TV Repair Questions? Ask a TV Technician
Wow, pretty fast response.
It doesn't appear to be flashing a "code". It just flashes very periodically, like every one or two seconds.
The TV is about one year old. Great picture until today.
I need to find when I purchased it as the warranty direction would be good.
If it was over one year how do I contact you to continue with the answer?
Okay, it is out of warranty and it is a model 46XV545U. I took off the back and found fuse F820 on the power supply board blown. The power supply board is marked PE0626 C and V28A00084501.
The fuse is a time delay 2.5A 5x20mm (marked T2.5AL 250V). The fan spins easily and even if locked I doubt would draw enough current to blow a 2.5A fuse.
The fuse that is blown does not appear to be the primary input fuse. I will see if I can find a fuse at my work otherwise I will need to buy off the internet (Digikey, Mouser, etc.) which will take a few days.
As this is a time delay fuse it usually means that there are surge currents, usually at initial turn on. This died during operation so I'm thinking I've got something bigger than a fragile fuse. What say you?
Okay, they do some really weird stuff in breaking out their power supplies. The fuse is near a STR-Z2589 (Q860) resonance mode power supply chip near transformer T860.
I'm having difficulty following the voltage regulation as it appears to be done on two boards. I'm guessing the STR-Z2589 is generating the 24V that goes to the video input / processing board (where video inputs are located). But the 12VLCD is also distributed from this board and so is the fan power.
There is a second board PE0563A / V28A000736A1 that appears to be generating 5V, 12V. In essence, we have two power supply boards but power is distributed on one board but might have been generated on the other.
I've ordered some T2.5A fuses that should arrive on Saturday or Monday (Denver doesn't have much in the way of component vendors). I do have a 3.125A fast blow and a 2A slow blow that I could try.
Okay Tim, I replaced the T2.5A fuse with a T2.0A fuse. It blew almost immediately.
The fuse appears to be on a +48 Volt line. With the blow fuse in place I've got +5V but the +12LCV & +24V are around 3V (fluctuates with my Fluke but without breaking out the o'scope I can't really tell).
The weird thing about the blown fuse is when open:
the input side of the fuse is around 49V
the output side of the fuse is around -35V (referenced to fan ground)
After a few seconds a relay kicks in and the fuse input voltage goes up to something like 68V and the output side goes to almost ground.
Another weird thing:
If I spin the fan (it is trying to spin with the 3V) before the relay kicks in it will keep spinning (not surprising). The weird part is I think the TV believes it working as the green LED on the front panel is lit solid and the yellow LED is OFF. The fan will continue to spin and the green LED solidly lit for many minutes.
Hopefully the correct fuses will arrive tomorrow or Monday but I'm thinking either my power supply board PE0626 C / V28A00084501 is bad (bad STR-Z2589 or the transformer it is driving) or the Load that it is driving is bad.
I don't have schematics, but the fuse appears to be right close to the ac input. There are a couple of transformers (T820 & T821) and some TO220 diodes (D820 & D821)mounted on a heatsink and a huge 220uF 450V electrolytic cap (C820). I would expect this supply drives some serious current ~ why else would you use a 220uF cap and have diodes mounted to a big heatsink.
Thus, if the load is removed by a blown fuse the big cap would charge to the peak rectified voltage. When I remove ac power it takes many minutes for the voltage to drop at the fuse input, meaning there isn't much bleed current (i.e. bleed or discharge resistor).
What I really don't understand is the minus voltage on the fuse output side when blown. Maybe if there is something really inductive or ??
To make a guess, could this be driving the ballast for the CCFL or maybe is part of the ballast?
P1010327.jpg shows the section of the board with the blown fuse. The ac input is on the lower left corner of the board. The blow fuse is on the lower right just to the left of "TOSHIBA". The red ./ black / yellow wires are to the fan. The heatsink towards the bottom center is attached to two transistors (Q820 FCPF 11NGOT, Q821 FCPF 11NGOT) and one diode (D821 N2206) from left to right (I thought it was two diodes and one transistor).
P1010324.jpg shows the open back. The blown fuse is on the green board to the right with the fuse in the upper right. The second power supply board is the brown board to the left.
I followed the wires and believe this portion of the power supply drives the backlight inverter. I also found a web site the sells the boards in question [tvparts4less.com].
The backlight inverter is a Samsung part (per logo on the PCB) as is the LCD panel. Per the web site the Backlight inverter is a part number SSI460_22B01. It wouldn't surprise me if the backlight inverter is bad which might have damaged the power supply.
I've found another web site that has the Backlight inverter as a Samsung LJ97-01669A.
Open side of fuse to fan ground is approx. 10.2M ohm.
If I measure 24VINV to ground I'm obviously charging some capacitors so the resistance is increasing with time. But it gets to over 1M very quickly.
Going with my troubleshooting skills:
I've got a blown fuse on my power supply that generates 24V and 12V.
The 24V goes to the backlight inverter and I don't know what else.
The 12V drives the fan and I don't know what else.
But no matter where these voltages go and what they supply the main processor only verifies they are present by the turning of the fan. So I would assume they are for functions not necessary for the operation of the processor.
Now I don't know why my fuse is blown. The power supply is a resonance mode switching design which makes troubleshooting difficult. If the load draws too much current, the transformer is damaged, the switching transistors or output rectifying diodes are damaged they all result in too much current draw at the primary side of the transformer.
From the fuse I can determine that this switching supply is somewhere in the 100 to 110W range (49V & 2.5A fuse). The items that I'm aware of that would require 24V or 12V and high current in an LCD TV are the backlighting & LCD panel IR heating. I would expect that both of these functions would be generated by the backlight inverter.
Switching power supplies can be very robust if designed properly. The same for the backlight inverter as it is also some sort of switching power supply I would assume.
Should I just replace both the backlight inerter and the power supply board and be done with it?
I think I'll wait until I get the correct fuses.
Then I'll disconnect the backlight inverter and replace the fuse. Apply power and see if I've got voltage regulation out of the switching power supply.
But from "tvparts4less.com" I can get:
Rebuilt backlight inverter SSI460-22B01 for $174 - $75 refund for my bad board
Rebuilt power supply PE0626C for $174 - $75 refund for my bad board
So for about $200 I can be back up and running. I just don't know anything about the vendor. I could just be trading one problem for a soon to be other problem.
I don't suppose you'll devulge who you buy your parts from.
I replaced the fuse and disconnected the backlight inverter and applied power. Fuse blew within a minute meaning the power supply is bad.
I'll order a power supply but there is a connector that I've not seen and don't know how to disconnect. It looks like solid metal wires bridging between the two power supplies. It is in the center of the attached picture. Is it fixed on one side and disconnected from the other? Does it disconnect from both sides / ends? It looks a bit fragile and I don't want to damage it when installing the new board.
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