Add philips 42inch repair project
BIN
content/projects/repair-philips-42pfl6057h-12/bga-cracked.jpg
Normal file
After Width: | Height: | Size: 42 KiB |
BIN
content/projects/repair-philips-42pfl6057h-12/featured.jpg
Normal file
After Width: | Height: | Size: 1.2 MiB |
BIN
content/projects/repair-philips-42pfl6057h-12/fusion-soc.jpg
Normal file
After Width: | Height: | Size: 5.3 MiB |
85
content/projects/repair-philips-42pfl6057h-12/index.md
Normal file
|
@ -0,0 +1,85 @@
|
|||
+++
|
||||
date = "2019-02-10"
|
||||
title = 'Repair: Philips 42" 3D LED TV with Ambilight'
|
||||
tags = ["repair", "audiorepair", "philips", "tv"]
|
||||
categories = [ "Audio Repair" ]
|
||||
summary = 'Last week I started a new repair project: a 42" Philips TV. The power supply was obviously defect, but I ran into another problem as well...'
|
||||
[image]
|
||||
focal_point = "Center"
|
||||
+++
|
||||
|
||||
I've done the occasional television repair in the past. Mostly Philips TVs with the '3 blinks' problem. When the power supply of a
|
||||
Philips TV is defective, the main board will detect this and blink the stand-by led 3 times to indicate this problem. Power supply issues
|
||||
I can fix - mostly.
|
||||
|
||||
So, I found this Philips 42PFL6057H/12 TV on Marktplaats. Instead of the '3 blinks', this TV did absolutely nothing. Another clue that
|
||||
the power supply is probably toasted.
|
||||
|
||||
## Step 1 - Open it up
|
||||
|
||||
First thing is to remove the back cover of the TV. There are a dozen or so screws on the back. These, together with two cables for the
|
||||
buttons and ambilight, expose the power supply board and main board.
|
||||
|
||||
The exact workings of how a Philips TV boots up when power is first connected is a bit more complex than what I'll describe here (read the service manual if you're
|
||||
interested). When the power cord is connected, the power supply will generate a 3.3V stand-by voltage. This is enough to power the 'Fusion' chip
|
||||
on the main board. The main board will then signal the power supply to start the 12V rails.
|
||||
|
||||
So, the first order of business is to check if the 3.3V is there. It wasn't. Careful probing revealed a shorted dual-diode package. Luckily, I
|
||||
was able to replace this part, as another power supply board from a previous repair had a similar dual-diode.
|
||||
|
||||
This brought back the 3.3V, but now I _did_ get the 3 blinks, as the power supply was not able to provide 12V. Some further investigation
|
||||
revealed that one of the control ICs on the power supply board seemed damaged as well. This part is hard-to-get and I opted to purchase
|
||||
a replacement power supply board.
|
||||
|
||||
## Step 2 - Why won't it work!?
|
||||
|
||||
With the power supply board replaced, I could measure 3.3V and 12V from the power supply. However, the stand-by LED wouldn't turn on.
|
||||
The TV _would_ respond with a blinking LED when I used the remote control on it - but it would _not_ turn on.
|
||||
|
||||
Some googling revealed that this is a main board defect and can't be repaired. It's recommended to replace the main board.
|
||||
|
||||
Well, I already replaced the power supply board, and I really didn't want to add further costs to this repair. Looking at the
|
||||
main board, it's not very complicated. There are some peripheral connectors and support ICs, an audio section, and this big
|
||||
BGA Fusion SoC. It's heatsinked on the front. On the back a piece of thermally conducting foam was used to sink some heat into the
|
||||
metal chassis of the TV.
|
||||
|
||||
So - nothing is obviously burnt. The TV does power up (so the Fusion SoC must be doing _something_), but it won't turn on.
|
||||
|
||||
If there were to be a problem, my guess would be that the Fusion SoC suffered some thermal stress and any one of the BGA
|
||||
connections might have been damaged.
|
||||
|
||||
BGA (Ball Grid Array) is quite simple. The IC and PCB have solder pads and you sandwich small balls of solder between
|
||||
them to make an electrical connection and secure the IC in place. This works great for SMD assembly of ICs with a
|
||||
high pin count.
|
||||
|
||||
One problem is thermal stress. When the IC generates heat, the PCB expands - and shrinks again when it cools off. In
|
||||
the long run this may also cause stress to the miniscule solder balls.
|
||||
|
||||
I found this photo on the internet that shows the exact problem. I don't have the equipment to inspect BGA's like this.
|
||||
|
||||
![A cracked BGA solder ball](./bga-cracked.jpg)
|
||||
|
||||
## Step 3 - Reflow
|
||||
|
||||
At this point the main board is unusable. I can either replace it or attempt to fix the possible solder ball issue I
|
||||
suspect.
|
||||
|
||||
Feeling adventurous, I removed the main board and powered up my heat gun. I have one of those (cheap-ish) soldering
|
||||
stations that come with an old fashioned iron _and_ hot air. I removed the heat sink and started carefully heating
|
||||
up the IC. I tried measuring the surface temperature of the IC with my infrared meter, but I did not measure
|
||||
above 160°C - too low to melt solder. Then I noticed that the solder on nearby resistors did melt.
|
||||
|
||||
![The actual Fusion SoC](./fusion-soc.jpg)
|
||||
|
||||
I stopped heating the board and let it cool for a few minutes. Re-installed the board and all the cables. Plug
|
||||
in the power. Press the power button. And there it was. A working TV.
|
||||
|
||||
## Step 4 - Cleaning up
|
||||
|
||||
The ceramic heatsink on the Fusion SoC was attached with adhesive heatsink tape. It didn't stick. Luckily there
|
||||
were mounting holes around the IC, so it was easy enough to construct something to keep the heatsink firmly
|
||||
attached.
|
||||
|
||||
Next, reinstall the back panel and reconnect the Ambilight cable. And I've got a new TV :-)
|
||||
|
||||
![Working TV](./featured.jpg)
|
After Width: | Height: | Size: 18 KiB |
After Width: | Height: | Size: 44 KiB |
After Width: | Height: | Size: 35 KiB |
After Width: | Height: | Size: 15 KiB |
After Width: | Height: | Size: 41 KiB |
After Width: | Height: | Size: 26 KiB |