Philips 55PFL6158 - 2 blinks - Code 53 - QFU 1.2 - CPU reflow - IR6500 rework station

I am getting the hang of those QFU boards. :-)

Update: I have revived another two of those boards recently with the same symptom by reflowing the CPU.

This Philips did not show any sign of life except for the standby LED, which responded to an infrared remote. The 2-blink would show after a while and the level 2 code in SDM mode was 53.

Quick reminder: if you attempt to repair a QFU Philips, you must have a logging adapter, otherwise you are blind. See this blog post.

I plugged in the logging adapter and I got this in many repetitions until the two blinks came:
....
20:49:53.548 0x00000002 page is reading 
20:49:53.557 0x00000000 0x00000000 0x00000000 StartUnit/EndUnit/offset 
20:49:53.557 Reading out data: 
20:49:53.557 00 unit: 
20:49:53.557 
20:49:53.567 
20:49:53.567 waiting ECC result ready 
20:49:53.567 00 bits error in the unit. 
20:49:53.567 
20:49:53.567 
20:49:53.567 {preboot} 
20:49:53.567 <000> 
20:49:53.567 <010> 
20:49:53.567 <020>K

That was it. Abrubt end.

To learn what was going on in a good TV I logged my 40 inch QFU1.2. The section where the dead device looped should look like this:

20:49:53.567 {preboot}
20:49:53.567 <000>
20:49:53.567 <010>
20:49:53.567 <020>KKG0G1 
20:49:53.773 <030>DDDDDDDDDDDDDD 
20:49:53.831 <040>secure 
20:49:53.832 Load uboot 
20:49:53.850 
20:49:53.884 
20:49:53.884 U-Boot 2009.01_Production (Jun 11 2013 - 10:29:06) 
20:49:53.884 
20:49:53.884 U�U 
20:49:53.911 NAND: NAND, size:1024MB, Micron(ID:0x2c,0x38), block size:512KB 
20:49:53.913 1024 MiB 
20:49:53.932 Env: NAND @ 0x01800000 
20:49:53.983 bootcmd1 
20:49:53.996 BOOTREASON=coldboot
...

So, the processor could not reach the point where it starts reading the main software, which is actually a Linux boot.

I suspected the SPI ROM first and swapped it. No change. Then I tried the NAND chip with an image from a 40PFL6008. No change.
The last option left was the CPU. I did not dare to reflow the whole board with its uncountable miniscule parts everywhere. I needed a tool with more precision.

I had my eyes on a BGA reflow workstation for a long time and this was the opportunity.
Here it is, the affordable IR6500 made in China (where else).

The preparation of the board was as follows:

• Remove the heatsink from the CPU. Use a heat gun briefly and it will come off easily.
• Do not put thick, tacky flux under the chip. I used to do this before, but realized that if the flux bubbles under the CPU while the balls are liquid, this can make the chip bounce and also it can cause balls to connect. Only thin, liquid flux, which does not accumulate under the chip and evaporates quickly, is suitable.
• Cover everything around the CPU with tin foil. Some instruction videos use a tape. I don't think this is necessary as this device does not blow hot air.

Reflow in progress:

The first test was almost successful. It started booting but something was wrong with the NAND flash that I swapped. Linux refused it. Because the NAND was not the fault in the first place, I put back the original and voila! It started up fine.

Last task: put the heatsink back on. The original adhesive pad got ripped apart. To make the sink removable I decided to glue a thin thermal pad between the CPU and the sink:

The glue stays somewhat flexible, yet it might be strong enough to make removing a glued sink from the chip an unpleasant work. I'd rather destroy the pad instead.

This all worked well. Hallo Frau Johansson!

I do like this TV. The LG panel produces beautiful, realistic colors. My Panasonic Plasma is still the king of skin tone, but I could totally live with this one. With the sharpening reduced to a minimum, that is. I also like that it can be switched to computer mode, which bypasses all extra image processing and pixel by pixel is displayed as is. This gives you a realistic impression which information an image really contains and how much these devices invent by themselves!

The sound is not bad either. The 6000 series is still a bit on the budget side. Stereo is not taking place. The 8000 and 9000 series have a lot more to offer there.

Improving the cooling situation

Philips has undersized the CPU cooling on all QFU chassis. The QFU1.2 is even worse than the QFU1.1. The CPU won't die from that, but the solder balls will break. Interestingly, the 1.1 seems to have different typical faults than the 1.2, yet both are caused by overheating.

This is an image of the back cover from a white 40 inch:

There is some convection going on. The air stream hits the CI socket (bravo!) and exits through a small portion of the upper grill. The dark streaks are dust accumulations on the footprint of the heat sink. Hot plastic attracts dust. This solution relies exclusively on air convection. The infrared radiation hits the plastic and in turn, being a bad heat conductor, the plastic gets hot, radiating back onto the device.

Without the back cover, at 21°C room temperature, the CPU gets 55° hot. That's okay. But with the cover on and in summer I estimate another 20° or more on top of that. That's almost 80°. Too hot for sustained function, if you ask me.

I found no way to attach a larger heatsink to the CPU. There is just no free spot on the board where to fix it.

When I put the back cover on, I noticed that the thermal pad closed the gap between the sink and the cover. That was bad! Thermal death unavoidable and high danger of mechanical shock.

I cut out a rectangle at the sink position and glued a metal grid on it. Nothing beats a sink exposed to fresh air.  Infrared radiation and air convection in one. It is not exactly robust and does not protect the CPU too well, but unusual problems require unusual solutions :-D
There are more stable grids available in hardware stores, but those are are not fine enough.

One hour break-in. About 55°C constant. This is perfect. Identical thermal situation as with an open cover.

About the IR6500

This thing is a little rough around the edges as you might expect from a budget Chinese product.

The manual is funny Chinglish. I could figure out the meaning of most sentences. However, not all details are needed. There is one predefined program for leaded and one for unleaded solder. That's all I need to know. Press start and you are good.

The glass shield on top of the downside heater is bullshit. It reduces the function of the heater plate drastically. The preheating is practically ineffective. I ran the program with the top heater swiveled aside. The board made it to 45°C on the top side. That's a joke. Proper pre-heating begins with 80 or more! I think I am going to remove the glass.