Samsung UE46EH6030 - Blowing fuse and mosfet

[tn245]

Anybody worked on this power supply? PSU is PD46CV1_CSM (BN44-00552A). Came to me with blown primary fuse. I found ICM801 - FSFR1700XS had a hole in the side, QP801S 13NM60N mosfet shorted drain-source, QM801 PMBT2907A smd pnp transistor shorted collector-emitter.

I replaced the above mentioned components. Powered up the board with 60W bulb in series to limit current. Bulb lit then went dim. 5v and 3.3v ps_on/off present. Tried to power up without lightbulb and something flashed around ICM801. Fuse blown, mosfet shorted again. pnp transistor seems ok. No hole or shorts in ICM801 but don't know if it's ok.

There is a repair kit for this board but it seems to be a general one for all potential problems with more parts than I need. I don't have the other two fuses open or large diodes shorted but potentially the other two ics ICS801 and ICP801S could be the culprits. Not sure what the smd diode is in the kit.
http://www.ebay.com/itm/Samsung-BN44...-/361740963020

Anybody encountered this one before or have any thoughts or ideas for fault finding?

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

So I'm going to replace ICS801 (D2011K) and ICP801S (SPC7011F) as well as the previously replaced parts.

[ReeceyBurger123]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Id also advise you change ICM803-smd pfc controller.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

ICP801S is that smd pfc controller. ICM803 is a 3-pin zener diode.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

So I got the parts finally and put them in. I'm running the board with a 100W bulb in series. LED backlight strings flash rapidly. PFC cap is at 260V.

The PFC controller ic is getting 14.5V Vcc. The other pins are at:
1 FB: 1.6V
2 COMP: 5V
3 RT: 1V
4 OVP: 1.9V
5 IS: -0.02V
6 GND
7 OUT: 14.8V (I guess this is pulsing but my meter is reading it as DC? Does fluctuate slightly)
8 Vcc: 14.5V

Datasheet for pfc ic:


I've been referencing the attached schematic although it is not the same board it has some similarities and is the closest I could find.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Actually the pfc circuit seems to be working. I noticed the Vcc to the FSFR1700 was low and fluctuating, so removed the jumper supplying Vcc to it and now the pfc cap gets to 390V. So something in the FSFR circuit is causing the trouble.

[dick_barton]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

I know you say the schematics are not identical but is there a zener similar to ZDM810 which could be shorting/loading the 15V supply

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Yes it does have ZDM810 in the same position. In fact I have just now been experimenting with applying voltage to the Vcc input with that zener in and out of circuit and it does appear to be dropping the supply voltage a bit. Vcc needs to be at least 12.5V for operation and it's sitting around 8V. I will see if I have another zener I can put in there and test with.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Hmm. I don't think it's the zener. I put in an 18V zener which I had and the voltage still bounces around 8V. I removed the FSFR ic completely to see what Vcc is with it out of the equation and it is a steady 13V. CM812 capacitor is measuring 2 ohms ESR. I'm sure that could be an issue but I don't have a 10uF 50V cap at the moment to replace with. Have to come back to this tomorrow.

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Are you still testing the board with 100W lamp in the circuit and DCV on the main cap is at only 260 VDC?What are the DCV on caps CS805, 811 in that STBY power supply section?

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Yes, still have the 100W lamp in circuit. I'm afraid to take it out as last time I blew the mosfet again. That was before pfc ic replacement though. 260V on the main cap. As I mentioned it gets 390V if the FSFR1700 part of the circuit is disconnected so pfc seems good.

CS805 is 15.3V and CS811 12.6V both fluctuating a bit around those values. (that's with everything connected in and lamp in series)

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Yes, still have the 100W lamp in circuit. I'm afraid to take it out as last time I blew the mosfet again. That was before pfc ic replacement though. 260V on the main cap. As I mentioned it gets 390V if the FSFR1700 part of the circuit is disconnected so pfc seems good.

CS805 is 15.3V and CS811 12.6V both fluctuating a bit around those values. (that's with everything connected in and lamp in series)

Those Voltage on the caps should be higher than that, I expect around 18VDC.
That Voltage is fed to a switched Transistor to supply the VCC to run the other SMPS circuit and the PFC IC so the Voltage may be low due to 260VDC instead of 330 Vdc in standby mode.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Those readings were all when power supply and backlight circuit were switched on. The psu is set up to switch on if not connected to main board and the TV obviously died when so the main board is switching it straight on. Anyway I put a resistor between ps on and gnd and now in standby mode I have 320V on the main cap, CS805 is 19.5V and CS811 is 11.5V.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

CS811 voltage is the Vcc for the standby ic which should be 11V according to the schematic for similar psu I attached.

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

Those readings were all when power supply and backlight circuit were switched on. The psu is set up to switch on if not connected to main board and the TV obviously died when so the main board is switching it straight on. Anyway I put a resistor between ps on and gnd and now in standby mode I have 320V on the main cap, CS805 is 19.5V and CS811 is 11.5V.

So now you do have 19.5V on the C805 without 100W lamp in place?

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

BTW, so now without the lamp and no connection to the main board, all the Voltages and the backlights are on?

[tn245]

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.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

I haven't tried it yet without the lamp with psu fully on as I want to make sure it's not going to blow the mosfet and other ics again. The lamp is glowing medium brightness when out of standby mode. Is the lamp maybe just what is causing the low Vcc to the FSFR1700 and actually everything is ok? Should I try without?

[budm]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

That 18V (or 19V) is regulated down by the linear regulator circuit (transistor and zener diode) to feed the ICs.

[tn245]

Re: Samsung UE46EH6030 - Blowing fuse and mosfet

That 18V (or 19V) is regulated down by the linear regulator circuit (transistor and zener diode) to feed the ICs.

That was my understanding, and ICP801S pfc ic (SPC7011) is getting it's 15V Vcc fine, but the FSFR1700 only has ~8V on Vcc pin.