Sharp LC-60SQ15U TV DPS-167CP - No power

[R_J]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

I no longer know what to do, maybe IC7903 is defective ? I also read on another forum that the voltage on large caps should be 380V with a working ic7801, and I have 300

You need the #$%%^ standby circuit working BEFORE the pfc circuit OR the main supply circuit will work.

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

I no longer know what to do, maybe IC7903 is defective ? I also read on another forum that the voltage on large caps should be 380V with a working ic7801, and I have 300

[R_J]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

C7900 is likely good, If it was open circuit it will not stop the circuit from working. This cap is not your problem.

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

What is your ohm reading on R7900?

R7900 is ok, I am writing about C7900

[dskall]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

What is your ohm reading on R7900?

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

and I also suspect the C7900, but I don’t understand how to check it with a multimeter. Like a regular cap, it does not show voltage after charging.

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

If the optocoupler and the diode are good, then it only leaves the ic that is bad.
If you look at the datasheet page 11, you will see that without anything connected to the FB pin, that pin should be at 7 volts. Normally the optocoupler controls this voltage and varies it around 3~4 volts to control the ic. You measured almost 0 volts on the FB pin. So something is keeping the voltage low or the ic is bad.

is it possible to check ic somehow? in my city they are only in one store, it will be from the same batch.

How i can check my ic? Thanks

[R_J]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

If the optocoupler and the diode are good, then it only leaves the ic that is bad.
If you look at the datasheet page 11, you will see that without anything connected to the FB pin, that pin should be at 7 volts. Normally the optocoupler controls this voltage and varies it around 3~4 volts to control the ic. You measured almost 0 volts on the FB pin. So something is keeping the voltage low or the ic is bad.

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

I checked diode D7908 57Omh and infinity , PC7904, PC7903 desolder and check all fine(

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

What is PC7904 ? And which diode should be soldered to test?

PC7904 i found, how check his?

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

I would check the resistance and compare with the other two or try exchanging it with pc7904 and see if you get your standby voltage.
You should be able to leave the zener diode out of circuit for testing.

What is PC7904 ? And which diode should be soldered to test?

[R_J]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

Ok, i check later (it's too late, I'm going to sleep). How i can check IC7903 defective or not?

I would check the resistance and compare with the other two or try exchanging it with pc7904 and see if you get your standby voltage.
You should be able to leave the zener diode out of circuit for testing.

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

I think something is causing the voltage to be too low. If you look at the datasheet for the ic (page 11) you will see FB/OLP pin is supplied by approximately 7 volts, this line is controlled externally, so I suspect either the diode D7908 is bad or the optocoupler is bad.
170Ω and 90Ω does seem to be low. lift one end of the diode and check again to see what the resistance is.

Ok, i check later (it's too late, I'm going to sleep). How i can check IC7903 defective or not?

[R_J]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

What do you think?

I think something is causing the voltage to be too low. If you look at the datasheet for the ic (page 11) you will see FB/OLP pin is supplied by approximately 7 volts, this line is controlled externally, so I suspect either the diode D7908 is bad or the optocoupler is bad.
170Ω and 90Ω does seem to be low. lift one end of the diode and check again to see what the resistance is.

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

What do you think?

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

Check for a shorted D7988, or defective PC7903, something is killing the feedback voltage. I suspect the voltage needs to be above 1 volt and maybe around 3~5 volts, but needs to be lower than 8 volts

D7908 170 and 90 Omh

[R_J]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

7907 check his ok, on 4 legs 40mV

Check for a shorted D7988, or defective PC7903, something is killing the feedback voltage. I suspect the voltage needs to be above 1 volt and maybe around 3~5 volts, but needs to be lower than 8 volts

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

What is the voltage on pin 4 of ic7903, this is the FB (feedback) voltage.
Is R7907 ok?
IC7801 will not effect ic7903. IC7801 is the pfc driver ic. and is not active in standby

7907 check his ok, on 4 legs 40mV

[R_J]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

What is the voltage on pin 4 of ic7903, this is the FB (feedback) voltage.
Is R7907 ok?
IC7801 will not effect ic7903. IC7801 is the pfc driver ic. and is not active in standby

[romasik]

Re: Sharp LC-60SQ15U TV DPS-167CP - No power

If all components off of pin5 are good. May have bad ic.

So I replaced it with a new one.

My friend advises me to change IC7801, but I don't understand how it can affect IC7903