sanyo dp46142 backlight issue.

[hicksvilleshick]

Yeah, 1st post. Yeah, not a component fixing kinda guy, not scared to work a soldering iron, but ain't done it much, and ill equipped for such things. But I'm hoping you guys can point me in the right direction on this tv...

I've determined the backlight on my 46142 shuts off when it chooses, I've replaced the backlight inverter board/led driver and have the same issue.

TV powers on and will work for a varying amount of time, then the backlight goes out, picture and sound remain, tested by the flashlight test.

Since swapping the new inverter/driver out and putting the old one back in, the tv will run the backlight for a varying amount of time, about 1-1.5hrs then backlight shuts off. If I power off the tv and repower it, the backlight comes back on for anywhere from a few min to just over an hour. Then shutting it off and turning it on will only result in the backlight just flashing once while it's starting up.

Troubleshooting indicates it's the inverter/driver. The replacement was supposedly seller refurbished, so I gotta wonder if thats the issue, but the tv does the same thing with both boards so I also gotta wonder if something else is causing the backlight to kick off.

Just looking for ideas as to what to look at next or any insight. I'm working on returning the refurbed board, not sure if I should exchange for another one or go for the refund.

Many thanks.

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

Upon the suggestion given to me I'm going to pull the powerboard and check all the solder joints... beyond that I'm still without a clue as to why or how to correct this issue.

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

went and borrowed a decent multi-meter.

now to figure out what to look for.

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

went and borrowed a decent multi-meter.

now to figure out what to look for.

Checked the powercord and it seems fine.

shop jimmy guy says

Either the leds are bad in panel, or the power to the led driver board is cutting out, you will need to monitor the led driver/ power connections to see which is cutting out, it could even be the main dropping the led on drive voltage. Power supply could be bad, could be main, monitor the voltages to see.

ok great, how do I go about doing that?


This is the powerboard. connector at bottom right goes to mainboard, connector and direct right goes to driver/inverter. there is then a connector on the bottom of the driver/inverter that goes into the back behind the metal.





mainboard has a connector that goes to what I believe to be the t-con board, I can't seem to get that connection loose on the mainboard end, I've tried and it feels like I'm going to break it if I pull any harder unno: then a connector going to the speakers, and the ir eye/front led, and of course the pwbrd. there is not a connection between the mainboard and the driver/inverter.


I'm totally ok with getting a replacement board, but I'd like to know which one to get before I do, I don't have funds to just buy them all. Already tried the driver/inverter board, got the same results.

all this dinking I've been doing with it, it no longer runs the backlight any longer than a flicker at startup.

Please. help me. lol I'm afraid my children are going to murder me in my sleep if I don't get this thing back up and running.

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

checked voltages from pwrbrd to inverter and mainbrd. swapped back in the new inverter/driver and same result, tv powers up backlight flashes but won't stay on. I have not been able to find a backlight on pin on any of the hardware.

dim 1.9 (all voltages were the same from pwrbrd to both the inverter and mainbrd.)
acd 0
pwr 3.2
inv 3.2
24v 24.1

one thing I have noticed is that it's arcing when I plug it into the powerstrip. nothing else on this powerstrip does this. I wonder if that means somethings fukky in the powerboard. unno:

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

Well I bit the bullet and bought the lamp we need for the DLP tv we've got so we'll have that one up and running... I guess I'll try to find another knowledge source and try again.

Thanks for letting me post.

[tech2014]

Re: sanyo dp46142 backlight issue.

Are you getting your PFC voltage? I just fixed an LCD that had no backlight and I found that the PFC voltage was only 160V, should be about 360-375V. You can measure the PFC across the large filter cap. It should be about 160v in standby and about 375 fully powered on.

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

If you can tell me what cap or how to ID the cap I'll be happy to measure it. the only thing I measured was the pins for the connectors.

Are you talking about the big black barrel? (upper left)



we took the tv all the way apart to even try to find the backlights and couldn't ID them... got nervous and put it all back. I still have the back of the tv open tho. Forgive me electricity makes me a bit nervous. lol

[cliff_hootarski]

Re: sanyo dp46142 backlight issue.

Respect for electricity is good. You will be measuring voltage that can be Lethal.

The main filtering capacitor is the large "black barrel" thing. do you see the white
line going around the board? That is the "Primary (HOT)" side of the power supply.
Any voltage measurements inside that white line will be done with respect to "HOT"
ground. That would be the negative (-) lead of that main capacitor.

[budm]

Re: sanyo dp46142 backlight issue.

Can you please remove the metal shield of the LED driver board and take good pictures of the top and bottom side of the board?

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

Can you please remove the metal shield of the LED driver board and take good pictures of the top and bottom side of the board?

Gladly. Took 2 of the front just in case the reflection of the light was in a bad spot.





Back




Please let me know if these won't cut it and I'll happily get better ones.

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

Respect for electricity is good. You will be measuring voltage that can be Lethal.

The main filtering capacitor is the large "black barrel" thing. do you see the white
line going around the board? That is the "Primary (HOT)" side of the power supply.
Any voltage measurements inside that white line will be done with respect to "HOT"
ground. That would be the negative (-) lead of that main capacitor.

good to know. so to measure that ground to chassis, and run the red poker to connections from it to the board? Again please bear with my my component tinkering is very very limited, I'm a good parts changer tho, but I can't figure out what part to change. I want to make sure I'm checking things the correct way.

Thanks all for your responses, at least I can prove to the kids I'm working on it kinda and maybe they won't plot my murder...

[cliff_hootarski]

Re: sanyo dp46142 backlight issue.

No, any DC voltage measurements on the "Hot" side of the power supply, the negative lead (-) or your multimeter will be on the negative(-) lead of the main filtering capacitor. The positive lead will then be on any component you want to measure the voltage.

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

No, any DC voltage measurements on the "Hot" side of the power supply, the negative lead (-) or your multimeter will be on the negative(-) lead of the main filtering capacitor. The positive lead will then be on any component you want to measure the voltage.

Ok I'll have to get the good multi-meter back over here. The only one I've got right now is a analog one that I'm pretty sure maxes out at 250v...

[tocold4u2]

Re: sanyo dp46142 backlight issue.

sounds lije the logic board cutting the power off. ??

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

sounds lije the logic board cutting the power off. ??

ok so is the logic board part of the powersupply or the mainboard? Or am I off the mark altogether?

:chug:

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

Got the fancy multimeter back over here... but got a car that needs it's brakes tended to that will keep me busy most of the day, but anything that can point me as to what I need to get either powersupply or mainboard would be most helpful.

[hicksvilleshick]

Re: sanyo dp46142 backlight issue.

Anyone, ideas? Instructions?

[tech2014]

Re: sanyo dp46142 backlight issue.

did you check the PFC voltage?