Samsung UN46D6050 No power, blinking led twice

[Gizzmo_jr]

Model: Samsung UN46D6050TFXZC
Version: H301
Mfg Date: October 2011
SMPS: BN44-00423a
Board Front Pic
Board Rear Pic

Ok I need help!

Background;
Watching TV few nights ago, 2min left in my show of course, and TV goes black. Remote won't turn it on, power cycle no luck, nothing.
Power LED flashes twice, five times then pause and repeat. (Why have blink codes if they're not useful?)

I recalled Samsung doesn't have a great reputation for capacitors, so first thought was check for any that were popped. I saw one slight bulging, and another that was questionable, so replaced them both. No change.
I'm not a hobbyist for repairs, but I'm more then comfortable doing this kind of repair. So off to Google!!!

So that's how I found this forum with it's dedicated members and loads of information.
Doing some searching, I found this;
Fast Track Guide

Did the backlight test, no backlight. My DMM didn't have a capacitor test mode, so I decided I wanted to see if I could fix this myself, I bought a new fancy DMM for my workbench and kept inspecting the board. Ends up the replaced caps were fine?!

What I've Done;
There's no signs of cold soldier joints, anything blown or discoloured. Fuses are fine.
Found a repair kit, so I'm using that as a means to start troubleshooting.
Managed to find the schematic, although some notes are in Spanish.

RM807 is fine.
Both transistors passes a simple diode test.
Bridge rectifier passes a simple continuity test. Gets warm while board is plugged in.

Board Tests
CP814S - 393v
CM813 - 22uF
CNM803a
p16 - PWR ON/OFF - v3.3
p15 - B5V - 0v
p14 - A5V - 5.31v
p13 - B5V - 0v
p9 - Vamp - 10-25mV
p8 - BLE_ON - 0v
p7 - Vamp - 15-35mV
p5 - B13V - 0v
p3 - B13V - 0v

So I have standby power at least!
I went on to test the other ICs from the repair kit but wasn't getting any source voltages that would turn them on.
The FET that would provide 5VB, no voltage reading at CM875. Figured it wasn't getting the input 13v.
No 13v reading from CM858 or CM859 (both caps good), so the winding from the transformer isn't giving output.

This is where you come in;
I feel like the power transformer isn't working, but the labels aren't helping to find a schematic breakdown, or even a replacement order part.

If there's more that I can troubleshoot, I'm all ears.
I borrowed the bedroom TV, and I'm only in the hole for some caps and a DMM (but I don't count that). I'm having fun troubleshooting, but definitely not opposed to clicking "Buy Now" off eBay if it isn't fixed in the next week or two. My heart tells me I'm $5 and a Digikey order away from fixing this! May consider a "finders fee" too

-Matt

[Caleb]

Re: Samsung UN46D6050 No power, blinking led twice

it sounds like you are well on your way to fixing your set, I located the power supply schematic and a service manual for a very similar model, I couldnt find that exact model. Hope this will help you along.

[budm]

Re: Samsung UN46D6050 No power, blinking led twice

What is the P/N of the SMPS IC ICM801?
Right now the PFC and STBY power supply is working otherwise you will not have that 395VDC boosted Voltage.
Cap CM813 tested OK?

[Gizzmo_jr]

Re: Samsung UN46D6050 No power, blinking led twice

it sounds like you are well on your way to fixing your set, I located the power supply schematic and a service manual for a very similar model, I couldn't find that exact model. Hope this will help you along.

Woah that schematic has annotations and much better info, thanks!
That troubleshooting doc is awesome, this is why I ask the pro's here

What is the P/N of the SMPS IC ICM801?
Right now the PFC and STBY power supply is working otherwise you will not have that 395VDC boosted Voltage.
Cap CM813 tested OK?

ICM801 from searching around here (trying to avoid removing everything to see the label) should be a FSFR-1700XSL

Cap CM813 tested good. I was curious about it once my eyes were focused on the transformer. Tested with one leg desoldered.
22nF or uF, can't recall what the range was on the DMM.

[budm]

Re: Samsung UN46D6050 No power, blinking led twice

It is 0.022uF DC blocker/coupling cap for driving the primary winding of the transformer, the IC is the half-bridge drive setup.
I am not going to assume that the IC is FSFR-1700XSL or not since we need to verify the DCV reading on the legs of the IC based on the IC P/N, so if the IC is not the right one then it will be a waste of time.
Per spec sheet of FSFR-1700XSL, pin 7 is the VCC pin so verify the DCV and the connection of that pin 7 to see if it matches the spec sheet of the FSFR-1700XSL.

[Gizzmo_jr]

Re: Samsung UN46D6050 No power, blinking led twice

It is 0.022uF DC blocker/coupling cap for driving the primary winding of the transformer, the IC is the half-bridge drive setup.
I am not going to assume that the IC is FSFR-1700XSL or not since we need to verify the DCV reading on the legs of the IC based on the IC P/N, so if the IC is not the right one then it will be a waste of time.

You are correct, not to assume anything. Here is where I got that P/N from. (See attached file)

[budm]

Re: Samsung UN46D6050 No power, blinking led twice

OK, check the DCV on VCC pin 7 to see what you have.
the LVCC (pin 7) Voltage has to reach 12.5V (typical) for the startup Voltage.

[budm]

Re: Samsung UN46D6050 No power, blinking led twice

BTW, I look at the diagram again and the spec of the IC, pin 8 is trimmed of so there is no connection to pin 8 but the service diagram show pin 8 has connection to it.
That diagram looks to be reverse engineered by someone so I do not believe it is correct.
Pin 10 (VCTR) is the output pin per spec sheet, the diagram is shown as pin 9, so it is wrong in the diagram.
Pin 9 of the spec sheet is HVCC pin, the diagram is shown as pin 8, so it is wrong in the diagram.

[Gizzmo_jr]

Re: Samsung UN46D6050 No power, blinking led twice

I'm absolutely beaming from the knowledge coming from you guys!

I'll toss that (wrong!) schematic I was using. Once I get home I'll get the values and the IC P/N.

[budm]

Re: Samsung UN46D6050 No power, blinking led twice

I would at least check pin 7 LVCC pin (make sure to count the pin correctly) just to see first before removing the heatsink, Black probe of the meter will be on the negative leg of the main filter cap CP814S which is the GND ref for the Primary DC side of the circuit, do not use chassis GND for the meter, and be real careful since you are working in the HOT DEADLY side of the circuit.
To remove the heatsink, you will need 60W iron with wide tip and use flux and add more solder to the heatsink mounting legs.

[Gizzmo_jr]

Re: Samsung UN46D6050 No power, blinking led twice

OK, check the DCV on VCC pin 7 to see what you have.
the LVCC (pin 7) Voltage has to reach 12.5V (typical) for the startup Voltage.

Well ain't that a thing, it only reaches 12.4 VDC. Proceeding to getting the item off the board now.

[Gizzmo_jr]

Re: Samsung UN46D6050 No power, blinking led twice

Surprise! I was able to see between the heatsink and the IC, and sure enough...
Fairchild FSFR1700XSL (B39ED also marked)

The other schematic has 14.2VDC as marked for the same pin. To whom created the schematic decided to ignore the NC pin 8 for some reason.

[budm]

Re: Samsung UN46D6050 No power, blinking led twice

The 12.5V is the typical value, per spec some IC may start running at as low as 11.2V, some may require as high as 13.8V.
So 12.4 should be enough, but check the DCV at the Emitter and at the Base of the Transistor QM801 Voltage regulator circuit against GND REF to see what you have.

[Gizzmo_jr]

Re: Samsung UN46D6050 No power, blinking led twice

Base ~11.5-12
Emitter ~12,5
Collector ~12.5

But it seems like it pulses, they all go up an additional 2DCV then back down to what I just listed.

Fun fact, the backside PCB lists Pin10 of the half bridge as Pin9, dumb.

[Gizzmo_jr]

Re: Samsung UN46D6050 No power, blinking led twice

The 12.5V is the typical value, per spec some IC may start running at as low as 11.2V, some may require as high as 13.8V.
So 12.4 should be enough, but check the DCV at the Emitter and at the Base of the Transistor QM801 Voltage regulator circuit against GND REF to see what you have.

Done, values as per the above post from lastnight.
Went ahead and ordered ICM801 replacement and a transistor (just in case).

Called one of the local repair shops, found out they don't stock/sell components anymore and a quick chat over the phone with a service tech hinted they don't try fixes much, just go straight to ordering boards...shame.

[Gizzmo_jr]

Re: Samsung UN46D6050 No power, blinking led twice

What is the P/N of the SMPS IC ICM801?

Ha, you called it!

My replacement SMPS IC came in and I was probably too excited to get my TV back. Either my mind went blank as to which ground I was using, or something funky happened. When I checked the voltages at CNM803a, no change from before (5VB, 13v still 0v). Walked away and cut the grass.

Came back to troubleshoot, but something in my head said to reinstall the board and do a back-light test. It's alive!
Reconnected the main board, and got my logo and no video input ui.
Been watching Plex for over a hour. Makes me wonder if main board connection has a 'feedback' voltage to enable the rest of the circuit. Ether way, I'm happy.

budm, thank you so much.