- Joined Apr 2, 2009
Next was to modify the out puts of sharp PSU. A quick reference to the data sheets of the regulators used in the PSU secondary showed it's easy to generate at least 5V difference as long as the voltage does not go below it's rated output, since these were switched mode regulators. it was easy.
The 3.3V was not necessary, so it's regulators were omitted and the fault detecting circuits were bypassed for this output and the 6V feed back was increased to decrease the output to 5V. Since the sharp PSU and the benQ regulators were of type 1.5A current ratings, It was not necessary to even check if the supply could handle the current, something I learned over the years, Just by looking at the regulators, transformer, inductor and the caps I can assume it's power handling capacity. The Audio supply is OK since I don't need them but to test, and almost all audio amps can handle a change in plus minus 5V or so provided the out put level is kept low.
Here is a pic of the benQ back before the removal of it's supply.
Now with ever 5V added, it was time to see if the BenQ processor worked switching it's control terminals. There was only one switched out to the PSU. All the rest are powered up when the supply switches on.
The Sharp Inverter has more terminals than I bargained for, at least seven, as a rule of thumb, there will be +Vcc, GND, fault feed back and the back lit brilliance control, still 3 is left and I have no idea what the heck those 3 does, so a quick fiddling was necessary. It seems that the control pin has two inputs which has a high input of 3.3V to be activated for the inverter to power up. The Inverter 400V DC is separate and is powered when the PSU switches on, so that was settled, now since I am using the sharp PSU, getting the supply for the low voltage side of the inverter was no problem, all I have to do was to route the BenQ signals to the sharp Inverter, and I shorted the two control inputs.
Secondly the 5V was applied to the DSP, and for the time being I used the audio amp to test audio and the power for this was also no problem. The two pins left from the inverter was, as I assumed to control the back light brilliance to acomodate for the room illuminance and the likes and is left to be checked once I get into the system menu of the TV.
So after carefully mounting the sharp PSU to the BenQ chassis, and nicely cable tying the wires, crossed my fingers and powered.
The stand by light lit, and the press of the power a few relay clicks and viola!!
The TV came to life, and it stayed on. I was soooooooooooo happy.
Below is the final assembly, notice the cable routing and the 5V supply at the back of the main PSU. ( Sorry for the dark picture, I forgot tht the flash didn't go off)
A real funny thing happened, remember about the left out pins of the inverter brilliance control, well guess what, when I played with the menu settings, the back lit works, when switched from dark, normal to bright.
And to think that there is no connection that could possibly control that what so ever, I mean I made no connection except the 400V DC, 12V Vcc, GND, and the joint two control pins. So how the heck is the BenQ DSP is controlling the sharp inverters light output. ****Miracle****. what else. . .....what do you think. Still, I ain't touching that part since it's working, one rule, if it works leave it.
A close up
Notice the front screws, well the TV was used in a place without AC, and it is pretty hot here in Maldives.
So the plastic chassis was very brittle, and most of the screw holes broke when I tighten the screws. So this has to be done if I were to hold the LCD in place. (Notice the cracks too )
The screws were counter sunk into the frame and may be later I would use a thin black plastic with a nice design to cover up those screw heads. I could come up with a name too, since I can engrave plastic like factory made.
Since this is not now a BenQ nor a Sharp, what would you recommend, I mean a name for my flat TV.
The LCD passed the tests with flying colors, the picture is brighter than I expected and 1080i, 720p and HD ready too . Switches itself off ones there is no sync.
Comments are most welcome.