No Stdby Light Samsung Ue46d5000

[Fritz23]

Hey guys,

I currently have a Samsung UE46D5000 which shows no reaction at all. There's no Standby light and no clicking noise. Already replaced the PSU, because the old one seemed faulty (no STDBY voltage, no other voltages), but it didn't change much.

With the old PSU and disconnected mainboard the backlight did flash on and off. With the new (used) PSU and disconnected mainboard the backlight stays on.

When I connect the mainboard the backlight turns off and the TV seems to be shut off.

I tried to jumper the PSU (PS_On and A5V, which seemed to be 5V_SB), but this killed a small Transistor. The PSU still works.

I found a damaged double Z-Diode (for the CI) on the mainboard and soldered it out.

When everything was reassembled I checked the voltages again. The PSU seems to start and delivers all the Voltages correctly to the mainboard, but the IR/Button-board doesn't get any Voltage. It should have 5V(A5V) but instead this pin is shorted to ground. Í guess it shouldn't be shorted.

Any ideas where to search the fault? I was not able to follow the traces of A5V from PSU to A5V IR board. They have no direct connection.

[Fritz23]

Re: No Stdby Light Samsung Ue46d5000

*push*

[ben7]

Re: No Stdby Light Samsung Ue46d5000

Hey guys,

I currently have a Samsung UE46D5000 which shows no reaction at all. There's no Standby light and no clicking noise. Already replaced the PSU, because the old one seemed faulty (no STDBY voltage, no other voltages), but it didn't change much.

With the old PSU and disconnected mainboard the backlight did flash on and off. With the new (used) PSU and disconnected mainboard the backlight stays on.

When I connect the mainboard the backlight turns off and the TV seems to be shut off.

I tried to jumper the PSU (PS_On and A5V, which seemed to be 5V_SB), but this killed a small Transistor. The PSU still works.

I found a damaged double Z-Diode (for the CI) on the mainboard and soldered it out.

When everything was reassembled I checked the voltages again. The PSU seems to start and delivers all the Voltages correctly to the mainboard, but the IR/Button-board doesn't get any Voltage. It should have 5V(A5V) but instead this pin is shorted to ground. Í guess it shouldn't be shorted.

Any ideas where to search the fault? I was not able to follow the traces of A5V from PSU to A5V IR board. They have no direct connection.

Is the A5V pin on the IR/button-board still shorted out when the PCB is disconnected from the mainboard? If it is, the short is on the IR/button-board. If the mainboard has a short, then you can start checking the voltage regulators to find any that have a short. You can remove the regulator to see if it indeed is the regulator that is bad. If it's not bad, then the most likely thing would either be a shorted out IC or a shorted out ceramic capacitor.

-Ben

[Fritz23]

Re: No Stdby Light Samsung Ue46d5000

Hi there,

I ended up buying a new mainboard for 25€, which solved the problem in combination with the new power supply.

Anyways one year later I have the same TV with the same problem again. Still not even a standby light.

I unmounted the power supply and am testing it on my table. Without anything connected it just makes a silent clicking noise every second. While trying to find a 5V standby line I just saw, that every voltage is jumping around between 0V to ~18V. Even the Power On/Off line jumps between 1.5V and 3V.

I attached a diagram of the A5V line.

There are no bulging caps and the main cap is charged to 385V. Checked both fuses.

I'm quite surprised by this behavior and don't know what to do.

[budm]

Re: No Stdby Light Samsung Ue46d5000

Check the resistance between GND and the A5V pin to see what you get.
Pictures provided by shopjimmy.

[Fritz23]

Re: No Stdby Light Samsung Ue46d5000

GND-A5V -> Around 7 MOhm, but dropping while measuring.

I did find the schematic online: BN44-00473A schematic

[ReeceyBurger123]

Re: No Stdby Light Samsung Ue46d5000

Common issue with these is shorted Cpu and failed bga solder on the Cpu due to poor heatsinking.

[budm]

Re: No Stdby Light Samsung Ue46d5000

GND-A5V -> Around 7 MOhm, but dropping while measuring.

I did find the schematic online: BN44-00473A schematic

OK, so the output side does not have shorts (no other boards connected to the power supply board at this point), the circuit ticking usually indicates shorts in the output side or bad startup/running caps or some thing is overloading the circuits and cause it to be in startup/shutdown cycle, next you should check the caps CS802, 805 ESR, you can also try heating them with hair dryer to see if the STBY A5V will become steady or just replace the caps.
BTW, check the resistance between the two legs of cap cp804.

[Fritz23]

Re: No Stdby Light Samsung Ue46d5000

OK, so the output side does not have shorts (no other boards connected to the power supply board at this point), the circuit ticking usually indicates shorts in the output side or bad startup/running caps or some thing is overloading the circuits and cause it to be in startup/shutdown cycle, next you should check the caps CS802, 805 ESR, you can also try heating them with hair dryer to see if the STBY A5V will become steady or just replace the caps.
BTW, check the resistance between the two legs of cap cp804.

I currently don't have an ESR meter. Heating these caps didn't change anything.

I couldn't find a CP804. In the schematic it says CP804 is "N.C.". I measured the resistance between PFC-VCC and P-GND but it's too high to measure (over 20 Mohm)

Common issue with these is shorted Cpu and failed bga solder on the Cpu due to poor heatsinking.

Is there any way to check this?

[budm]

Re: No Stdby Light Samsung Ue46d5000

I currently don't have an ESR meter. Heating these caps didn't change anything.

I couldn't find a CP804. In the schematic it says CP804 is "N.C.". I measured the resistance between PFC-VCC and P-GND but it's too high to measure (over 20 Mohm)



Is there any way to check this?

I have you check the resistance where the CP804 is even though it is not installed is to find out if the PFC IC Vcc pin show low resistance or not, and it is not.

[budm]

Re: No Stdby Light Samsung Ue46d5000

Connect 100 Ohms resistor between the PS-ON pin and GND pin (this will turn off the PFC circuit), do the same to the BL-ON (BLU ON) pin and see if the A5V will be stable or not.

[Fritz23]

Re: No Stdby Light Samsung Ue46d5000

I have you check the resistance where the CP804 is even though it is not installed is to find out if the PFC IC Vcc pin show low resistance or not, and it is not.

Ok, so this IC is good, right?

Connect 100 Ohms resistor between the PS-ON pin and GND pin (this will turn off the PFC circuit), do the same to the BL-ON (BLU ON) pin and see if the A5V will be stable or not.

With 100 Ohms between PS-ON and GND A5V is stable at 5.26V. With 100 Ohms between BL-ON and GND A5V is still stable at 5.26V.

[budm]

Re: No Stdby Light Samsung Ue46d5000

Ok, so this IC is good, right?



With 100 Ohms between PS-ON and GND A5V is stable at 5.26V. With 100 Ohms between BL-ON and GND A5V is still stable at 5.26V.

OK, we are getting some where.
Now check the resistance between GND and the Collector of the switched/Linear regulator transistor QM801 (This transistor supplies the VCC to run the ICM801) to see if it shows low resistance.

[Fritz23]

Re: No Stdby Light Samsung Ue46d5000

Collector of QM801 to P-GND shows 3.46 kOhms in one way and 9.91 kOhms the other way.

[budm]

Re: No Stdby Light Samsung Ue46d5000

Is there any way you can disconnect the Collector so that Transistor will not be supplying the VCC to ICM801 and then you can remove the resistor between the PS-ON pin and the GND to see if the A5V will still be at 5V?

[Fritz23]

Re: No Stdby Light Samsung Ue46d5000

I disconnected the collector of QM801 (E and B still connected) and removed the 100 ohms resistor between PS-ON and GND. Resistor between BL-ON and GND stays.

A5V still stable at 5.26V.

[budm]

Re: No Stdby Light Samsung Ue46d5000

OK, What DCV do you have on the Collector?
Do you now get about 400VDC between the two legs of the main filter cap? It should since we now should have VCC feeding the PFC IC.
so it is something in the Backlights circuit, I suspect the ICM801 or the filter caps connected to the VCC pin of the ICM801.

[Fritz23]

Re: No Stdby Light Samsung Ue46d5000

I get 14.6 DCV on the collector.
Main cap is charged to 392 VDC.

It wouldn't be the first time that such an IC failed. Is there anything more to check to determine if it's the ICM801 or the caps (you mean the ceramic caps CM802, 803, 804, 805, 806, 809 and 813 or the electrolytic caps CM807, 812 and 814?)

[budm]

Re: No Stdby Light Samsung Ue46d5000

You can lift the VCC pin of the IC and then solder the collector back in place to see if the A5V will stay.

[Fritz23]

Re: No Stdby Light Samsung Ue46d5000

Lifted ICM801 Pin7-LVCC, reconnected collector of QM801 and removed 100 ohm resistor between BL-ON and GND. A5V still stable at 5.26V

I guess I have to order a new FSFR1700XSL now, right?

What exactly is the reason for this IC to fail? Since it's in the backlight circuit I suspect it has nothing to do with a shorted CPU or any other fault on the mainboard, right?