFETs that I purchased from eBay were bad/defective... I'm going break-in/burn-in the TV just to make sure that this repair isn't temporary...

[budm]

Re: Vizio VO47LFHDTV10A - No Backlight

Great job!
It is hard to tell if the parts from China are real or good or not and that can cause lots of headache, but I am glad you did not give up. I do trust shopjimmy and I bought lots of parts and boards from them and have very little problem from them.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

Great job!
It is hard to tell if the parts from China are real or good or not and that can cause lots of headache, but I am glad you did not give up. I do trust shopjimmy and I bought lots of parts and boards from them and have very little problem from them.

Thanks! And thanks for your support!

Now I've got to figure out what's wrong with my nephew's 24" LCD computer monitor.....

[nomoresonys]

Re: Vizio VO47LFHDTV10A - No Backlight

Thanks dskall, I'm not very familiar with motherboards, so I can't really check the other components without instructions to be honest, but I can re solder that coil and possibly other things in that area. What other than that coil would be important to re solder?

http://www.shopjimmy.com/delta-dps-3...wer-supply.htm usually 180 day warranty.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

Slight hiccup:

I was using the TV on a regular basis to burn it in and the backlight went out again.

This time, the Master inverter board failed: it showed a short between Vin (24V) and GND. I removed the IC and MOSFETs and replaced them with the ones from ShopJimmy and now everything is good again.

Again, I'd have to speculate that the previous IC and MOSFETs that I bought and installed from eBay were of questionable quality... Let's hope the parts I bought from ShopJimmy are much more robust.

[budm]

Re: Vizio VO47LFHDTV10A - No Backlight

You are becoming expert at replacing the SMD IC now, I do hope the parts from SJ will hold up.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

You are becoming expert at replacing the SMD IC now, I do hope the parts from SJ will hold up.

I've done more than my share of removing and installing electronic components at work, so it's second nature to me... Having the right tools available helps a lot.

[nomoresonys]

Re: Vizio VO47LFHDTV10A - No Backlight

Slight hiccup:

I was using the TV on a regular basis to burn it in and the backlight went out again.

This time, the Master inverter board failed: it showed a short between Vin (24V) and GND. I removed the IC and MOSFETs and replaced them with the ones from ShopJimmy and now everything is good again.

Again, I'd have to speculate that the previous IC and MOSFETs that I bought and installed from eBay were of questionable quality... Let's hope the parts I bought from ShopJimmy are much more robust.

Seems like they are selling defective parts, care to mention the seller? might help others avoid wasting money and time buying their faulty components.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

Seems like they are selling defective parts, care to mention the seller? might help others avoid wasting money and time buying their faulty components.

This is the eBay seller: https://www.ebay.com/usr/giorgio11185

[nomoresonys]

Re: Vizio VO47LFHDTV10A - No Backlight

This is the eBay seller: https://www.ebay.com/usr/giorgio11185

Thanks, looked at some of their negative feedback, not too good, if I could find a way to make a note to myself on ebay to avoid, I sure would.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

Well, that didn't last a week... Different problem:

Now I get a display, but it only lasts for a couple of seconds and the screen goes blank... I can repeat this every time I turn on the TV.

I'll have to do some poking around, but I suspect it's the power supply... The Asus computer monitor that I was planning to work on has the same issue.

Groan.

[vinceroger69]

Re: Vizio VO47LFHDTV10A - No Backlight

if its the 2 seconds to black fault a lot of the time we see its either a bad transformer or failed ccfl tube

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

if its the 2 seconds to black fault a lot of the time we see its either a bad transformer or failed ccfl tube

Would a single failed tube cause the entire screen to go black?

I would've thought a single failed tube would show up as a black streak across the screen.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

if its the 2 seconds to black fault a lot of the time we see its either a bad transformer or failed ccfl tube

Is there a way to determine if the transformer is bad?

If it is the transformer, this could be a deal breaker since trying to find a sole sourced/proprietary replacement transformer will be nearly impossible.