Re: SHARP LC-46LE730E - no backlight, no picture, no sound
Okay, so I changed the FET, and the TV is still dead.
S1-D1 pads resistance: 89 Ohm in one direction and 100 Ohm in the other. You were right, it isn't the problem. After I changed the FET I didn't power up the T-CON with a PSU to check the voltages because I didn't want to mess with it yet.
So I went back to the IC9701. I could cause the same backlight turning on thing than previously. (touching the IC and sometimes the backlight started to blinking real fast, and sometimes turned on for a few secs (like...
CMG97
Member
Last Activity: 03-26-2020, 08:52 AM
Joined: 02-22-2020
Location: Budapest
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
Voltage drops:
D901:
One way-0.457V
Other way-Open loop
D902:
One way-0.459V
Other way-Open loop
D906:
One way-0.462V
Other way-Open loop
D907:
One way-0.564V
Other way-Open loop
They all seem fine to me.
I'm not sure whether these diodes are related to the backlight or not, but I can turn on the backlights manually by shorting the PS_ON and BS_ON pins and it turns on fine. (Software won't set the BS_ON pin high, so that's the...Last edited by CMG97; 03-25-2020, 11:37 AM.Leave a comment:
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
It was 0.049 V when the FET was soldered in. I desoldered it and measured it alone. (The voltage drop between the pads are 0.045 V/0.066 V now. )
The voltage drop between the FET pins (FET desoldered) are the ones I wrote above.
I can confirm the connections you mentioned.
D2: 12VCC (PANEL_VCC)
S1: GND
D1 is connected to S2
I will try to follow back the route of the D1 pad to find a diode or transistor. Sadly I don't have a schematic for the T-CON.
Edit:...Last edited by CMG97; 03-25-2020, 10:31 AM.Leave a comment:
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
Update:
I desoldered the FET301 component. Sad news. The voltage drop I measured was the voltage drop through the board (It was very close to 0 V but not exactly 0 V. I can reproduce the same numbers through measuring the pins on the board without the FET).
The FET is fine in my opinion:
S1-D1: 0.546 V
D1-S1: open loop
S2-D2: 0.545 V
D2-S2: open loop
I will change it anyway, but I'm pretty sure this won't solve the problem. I'm out of ideas for now. If you have...Last edited by CMG97; 03-25-2020, 08:19 AM.Leave a comment:
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
I will use the notations used on the wiring diagram.
So after I hit the Power button the PANEL_VCC jumps to 12V (actually it's less after my multimeter shows a value) and then immediately it starts to decreasing slowly. This is a transient state.
The values shown on the diagram were my readings after powering on the TV and waiting for a few mins.
On PANEL_ON_P1 I cannot get a proper reading, since I don't have an oscilloscope. My multimeter only shows a sec hesitation...Leave a comment:
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
I remeasured s1-d1 after shorting the s1-g1. Also did it after turning it off, unplugging and waiting. Same results with the voltage drop. I have ordered the parts. Should get it by wednesday, will get back to you if I succeed and the TV starts.
Thank you for your help!Leave a comment:
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
Thank you for your suggestions!
I did the measurements.
The T-CON power supply part:
The FET301 voltages (After 5 mins of powering on the TV):
The FET301 voltage drops:
I think the 0.069 V and 0.046 V voltage drops are indicating that this component is probably faulty. The T-CON power part seems to be OK. It gets a consistent 12.1 V power and only the control signal from the FRC is missing. Based on my previous...Leave a comment:
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
Thank you for the manual, I have this service manual and linked this in my 2nd post (bottom) and using it. (Source of the pictures I edited)
I unplugged the tcon as you suggested!
So without the TCON plugged in the voltage on the 12V pins are reaching about 10-11V immediately after powering on and then slowly decreasing. (It's like a capacitor loosing charge slowly)
With the TCON plugged in, the peak is about 1.5 V and then slowly decreasing again. I think the reason I measured 0.5V is because...Leave a comment:
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
I think the old mainboard is broken. I can start it in service mode and I can turn it off with the button in this case, but if I start the TV in regular mode, then the TV simply shuts itself down after 30-60 secs. With the new mainboard though, I can start it in a normal way and turn it off properly. It is possible that I might be stuck in an initial setup menu with the new mainboard, and because of that I can't produce any sound through a HDMI cable. (Speakers are powered with 6.09 volts after starting)
I...Leave a comment:
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
Thank you, I forgot to change the last line after pasting it. I edited the post, so now it’s correct. The mainboard doesn’t send backlight on signal. The only way I can turn the backlight on is by shorting it with the PS_ON pin. In this case the backlight turns on, but no picture on the screen....Leave a comment:
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Re: SHARP LC-46LE730E - no backlight, no picture, no sound
Thank you for your answers!
I can make pics with higher resolution if needed.
Original mainboard:
New mainboard from an LE542E:
PS board:
T-CON board:
Overall pic:
Pins on PS-board:
So, I checked the voltages with both mainboards:
With original:
DIM - 3.21 V (On) - 0 V (Off)
PWM1 - 3.23 V (On) - 0.46 V (Off)...Last edited by CMG97; 03-20-2020, 03:10 PM.Leave a comment:
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SHARP LC-46LE730E - no backlight, no picture, no sound
Hey everyone!
Initially, my TV didn't want to start up sometimes and had to restart several times to have a picture and start up. One day it stopped completely and would not start since then. If I press the turn on button the blue led starts to light and after 30-60 secs (didn't measure it) it turns off completely. Except if I start it in service mode(plugging it in while holding input + vol-), because in this case it won't turn off unless I press the power button.
I started with observing the power board and everything seemed to be fine. I checked all the voltages on... -
Re: New Members - please post your introductions here
Hi everyone!
I’m from Hungary and I’m here to learn more about practical electronics through fixing my stuffs. Currently I’m trying to repair my TV and looking for some help to understand the source of the issue.Leave a comment:
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