Samsung UN46C6400RFXZA audio but no picture (pics incl).

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

Thank you, I was just googling for that.

Does this rule out that something else is not going on in the other two boards?

Should I replace ICD1, or is there any other testing I should do?

[budm]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

Right now you have problem on the T-CON board, I would start checking the Voltages around that IC to see if it has VCC to run it or not and see if it has 12Vin to feed that AVDD boost converter circuit or not, and also check the resistance of MLCC aorund that circuit to see if any of them show low resistance reading or not, or if the working T-CON is not expensive then you can try that too. You have spec. sheet of the IC now so that should help.

[nomoresonys]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

One there for 18 bucks. https://www.ebay.com/itm/BN81-04159A...frcectupt=true

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

Right now you have problem on the T-CON board, I would start checking the Voltages around that IC to see if it has VCC to run it or not and see if it has 12Vin to feed that AVDD boost converter circuit or not, and also check the resistance of MLCC aorund that circuit to see if any of them show low resistance reading or not, or if the working T-CON is not expensive then you can try that too. You have spec. sheet of the IC now so that should help.

So, I've traced all components attached to each pin on ICD1/MAX17122, measured the resistance of every cap and resistor, and then voltages. All caps directly connected to a chip pin were in the 500-750 Ohm range.

I can type all the measurements up, but here is the jest of it:

[B]PIN	NAME	MEASURED[/B]
2	IN	12.65V
3,4	IN2	12.65V
6,7	LX2	2.45 - 2.6V
23	DEL	3.8 - 4.8V
30	LX3	0V
31	IN3	12.65V
35	VL	5v
37,38	LX1	4-5mV

Of course because of the low LX1, the diode D6 sees nothing so AVDD is very low. Is it safe to conclude that there is some internal damage on the chip?

BTW, I think there is a mistake (typo?) on p 18 of the MAX17122 application sheet. The top right of the functional diagram graphic should probably say 'step-up'.

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

And would it make sense to try to apply 15V (and gradually up to 20V) from an external source to see if that does anything? I'd rather not risk more damage to the board.

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

One there for 18 bucks. https://www.ebay.com/itm/BN81-04159A...frcectupt=true

Thank you for the link.

I cross-referenced with shopjimmy it is a listed substitute part # and ordered it.

Should be here next week. I'll report back with results.

EDIT: thank you to everyone for your help. I am learning a lot.

[nomoresonys]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

Ok, worth a shot, I look at like if you spend 5 hours trying to find out exactly which component went bad can be a real pain if you get a good one you can eliminate it and move on to something else and you have a spare if you ever need it.

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

Can I apply 15V from an external supply to the AVDD test point on the defective board?

[nomoresonys]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

They say never apply more than the rating.

[budm]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

https://www.badcaps.net/forum/attach...6&d=1549995881
What is the P/N of ICD2 switched MOSFET which is used the same way as Q1 as shown in the spec sheet page 18 (application schematic) and is is driven by Gate pin 1 of the MAX17122.
If Q1 is not turned on then there will be no 12v feeding the AVDD boost converter circuit (L6, D6, LX1 pins).
So report the P/N of ICD2, Voltage reading on each pin of the ICD2. It can be bad ICD2.
You can use the application circuit as the guide.

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

ICD2 is 58AD, and after startup, the pins below and above the 'D' (pins 3, 4?) are 12.64 volts.

I didn't take any startup voltages.

I didn't report that before, but touching GATE to take a voltage reading while the TV is on causes it to shut off. If I probe that pin and then turn on the TV, it will stay on and shows 12.64V. Is this due to my cheap DMM adding resistance to the circuit?

Also, there are no pins labelled L6, and D6 on the 17122.

[budm]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

L6 is the inductor (100 printed on top) with L6 designator.
D6 is the Diode D6.

ICD2 Pin 1 is marked by white triangle.
ICD2 Pin 3 is the GATE pin, it should change state when TV is turned on and off.
ICD2 Pin 4 is fed by 12V from the fuse.
ICD2 Pin 5, 6 are the 12V out.
So I need to know what Voltage are for each one of those pins.

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

L6 is the inductor (100 printed on top) with L6 designator.
D6 is the Diode D6.

Pin 1 of the IC is marked by white triangle.
ICD2 Pin 3 is the GATE pin.
ICD2 Pin 4 is fed by 12V from the fuse.
ICD2 Pin 5, 6 are the 12V out.
So I need to know what Voltage are for each one of those pins.

ICD2 Pin 1 is 0
ICD2 Pin 2 is 0
ICD2 Pin 3 is 12.64
ICD2 Pin 4 is 12.64
ICD2 Pin 5 is 0
ICD2 Pin 6 is 0

Is this the data sheet for ICD2?
https://cdn.badcaps-static.com/pdfs/...68fe1b9704.pdf

[budm]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

Well the GATE pin of the 58A MOSFET should go LO for it to be on but the Max17122 is not pulling that pin low.

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

Update:

I replaced the T-CON with a used one of unknown condition, and it now has a picture, but it is distorted. Sound is OK, antenna and all HDMI ports work but picture is distorted on all input sources. I did a service mode factory reset. The distortion constantly shifts around and is not specific to any part of the screen.

[nomoresonys]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

May have gotten a faulty tcon, try gently cleaning and reseating ribbons and lvds cable, could try service menu adjustment. Be careful in service mode, always make note of setting before trying adjustment so you can put it back if needed. Look for lvds format or similar, try adjusting that, might clear it up, can also check those test points on replacement tcon, see if they have the proper voltage.

[DXseekerMO]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

Yes, check the LVDS cable especially. I've seen this before in a Vizio with a loused up LVDS.

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

I checked LVDS cable ends, and their connectors. They all look good. Tomorrow I'll try cleaning everything with alcohol, and reseating.

I checked all the voltages on the new T-CON board -- here are some relevant ones:

VIN	 12.48
AVDD	 17.10
VCC12	 1.22
VCC33	 3.27
VOFFE	-13.33
VSS	 -7.45
VONE	 28.00
VR	 8.45
VCOMS1	 6.92
VCOMS2	 6.84
VCOMS3	 6.92
VCOMS4	 6.92
VCOMG1	 6.84
VCOMG2L	 7.04
VCOMG3	 6.97
VCOMG2R	 6.97

I'll look at the service mode settings for LVDS tomorrow. I'll record everything before changing it, but if anyone has any pointers in the meantime, I'd appreciate it.

I also upgraded the firmware to the latest (via wired ethernet).

[GLInick]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

I cleaned the LVDS cable and connectors with alcohol and sure enough the picture is back to normal again.

A big thank you to all who helped.

[budwich]

Re: Samsung UN46C6400RFXZA audio but no picture (pics incl).

good work... you now have some working "bench marks" for the voltages involved... if you have more spare time, you could continue troubleshooting the "old card" and perhaps fix it as a spare or otherwise. Further, you probably don't even need voltages as unpowered resistance measurements / comparisons at strategic point will probably high light the area of interest / repair. Always good to see a working outcome.