Another Samsung Another Audio-But-No-Display Issue

[Michale32086]

I am beginning to think I have a SamSung curse.. Every time I touch one, it won't fix...

Samsung LN46C600....

At first I thought it was a plasma because it's A)Heavy and 2) Has metal back...

But, nope.. It's an LED/LCD...

I get sound, but no display... Read thru available LN46C600 threads...

https://www.badcaps.net/forum/search...archid=4308173

Strong flashlight shows display is present, so it's a backlight issue...

One post from BudM stood out...

BN44-00341B from TOM66. This board has pull-up resistors, so if you unplug the cable between power supply and the main board, the backlights should come on when you plug TV into the AC outlet.

On this set, I unplug the main board from the power board and plug in.. Don't get any kind of light, flicker or anything....

Before I tear into the unit down to the bare backlights, I was hoping there was something else I can check first...

In reading thru the afore mentioned threads, I read about the guy who invoked the wrath of Zues when checking the large caps...

Want to avoid that if at all possible..

T minus 5 days until my Rigol DS1074Z arrives

[CapLeaker]

Re: Another Samsung Another Audio-But-No-Display Issue

In reading thru the afore mentioned threads, I read about the guy who invoked the wrath of Zues when checking the large caps...

Want to avoid that if at all possible..

T minus 5 days until my Rigol DS1074Z arrives

For this I have something special. I took an clip lead, cut it in half and soldered it to a 5W 100 Ohm ceramic wire wound resistor. Put that on the caps, wait a few seconds and there shall be no more
Then I proceed with my LCR meter.

[budm]

Re: Another Samsung Another Audio-But-No-Display Issue

OK, without cable between the main board and the power supply board, check to see if you do have standby A5V, if you do then check and see if you do have >360VDC (you need to have this Voltage) on the main filter cap (check the DCV right at the two legs of the cap), if you do, then check the fuse FS802S.

[Michale32086]

Re: Another Samsung Another Audio-But-No-Display Issue

OK, without cable between the main board and the power supply board, check to see if you do have standby A5V, if you do then check and see if you do have >360VDC (you need to have this Voltage) on the main filter cap (check the DCV right at the two legs of the cap), if you do, then check the fuse FS802S.

FS802S checks out...

I do get 5v on the standby A5V when the cable between the main board and the power board is disconnected..

I am working up the courage to check the big 450V capacitor..

[budm]

Re: Another Samsung Another Audio-But-No-Display Issue

just do not touch anything with your hands or body, and do not let the probes slip out on you.

[Michale32086]

Re: Another Samsung Another Audio-But-No-Display Issue

just do not touch anything with your hands or body, and do not let the probes slip out on you.

That's my plan..

OK... With my son's help... After he finished laughing his arse at my skittish-ness....

393V +/-

[CapLeaker]

Re: Another Samsung Another Audio-But-No-Display Issue

get some alligator clips for those probes, problem solved!

[Michale32086]

Re: Another Samsung Another Audio-But-No-Display Issue

Yea, already ordered..

Nice Pomona clips with good insulation.. Checking voltages always scares me the crap...

Going into town tomorrow and picking up some generic ones to tide me over..

[budm]

Re: Another Samsung Another Audio-But-No-Display Issue

That's my plan..

OK... With my son's help... After he finished laughing his arse at my skittish-ness....

393V +/-

OK, PFC is working, now I need to look at the inverter circuit section next.

[Michale32086]

Re: Another Samsung Another Audio-But-No-Display Issue

OK, PFC is working, now I need to look at the inverter circuit section next.

OK,which section is that?? Looking at the schematic, I can't find that labeled..

[budm]

Re: Another Samsung Another Audio-But-No-Display Issue

OK, check CI818 capacitance, it is 0.47uF 450V Poly cap.

[Michale32086]

Re: Another Samsung Another Audio-But-No-Display Issue

OK, check CI818 capacitance, it is 0.47uF 450V Poly cap.

I assume that the arrow points to the Negative??

The access to the pads is somewhat limited... Is there any special trick to checking it??

[budm]

Re: Another Samsung Another Audio-But-No-Display Issue

It is non-polarized cap. You will have to remove it to check the capacitance.
BTW, you never did see the backlights even flash on for second?

[Michale32086]

Re: Another Samsung Another Audio-But-No-Display Issue

It is non-polarized cap. You will have to remove it to check the capacitance.

OK, just to clarify.. I need to remove that cap and then check the capacitance on the empty pads??

BTW, you never did see the backlights even flash on for second?

I confirmed.. I darkened the room and plugged it in.. No light whatsoever...

[budm]

Re: Another Samsung Another Audio-But-No-Display Issue

"OK, just to clarify.. I need to remove that cap and then check the capacitance on the empty pads??"
Check the capacitance of the cap you removed.

[Michale32086]

Re: Another Samsung Another Audio-But-No-Display Issue

OK That's where I think I am going to be tripped up.. I don't have a meter that checks capacitance....

[Michale32086]

Re: Another Samsung Another Audio-But-No-Display Issue

On the other hand, I pulled the cap off and there is a slight pimple/bulge on either side of the cap...

[budm]

Re: Another Samsung Another Audio-But-No-Display Issue

It looks bad. Check the capacitance.

[budm]

Re: Another Samsung Another Audio-But-No-Display Issue

OK That's where I think I am going to be tripped up.. I don't have a meter that checks capacitance....

May be its time to get Cap meter that can do capacitance and ESR testing if you are going to do more repair works.

[CapLeaker]

Re: Another Samsung Another Audio-But-No-Display Issue

I'd be replacing it anyway...