Sharp LC-C4655U Flashing OPC and Power lights.

**berrmich** · 08-22-2023, 07:27 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

Q9701 has 3.3 on pin 4
Pin 3 has 3.3. only if I start the tV with channeldown/volup
Pin 2 acts the same but 2.7V

Looks like I need to flip the board to check those fuses? Of note, I only get power to the inverter board if I have that jumper to PS_ON. Need to go to bed.

Let me know what to check next. Thank you so much for your help! Learning a lot.

-Mike

**R_J** · 08-22-2023, 07:53 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

If ch-/vol+ gives 3.3v on Q9701 pin3 it should give more than 0.7v on PS_ON

If you can get inv60v to the inverter board, just check for the 60v on the two jumpers near the fuses, L7500A and L7501A.
You can try unpluging LB plug and see if the tv turns on (this may or may not work)

**berrmich** · 08-25-2023, 04:06 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

Still 0.7 v. Not sure why. No I do not get 12 or 60 at the plug unless I jumper the pins. I only get the 0.7V if I force the TV ON. If not I get the blinking lights and 0V at PS_ON.

**R_J** · 08-25-2023, 04:37 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

Did you check the inverter fuses or check if there is voltage at the two jumpers?

If you look at the main board schematic, Q9701 outputs 3.3v on pin 3, then there is a 1K resistor to PS_ON and also a diode, D9701. If there is an OV_VLT error it will turn on Q9702 pin2 causing pin6 to go low, taking PS_ON low as well.

You would need to check the voltage on OV_VLT (D9702 anode) or check pin 2 of Q9702

**berrmich** · 08-25-2023, 04:42 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

Here is what I checked.

I checked L7500A and L7501A Both have 60V but only when I jumper.

Attached Files

**berrmich** · 08-25-2023, 04:45 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

Q9702 Pin 2 - 3.2V

**R_J** · 08-25-2023, 04:46 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

That means the two fuses on the inverter are ok. but there could still be a problem on one of the inverter boards

**berrmich** · 08-25-2023, 05:10 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

Anything I should check on the inverter boards?

Not that it's much of a surprise but the voltage at the 1K resistor mentioned above is 0.7V

**R_J** · 08-25-2023, 06:13 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

If you force the power supply on, what are the voltages on the LB connector on the inverter, there are four wires, one is ground so the voltages on the other three should give some information as to the state its in.

There is 3v on one side of the 1k resistor and .7 on the other likely due to Q9702 being turned on and D9701 cathode taken to ground and you are measuring the voltage drop across D9701 and I can not see that an inverter error will cause this problem. You would need to check the voltage on OV_VLT (D9702 anode) or check pin 2 of Q9702 to see if that line is high or low.

Maybe there are two problems, one on the main board and one with the inverter/ccfl backlights

Do you ever get a flash of the backlights if you force the power supply on?

**berrmich** · 08-25-2023, 06:51 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

D9702 is 3.2V

No power to any of the LB connector wires with no jumper.

No power to any of the LB connector wires with jumper (60V still working to the inverter)

Never had flash of light.

**berrmich** · 08-25-2023, 06:53 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

Of note the .7 is before and after the resistor.

**R_J** · 08-25-2023, 07:55 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

If D9702 has 3.2v then there is a problem with one of the regulater voltages on the main board

Of note the .7 is before and after the resistor.

This must be when you are not using the CH-/vol+ to turn the tv on because in post #21 you had 3,3v on Q9701 pin3 which is directly connected to R9705

To find out why there is 3.3v on OV_VLT I would check the points I placed arrows, I do suspect (circled) If D9608 shorted it would provide the D3.3v to the OV_VLT line OR one of those voltages is too high and causing its zener to conduct.

Attached Files

**berrmich** · 08-25-2023, 08:19 PM

Re: Sharp LC-C4655U Flashing OPC and Power lights.

Just checked again with CH/Vol. Yes your absolutely right. 3.3 on one side and 0.7 on the other. Sorry about that.

What's next?

**R_J** · 08-25-2023, 08:39 PM