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**PlainBill** · 01-14-2011, 08:26 PM

Re: VIZIO VO42L No picture, No Sound

The PS_ON voltage is normally about 3 volts. 2.67V is well within the range for 'about 3 volts'.

There are a limited number of tests that can be done with the equipment you have. I'll try to repeat this later, but remember there are two grounds in the power supply. The HOT ground extends from the bridge rectifier to the SMPS transformer. The cold ground is on the AC input and the DC output. And remember that the main filter cap can have up to 400 volts on it if the power supply has a PFC front end (most do).

Good pictures of the top and bottom of the power supply are essential. Note the links in my signature for information on what we are looking for.

PlainBill

**CrappyCap** · 01-15-2011, 03:39 AM

Re: VIZIO VO42L No picture, No Sound

Thanks PB.
I check voltage across the main big cap. 398VDC when ON and about 172VDC when standby.
Most caps on the inverter are either made by Rubycon or Chemicon (KY). Is that a good thing?

After taking the pictures, I try to plug all connector back to probe for LDO regulator, I forgot to plug in the 2 connectors for master and slave inverter board. I check 12V and 24V. To my surprise, 12V line read 11.9V and 24V line read 24.5V.

So the problem is not the PSU. I need to do a load test on the 24V line to confirm that. For now, it's good

PSU ok, Main board seem ok, next one is the inverter set.

Attached Files

**CrappyCap** · 01-15-2011, 03:53 AM

Re: VIZIO VO42L No picture, No Sound

Time to check the inverter set.

I remember one post (#29) by Dgtech https://www.badcaps.net/forum/showpo...4&postcount=29 regarding checking for 4 mosfet along with the BD9897FS controller.
Well on the master controller all 4 and 2 on the slave read 8.45Kohm. Those are circle in RED. Within the spec as indicated by Dgtech. the other 2 on the slave card give weird reading. 1.6 ohm and 7.6 Ohm. Those are circle in Yellow.
Does that mean the controller chip (BD9897FS) is going south or only that 2 mosfet (K4075) are going on honeymoon?

Look like neither mouser nor digikey has that BD chip on hand.
Thanks guys.

Attached Files

**Dgtech** · 01-15-2011, 06:16 AM

Re: VIZIO VO42L No picture, No Sound

You are correct. This video driver chip is bad. It shorts out internally and gives a lower resistance on one or, in this case, two of it's four outputs. Once the chip is removed, with just the pads showing, you will see that the resistance check you made will go even higher. They should read 10K each. Place the new chip in, about 8.5K.

The chips I get are from in China. I buy them on Ebay for about $10 each chip. Sometimes you can find a seller here in the US that has a few. If you can find this then it helps cause the shipping from china takes a while.

I have a few here I bought in anticipation of seeing more of these TV's. I'll have to check my stash before I know if I can give up any. Check ebay first.

**CrappyCap** · 01-16-2011, 01:07 PM

Re: VIZIO VO42L No picture, No Sound

I try to remove the BD9897FS chip and end up lifted few traces on the pcb

Time to order a new set. It's 130 buck from Vizpart listed as upgraded version (6632L-0470N & 6632L-0471N) of the original 6632L-0470A (Master) & 6632L-0471A (Slave).

After remove the chip, the 2 bad mosfet is still reading bad and 2 good mosfet is ready about 10K. I guess the bad BD chip probably isn't bad, but a bad 2 mosfet instead.

**CrappyCap** · 01-18-2011, 11:15 AM

Re: VIZIO VO42L No picture, No Sound

Thanks everyone.
Just order new inverter kits (6632L-0470A & 6632L-0471A) from fleebay for 120 bucks shipped.
Let see if that fit the problem. Finger cross and waiting for new part to arrive

**Dgtech** · 01-19-2011, 07:39 AM

Re: VIZIO VO42L No picture, No Sound

Sorry to hear about the desoldering mishap.

Did you buy both master and slave replacement boards?

I have replaced one without replacing both before.

**CrappyCap** · 01-19-2011, 10:47 AM

Re: VIZIO VO42L No picture, No Sound

Well before start de-soldering, I already "knew" that I'm going to screw up that IC. I never deal with MSD before so it a good experiment. Next time I'll just get some of those ChipQuick kits.
I just order both master and slave. ShopJimmy want 75 bucks shipped for the slave. Fleebay doesn't have the slave I need, but have a set for 120 shipped. Both place advertised as "brand new". If thing work out and I have extra left. Maybe just keep it for "future need"

.
I may use the "broken" inverter and jump, modify to make it more "reliable" as posted by Phillips. Just something to experiment on free time.

**CrappyCap** · 01-25-2011, 01:05 AM

Re: VIZIO VO42L No picture, No Sound

New set of inverter came. Replace the inverters and I'm back watching TV

Before install the inverter, I did check 8 mosfet and they all read 8.56k Ohm.

Also note, new inverter set has same part number but revision 1.3 board whereas the old on was rev 1.2.

Thanks everyone for helping trouble shoot the problem and sharing info on fixing those problematic electronic gadgets.

**andyak** · 02-16-2011, 03:58 PM

Re: VIZIO VO42L No picture, No Sound

Hey Guys,

New here - good discussions!

I have same Vizio - same problem!

turns on, goes white - no picture.

I have checked out all voltages - ok - replaced power sup fuse - just in case - have good voltages all around and unit responds to remote.

Just read this thread and checked for the 8.5k readings - and lo and behold the slave inverter has one slightly low at around 7.3 and another really low - so I guess the chip is bad!

I also have ordered new set of inverters for $120 shipped -

Q - if they are new revision, should I install the replacement main inverter as well - or can I leave it in and just replace the bad slave?

another question - how the heck do you get the FFC - little flat cables safely in and out of inverter sockets?

Thanks in advance..

Andy

**Dgtech** · 02-16-2011, 05:03 PM

Re: VIZIO VO42L No picture, No Sound

I wouldn't worry about the flat cable unless there was some physical damage. You could have just changed the slave board but just in case, keep the master that you take out since it checked good. I have a Philips that I changed the slave board out. It worked fine for about four months and then the Master died for the same chip. I dont think it was a matching problem, I think the chip simply died. I have changed out a number of those chips now.

**andyak** · 02-16-2011, 05:16 PM

Re: VIZIO VO42L No picture, No Sound

Thanks - is there a specific way the little flat cables come in and out of the connector on the board? does the connector open up - I can't seem to get it to open....

**Randhj** · 02-27-2011, 06:38 AM

Re: VIZIO VO42L No picture, No Sound

New here first post. Same vizio vo42l also purchased from costco and died 2 years 8 months after purchase. Costcos concierge wanted 400 to come out and look at it, we got a local repairman to come out for a 100 and he said it was the 2 inverters and wanted another 200 for parts and 100 to install. Im not sure how he checked it, I was not here at the time its my grandparents tv. I would like to know the difficult of installing the two inverters. I have built my own desktops, and have handy man experience but poor soldering skills. If I get the inverters off auction site for 110 (not repair kit) is it just unscrewing the old boards and popping the new one in and clipping in ribbon? I do have a voltmeter as well if that can help me double check his diagnosis easily.

**PlainBill** · 02-27-2011, 08:28 AM

Re: VIZIO VO42L No picture, No Sound

Originally posted by Randhj View Post

New here first post. Same vizio vo42l also purchased from costco and died 2 years 8 months after purchase. Costcos concierge wanted 400 to come out and look at it, we got a local repairman to come out for a 100 and he said it was the 2 inverters and wanted another 200 for parts and 100 to install. Im not sure how he checked it, I was not here at the time its my grandparents tv. I would like to know the difficult of installing the two inverters. I have built my own desktops, and have handy man experience but poor soldering skills. If I get the inverters off auction site for 110 (not repair kit) is it just unscrewing the old boards and popping the new one in and clipping in ribbon? I do have a voltmeter as well if that can help me double check his diagnosis easily.

As I recall, Costco's Concierge service provides a 3 year warranty. If that is correct I would insist that they provide the promised service.

The common failure is shorted transistors on the slave inverter. Replacement is a fairly straightforward job, not much more difficult than replacing a motherboard on a PC.

PlainBill

**retiredcaps** · 02-27-2011, 03:13 PM

Re: VIZIO VO42L No picture, No Sound

Originally posted by PlainBill View Post

As I recall, Costco's Concierge service provides a 3 year warranty.

In Canada, Costco's Concierge service is 2 years. This would explain the service denial if poster is in Canada.

**vonwiggleding** · 02-27-2011, 11:40 PM

Re: VIZIO VO42L No picture, No Sound

Originally posted by Randhj View Post

Same vizio vo42l also purchased from costco and died 2 years 8 months after purchase.

Almost exact same date as mine went out, I purchased July 22 2008. It was my slave inverter board too, it whined like a stuck pig for 3 months before croaking. Makes me think Vizio knows they're selling garbage.

As Crappy said, I was told by concierge the 3rd year warranty is only added if you bought with AMEX.

**Randhj** · 02-28-2011, 03:44 AM

Re: VIZIO VO42L No picture, No Sound

Yea, we paid cash so no 3rd year warranty. Im gonna order from vizparts later today. I opened it up yesterday to take a look and it seems very straightforward. Ours was buzzing for a lomg time too, I guess we should have called while under warranty for buzzing.

**PlainBill** · 02-28-2011, 07:13 AM

Re: VIZIO VO42L No picture, No Sound

Originally posted by vonwiggleding View Post

Almost exact same date as mine went out, I purchased July 22 2008. It was my slave inverter board too, it whined like a stuck pig for 3 months before croaking. Makes me think Vizio knows they're selling garbage.

As Crappy said, I was told by concierge the 3rd year warranty is only added if you bought with AMEX.

Well, as much as I hate to defend Vizio, the inverters are supplied as part of the LCD panel, and are manufactured by LG Electronics. LG is aware of the problem, and has already issued a modification kit for the inverters.

PlainBill

**CHENG39** · 03-16-2011, 08:48 PM

Re: VIZIO VO42L No picture, No Sound

These experiences are all very similar to mine. About 27 months into ownership and the screen went black with no advance indications. Sound remained. I did the flashlight check and was relieved to see the picture. I ordered new master/slave inverters from vizparts (~$130 for the set) and replaced them. No change. Against my better judgment, I ordered a power supply and replaced it. Again, no change. I searched the web again and found this thread and began resistance checks on the old inverter mosfets. Similar indications on the slave board (one read a short, while the others were in tolerance). Retraced my steps and replaced the original P/S and new inverters. Gave it one more try and I'm back up watching college ball. Not sure what I missed on the first go 'round, but I also wondered some about the flat connectors (whether I was making good contact).

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