Samsung UE46EH6030 - Blowing fuse and mosfet

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

That was with the 100W in.

Just tried without it on standby mode and CS805 is 18.5V but voltage is creeping up. Was heading up to 19V when I decided to switch off.

That reversed engineer schematic has lots of errors, if you look at how the DCV is generated by the HIGHER AND LOWER Transformer windings, it is impossible to have lower Voltage on the HIGH winding than the low winding.
11V to run that STBY SMPS is right.

What is the P/N of the actual IC of the stby power supply? Really D2011K as shown in the diagram?

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Yup, so I've got all the right voltages in that part of the circuit. It's only in the FSFR1700 circuit I'm not getting the 15V Vcc.

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

You will have to find out what DCV you have on the E, B, and C of that transistor for the regulator circuit.
And you are saying you are getting 11VDC on the VCC of the stby ic?
See post 21.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Yes, 11V Vcc for the standby ic but that is in standby mode. It was 12.5V when out of standby.

Which transistor are you asking about? QS801, or QM801? Going by the bad schematic.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

So QM801 has about 14V on its base so must be switching off the Vcc supply to the FSFR1700. Just trying to get my head around how ICM803 shunt regulator works. It has 2.5V on Vref pin.

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

QS801
If the Base has 14V then the output will be 14V - Vbe of the transistor (about 0.6V) so the out put should be 13.4 VDC.
But per Schematic you have 15V zener in series with diode so the Base Voltage should be around 15.6 V (depend on the tolerance of the Zener diode) to get 15VDC output.
I expect the Collector Voltage to be around 18V or so. What is the Collector Voltage?

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

So what is the P/N of the STBY IC?

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Sorry I was testing QM801 there, not QS801. The numbers are confusing. QM801 is a pnp transistor switching Vcc supply to the FSFR1700. As it is a pnp the 14V on the base would be pretty much switching off the Vcc supply at that point right?

To answer your questions QS801 has ~15V on all pins. Standby ic is D2011K.

Standby circuit all seems to be fine. Any reason you are asking about that part of the circuit as the 15V Vcc supply from there seems fine? 15V is just not getting to the FSFR1700 ic.

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

QM801 Voltage of all 3 pins are???
ICM803 is used as protector to shut off QM801 if the PFC Boost Voltage is wrong.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

QM801:
B: 14V
E: 14.3V
C: 8V

All are fluctuating a little, especially collector.

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

QM801:
B: 14V
E: 14.3V
C: 8V

All are fluctuating a little, especially collector.

That transistor is not really turned on, you only have 14.3V (B) - 14V (E) = 0.3V Vbe Voltage.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Sure, makes sense since the PFC voltage is low I guess. So question is what is causing PFC voltage to be low? As I mentioned if I remove 15V Vcc link to FSFR1700 circuit PFC voltage is correct 390V , so either something in that circuit or could it be something on the secondary side? Need to study the datasheet for the FSFR1700 ic and measure its pins I guess. Will have to come back to it another time as my attention is required elsewhere now. Thanks for the input budm.

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

I think you need to check the PFC output Voltage sensing 1M resistors RP824, 826, 826, 827, 828, 829 (30K), and the DCV of RP829.
right now that ICM803 is not fully on to give bias current to turn on QM801, if you connect 1K resistor between Anode and Cathode of ICM803, you will probably get the VCC to run FSFR IC.

[Davi.p]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Your model is a 69W (i think at max, data took from a site's specs), 100w lamp is too much, replace with the 60w one, then retry the psu with some dummy loads or the mainboard..

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Thanks. I have switched to 60W bulb. Same thing happening although I am still testing with the panel leds as not sure what I would use as a dummy load. Budm all those resistors check out fine and DCV of RP829 is 1.9V.

Again if I cut Vcc supply entirely to the FSFR via J824 I get PFC 390V and DCV of RP829 is 2.5V so PFC output sensing is ok.

Seems that as soon as the FSFR gets Vcc supply the PFC drops which then means its Vcc is cut by ICM803/QM801. Just need to discover why PFC drops when the FSFR is activated.

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

"Again if I cut Vcc supply entirely to the FSFR via J824 I get PFC 390V and DCV of RP829 is 2.5V so PFC output sensing is ok." But you are using the extrenal powwer supply to supply the VCC, correct,
So QM801 Collector (output) is no longer connect to VCC pin when the jumper is removed, right?
We already know that the QM801 is not being turned on properly due to E-B Voltage, so did you you try using the resistor as I suggest in post 33?
That QM8001 has to be properly bias for it to provide correct VCC to run the IC, IC is not the problem, its the QM801 not being properly bias.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Not using external power supply. PSU is plugged into mains with lamp in series. With jumper J824 removed main cap is at 390V and QM801 collector is at 15V. So when not connected to VCC pin of FSFR QM801 is properly biased.

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Right now QM801 is not bias on because it thinks the PFC Voltage is wrong, like I said did you try using the resistor to force on QM801?
So if the QM801 is force on but still not putting out 14V.
BTW
B: 14V
E: 14.3V
C: 8V

How do you get OUTPUT of 15V when the input to the Emitter is only 14.3V?

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Sorry, I meant 14V (roughly) - just got home and was typing in a rush. My point is that if that jumper is removed, PFC is 390V and QM801 is bias and outputting enough VCC for FSFR.

But..

If the jumper is connected, PFC is 260V, in which case it makes sense that QM801 would not be bias

So my understanding of this is that the PFC and QM801 parts are operating correctly, but as soon as the FSFR tries to operate, PFC drops to 260V. (Thus cutting off its VCC supply via QM801).

Sorry if I am being dense. Not sure if we're totally talking cross purposes. I do appreciate you sticking with me on this.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Just for the sake of it tried the resistor to force on QM801 as suggested. FSFR LVcc (collector of QM801) is at just under 14V, fluctuating slightly. PFC main cap voltage now moves up and down between 100 and 130V.