Sharp LC-50P66U-completely dead PSU!!

[budm]

Re: Sharp LC-50P66U-completely dead PSU!!

What Voltage do you have on center pin of diode VD821 with ref to chassis gnd?
What Voltage do you have on center pin of diode VD820 with ref to chassis gnd?

[kgavionics]

Re: Sharp LC-50P66U-completely dead PSU!!

What Voltage do you have on center pin of diode VD821 with ref to chassis gnd?
What Voltage do you have on center pin of diode VD820 with ref to chassis gnd?

I didn't change anything, but somehow I got the 18.3 on the 16V rail, a fluctuating between 8.3 to 12.3V 12v rail, but no standby voltage!
When I press either on the power button or the on remote nothing happens the pin SW doesn't go high. I guess it's normal, because the main board needs the standby voltage to be present to work properly?

[budm]

Re: Sharp LC-50P66U-completely dead PSU!!

I didn't change anything, but somehow I got the 18.3 on the 16V rail, a fluctuating between 8.3 to 12.3V 12v rail, but no standby voltage!
When I press either on the power button or the on remote nothing happens the pin SW doesn't go high. I guess it's normal, because the main board needs the standby voltage to be present to work properly?

1) "I didn't change anything, but somehow I got the 18.3 on the 16V rail, a fluctuating between 8.3 to 12.3V 12v rail" so the 16V rail is steady at 18.3V, but the 12V rail is fluctuating between 8.3 to 12.3V?

2) What do you mean No Standby Voltage? The 12V and the 16V are the standby Voltage. STB pin is the PS-ON pin for receiving the power supply on control signal from the main board, it is NOT Standby power supply output pin.

3) SW pin the BL-ON pin for receiving the backlights circuit on signal from the main board.

4) PWM is the backlights dimming pin, it gets the control signal from the main board.

5) It has to be your measurement error for not getting the 16V and 12V at the connector in your earlier report because you cannot have PFC Boost Voltage and the 245V on LED connector if there are 0V on the 12V and 16V pins, it is impossible.

6) What happen to my post 21 Voltage readings request?

[kgavionics]

Re: Sharp LC-50P66U-completely dead PSU!!

hello Budm and thank you for your help it means so much to me!
I think it was my error for not getting the 16V and 12V!
Regarding, the voltage reading requested in #21 I was getting 18.3 and a fluctuating 12V.
Yesterday, I was contacted by the seller of the card, who is a TV repair technician. He's a super nice guy who offered me to help, he asked me to take the measurement across the backlight connector, which I did, I only was getting 1V or so! I removed the power for 15 min. After that I went to check the 12V and 16V, but I didn't have any of them. The booster voltage cap went down to 322V and I lost the 245V on backlight circuit!
I'm not sure what happened!! Now I removed the board again to check it off power!

[nomoresonys]

Re: Sharp LC-50P66U-completely dead PSU!!

So is the mainboard NOT sending the power on signal then?

[kgavionics]

Re: Sharp LC-50P66U-completely dead PSU!!

So is the mainboard NOT sending the power on signal then?

It looks like the mainboard, is not sending any signal back to the PSU.
By the way, this set is poorly designed and even though is branded SHARP, it's actually a Chinese crap made by Hisense!

[digitalscorpion]

Re: Sharp LC-50P66U-completely dead PSU!!

Did you have any luck with this?
I have similar power board with no output voltages.

[dick_barton]

Re: Sharp LC-50P66U-completely dead PSU!!

What voltages have you measured? Do they agree with those shown on the schematic in post #2

[digitalscorpion]

Re: Sharp LC-50P66U-completely dead PSU!!

What voltages have you measured? Do they agree with those shown on the schematic in post #2

I have no DC output voltages on connector XP903.
Nothing connected to power board currently, receiving no STB voltage, no 12v or 16v as well.

[dick_barton]

Re: Sharp LC-50P66U-completely dead PSU!!

Have you checked the wickman fuse F801 is not open circuit.
What DC voltage do you have when you measure across C870. Connect your meter probes to each leg of the capacitor.

[budm]

Re: Sharp LC-50P66U-completely dead PSU!!

Too bad OP never comes back with the follow-up.

[digitalscorpion]

Re: Sharp LC-50P66U-completely dead PSU!!

Have you checked the wickman fuse F801 is not open circuit.
What DC voltage do you have when you measure across C870. Connect your meter probes to each leg of the capacitor.

F801 is good.
C870 = 164V DC.

[dick_barton]

Re: Sharp LC-50P66U-completely dead PSU!!

The capacitor C815 which is connected to VCC (pin 8) of N801 should charge up to between 19 - 22V at switch on for the IC to start operating.

This capacitor is charged via VD801, VD802, R807, R808 abd R809 which you could check.

Next STB (standby) needs to be asserted. This can be accomplished by disconnecting the power supply from the mainboard and using 2 x 1.5V batteries connected in series to create a 3 volt supply. The negative lead of the battery to any ground pin of the power supply and positive lead of the battery connected to the power supply STB pin connection using a 1K resistor.

Then check the voltage again across C870

[digitalscorpion]

Re: Sharp LC-50P66U-completely dead PSU!!

The capacitor C815 which is connected to VCC (pin 8) of N801 should charge up to between 19 - 22V at switch on for the IC to start operating.

This capacitor is charged via VD801, VD802, R807, R808 abd R809 which you could check.

Next STB (standby) needs to be asserted. This can be accomplished by disconnecting the power supply from the mainboard and using 2 x 1.5V batteries connected in series to create a 3 volt supply. The negative lead of the battery to any ground pin of the power supply and positive lead of the battery connected to the power supply STB pin connection using a 1K resistor.

Then check the voltage again across C870

C815 = 0V
When you say assert the STB voltage, do you mean I should attempt to Insert 3v into it? Shouldn't the power supply board be producting that STB voltage?

[budm]

Re: Sharp LC-50P66U-completely dead PSU!!

C815 = 0V
When you say assert the STB voltage, do you mean I should attempt to Insert 3v into it? Shouldn't the power supply board be producting that STB voltage?

STB (Same as PS-ON) pin of this power supply board is the control signal Receiving pin that get the control signal from the main board to turn on the power supply, it is not Standby power supply output.
See my post #23 regarding to the pin names and what they are for.

[digitalscorpion]

Re: Sharp LC-50P66U-completely dead PSU!!

STB (Same as PS-ON) pin of this power supply board is the control signal Receiving pin that get the control signal from the main board to turn on the power supply, it is not Standby power supply output.
See my post #23 regarding to the pin names and what they are for.

Ohh. If no DC output to the main board, how does the main board provide control signal?
I will attempt the 3v insertion on STB line and report back. Thank you guys!

[budm]

Re: Sharp LC-50P66U-completely dead PSU!!

Ohh. If no DC output to the main board, how does the main board provide control signal?
I will attempt the 3v insertion on STB line and report back. Thank you guys!

I did not read your thread to find what you and Dick_Barton found so far, I am just pointing out what those pin names are.

[digitalscorpion]

Re: Sharp LC-50P66U-completely dead PSU!!

I did not your thread to find what you and Dick_Barton found so far, I am just pointing out what those pin names are.

I understand. i missed your #23 post with that detail.
I will now try to insert the 3v and take a measurement.

[dick_barton]

Re: Sharp LC-50P66U-completely dead PSU!!

Reading the information on the IDP2303 it appears to be a programmable IC so there is the possibility it may have been corrupted.

[digitalscorpion]

Re: Sharp LC-50P66U-completely dead PSU!!

The capacitor C815 which is connected to VCC (pin 8) of N801 should charge up to between 19 - 22V at switch on for the IC to start operating.

This capacitor is charged via VD801, VD802, R807, R808 abd R809 which you could check.

Next STB (standby) needs to be asserted. This can be accomplished by disconnecting the power supply from the mainboard and using 2 x 1.5V batteries connected in series to create a 3 volt supply. The negative lead of the battery to any ground pin of the power supply and positive lead of the battery connected to the power supply STB pin connection using a 1K resistor.

Then check the voltage again across C870

Applied 3v via method suggested. No change. C870 = ~168v DC. No other output voltages. At this point I will seek out a replacement power supply board. Thank you for the help.