Sharp LC-40LE540E - not booting - bricked software - revived via service mode and firmware update

This was my first Sharp TV. And as always with new devices, I spent too much time testing the wrong things. But hey, this is my hobby and I always learn something even when I walk down the wrong path.

The seller of this TV said that it suddenly failed and wouldn't start anymore. It was purchased early 2013. A bad capacitor was not likely. A panel failure just maybe. I suspected some failed semiconductor.

When I plugged in, the indicator light went blue. Nothing else happened. After about a minute it switched off. The power button on the TV would turn it blue for a longer while, but still nothing on the screen. The remote had no effect at all. The device did not go to stand-by, where the indicator would light up red.

Ok, I fetched the service manual from elektrotanya.com and opened it up:

Not much to see here. I nice big subwoofer. Reminded me of Philips TVs 2010 and up. Even the small speakers are identical to the Philips.

The service manual is nice. It contains the schematics for all DC regulator stages, fully zoomable board layout and schematics of the main board and the power supply (only basic schematics there).

First thing to try is the service mode:

Well, nothing worked. As I learned later, I should have been more patient. But then, I started my routine checks instead.

Power supply

5V stand by: check
12V: check
5.75V: check
BL_ON (backlight): low, means off

Aha, so the processor didn't switch the backlight on. As this TV has no diagnostic blink codes, this meant testing all the voltages:

I noticed that IC3701, the frame rate converter (FRC) was running too cold. This thing should heat up. That was suspicious.

All voltages checked out good. The FRC chip had all required voltages.

So on to the TCON board:

The supply voltage was missing! Where did it come from? On the main board there is a little control circuit with a FET, which switches the supply.

And guess where the control signal PANEL_ON_P1 comes from? The FRC chip! The chip has an EEPROM connected to it:

I took my scope and probed the EEPROM. Besides a short flash of activity on the clock line shortly after power on, there was nothing going on. I also tried the freezing trick I learned from norcal715 (my favorite repair channel) on YouTube with no luck. Did this mean that the FRC chip was dead? Oh dear.

In some desperation I browsed the net and came across a video I had already seen once. It is from Grand Pass TV Repair, another of my favorite channels. The guy is wrestling with a Sharp TV, which would wake up in service mode, but fail again after pulling the plug.
https://www.youtube.com/watch?v=fBWX34wTULw

I gave the service mode another try. After about 10 attempts, the TV suddenly woke up and I was able to enter the menu! It's quite nasty. The trick with the buttons won't work immediately, it takes a number of tries. With the remote it won't work at all. I was fooled big time when I first attempted this. :-( Could have saved me a lot of effort. That's my personal Sharp lesson.

So, I went to the ETC menu and tried "EEP Clear" and "EEP Clear B" to reset the non-volatile RAM (NVRAM). In both cases, the TV went black and switched off. However, it still would not turn on again properly.

Pressing END during the factory menu opened the standard menu. It worked totally normal. There was nothing physically wrong with this set. Pressing the stand-by button on the remote switched it to stand-by ok (red indicator). But still it would not start up again.

A factory reset did not help, so I finally decided to run a firmware update, now that I knew how to start up the set. And this finally fixed it!

Hallo Frau Johansson!

So what exactly was wrong with this TV in the first place? No idea. The software somehow bricked itself. Luckily, there were ways to unbrick it, in contrast to the silly little Sony I tried to revive earlier this year.

This is a nice TV. The colors are good. The blacks are very dark. The sound is full thanks to the subwoofer. It may not have the fancy looks with its plastic case, but it has qualities!

I spotted some cheap capacitors on the power supply. They are all the same type, but one of them looked different. It is not easy to see on the image (the little, standing ones).

Desoldering is a breeze with my brand new pride and joy, the ERSA i-Con soldering station. This device is just awesome. Soldering is smooth like cutting through butter with a hot knife.

The 2x40 watts chip-tool makes desoldering a snap:

The left one looked slightly more bulged:

The capacitance values measured ok. The ESR was not really exciting but the caps measured different. The indispensable Blue ESR Meter in action.

For what reason ever, they are 47µ 50V, even though the maximum voltage there is 12V. I swapped them with some decent Nichicon HD 100µ 25V.

Ok, this TV is now ready to run just fine for a couple of years!