Picked up a 46" Sanyo from a needy family. Works great for 20 mins or so, then backlight goes out. Still have sound. Upon restarting picture shows back up for 5 min then screen cuts out. If I let it cool down it will stay on longer. Could this be CFL's wearing out and drawing to much juice when warmed up. Let me know where to start and I'll post any pictures requested.
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Re: Sanyo DP46849 Backlight Issues
Pictures of all boards and overall layout, Get a clear picture of the labels next to the connector going from the PSU to main.
We will be going through some voltage readings with a DMM to see what is dropping out when you lose the backlights -
Re: Sanyo DP46849 Backlight Issues
Ok, I work till 10:00, but took some pictures before I left. I'll take it apart more tonight and get more.Attached FilesComment
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Re: Sanyo DP46849 Backlight Issues
Its almost impossible to test the invertor board on this unit. The Power Supply and Video Boards bolt to the back panel and the Invertor Board bolts under the panel. Testing while powered up is going to be a task. Taking new pictures now, because I realized that some were terrible.Last edited by Thorsbolt; 05-26-2015, 09:24 AM.Comment
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Re: Sanyo DP46849 Backlight Issues
Ignore the invertors for now, We need to check voltages on the PSU first.
Meter set to 20VDC can you test the BL_ON pin when the backlights fail.Comment
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Re: Sanyo DP46849 Backlight Issues
check for cracked soldering on the power and invertor boards.
it sounds thermal and that usually ends up being fractured soldering.Comment
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Re: Sanyo DP46849 Backlight Issues
As mention by stj, it appears to be a thermal problem. Try heating up each board with a hair dryer while the tv is running to see if you can accelerate the shutdown process. This will hopefully help you narrow the board that's causing the problem.Comment
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Re: Sanyo DP46849 Backlight Issues
I agree with the Thermal Diag. While working the BL On reads 3.27V DC.
Failed it reads the same.Comment
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Re: Sanyo DP46849 Backlight Issues
Yeah seems to be thermalComment
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Re: Sanyo DP46849 Backlight Issues
I'm gonna hit the power supply and video boards with a hair dryer tonight, but the invertor board is buried. Is there a good way to ohm test it?Comment
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Re: Sanyo DP46849 Backlight Issues
Better pics to help diag.Attached FilesComment
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Re: Sanyo DP46849 Backlight Issues
These 3 are of the back of the power board. I see no compromised solder but I did see too slightly discolored spots.Attached FilesComment
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Re: Sanyo DP46849 Backlight Issues
some bad joints there.
look for faint rings around the joints like a haloComment
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Re: Sanyo DP46849 Backlight Issues
Well I can see alot of bad solder joints, what I also see is what look like something was spilled on the board. What should I use to clean it and should I focus on fixing all the solder joints or getting a new board?Attached FilesComment
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Re: Sanyo DP46849 Backlight Issues
fix the joints and then clean the flux off with IPA
fixing joints costs nothing, so it's always worth a try.Comment
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Re: Sanyo DP46849 Backlight Issues
I fixed some solder and cleaned the board. TV still shuts down, but I am able to access the invertor now when it's powered up. Any further testing?Comment
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Re: Sanyo DP46849 Backlight Issues
Also the three steel bars get exceptionally hot on the back of the power board. Like they'd burn you. I'm pretty sure the for heat dissipation. But should they get that hot?Comment
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Re: Sanyo DP46849 Backlight Issues
I ran a very low CFM fan over different boards to keep them cool and found the Main Board beneath a heat shield is getting to hot and shutting it down. It seams a finned block of metal had afoam strip on it to protect the board... It was holding heat. I removed it and the TV stays on. I'm still monitoring it. I will send a picture.Comment
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this tv is throwing me for a loop. do samsung tvs no longer have the backlight self test feature built into the power supply?
i tested the backlight with my LED tester and it lights up both strips. one of them reads 100v and the other reads 63.7v.
unplugged mainboard from power supply but left backlight plugged in, and then plugged psu wall power in. expected to see backlights light up but see nothing.
according to how ive diagnosed in the past, this would almost always be a bad power supply. replacement power supply was cheap like 20$ from ebay. but still i get not even... -
I have two Acer ER320HQ monitors. Both have dark background (I presume backlight issues) in on the left and right hand sides of the screen. Otherwise image is clear. Can these be repaired? The monitor is supplied externally with 19v DC and I have confirmed that supply is good and stable. Any further thoughts or pointers?...12-18-2024, 06:09 PM -
Hello Everyone.
Glad to be a member here! I am pretty new to working on laptops. I was hoping I was going to able to fix this one, but I am having some problems...
This laptop works perfectly with a HDMI monitor hooked up to it. Here in lies the problem. No backlight! So i figured, replace the screen/backlight assembly. Then I had very dim video (could be seen with a flashlight) but still no backlight. Found after doing some homework that it had a blown ferrite bead, which I replaced. Like an idiot, I forgot to unplug the battery, and when I was hooking back up the 30 pin cable,... -
I bought this p2210f dell monitor to fix. Schematic is the same as p2210.
Behaviour is that monitors comes on but then backlight switches off almost instantly. If I look with flashlight I can still find the "No signal message". So definitely a backlight issue. Trying to advance the issue I proved that the protection circuit is switching off the backlight by shorting out C3 and resistor to disable the INL chip then re enable by removing the short.
This is where it gets interesting. When I disassembled the monitor to solder leads on c3 capacitor I noticed the backlight flickered... -
Hello all,
Am trying to figure out this backlight issue with this A1990 Macbook Pro.
Tests performed:
There is no backlight even with a good screen.
Backlight IC is receiving the correct support voltages.
Fuse F8400 ok
Current sense resistor R8400 ok
Backlight IC is receiving 3.3V on enable pin.
Backlight IC receiving voltage from PPBUS_G3H, aprox 12.5V.
Backlight IC receiving 5V from PP5V_G3S
Backlight IC BKLT_SCL and BKLT_SDA both measure 0.545V diode mode to ground
I2C_BKLT_SCL and I2C_BKLT_SDA both measure...
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