Samsung 32" LNT3242HX/XAA will not boot on, steady led light

[lucidbarrier]

Hi all,

My girlfriend's sister gave me her TV to look at because it would not turn on. It has a push button with a red led standby light in the bottom center of the TV that is continuously lit when the power cord is plugged in. I have a similar TV in my bedroom, I thought it was the same and was hoping it was a simple capacitor swap job like mine was but it turns out the model numbers are different.

The TV will not boot up, usually when you press the center button or remote, the standby light will begin to blink after a few seconds and the TV boots on with a chime. When you press the button or use the remote, it stays in standby mode. GF's sister turned off the computer connected to it (HDMI) and the TV went into standby mode, and the red led light was blinking. The next morning the standby light was steady but the TV wouldn't turn on.

I removed the Power board, BN44-00192A model MK32P3 and looked it over and only found one questionable cap, a 10V 1000uF (Samwha), none of the capacitors looked bulged though, it just looked like plastic casing was peeling away. After I removed it, I hooked it up to my ESR Micro v4.0s and got a 0.00 Ohm and 965uF reading.

I decided to do the shotgun capacitor swap with caps from a local distributor. It still will not boot up.

Anyone familiar with this model? I did a search on this board and an ebay seller says to replace this big ol' aluminum 35mm 450WV 150uF cap if the indicator light is red but it wont boot up.

No luck, TV still will not boot up.

[lucidbarrier]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

I just noticed that the parts guy gave me a Nichicon 85C general purpose capacitor for CM852 10V 2200uF, all the other ones are 105C.

[budm]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

First, you need to remove all those glues, and inspect real close to see if any of the component legs/wires are eaten away, and look for black carbon traces. Scrape them off as much as you can and use alcohol to soften the glue.
https://www.badcaps.net/forum/showthread.php?t=34692
Then you need to look at the voltages on the connectors, there should be labels close to the connectors to tell you what it should have.

[audiofreak19]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

I have the same tv as a parts tv. I also fixed a bunch of these. I have never had a problem with 85c caps when I was first starting out. You might have a main board issue if it won't respond to the power button

[lucidbarrier]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

Ok I started cleaning up this glue, the CM810 had black gunk traced between the leads and there was some really dark brown crusty glue on some other components. I cleaned it up with some alcohol and tried it back in the TV just for fun, still wont come on. I will break out the multimeter tomorrow and figure out how to test the different voltages. I was watching a video earlier and it said to short out PSON to supply voltage to the different connectors.

I am starting to think that it may have a bad main board too, the board has a thin film of oil on it, all over the bottom half of the board.

[audiofreak19]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

Post a pict of it too

[lucidbarrier]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

I went to radioshack to buy a mini test lead kit to make this easier, my probes were too fat to fit inside the body of the connector to get readings.

Ok with the board mounted in the chassis I unplugged both connectors at the main board from the power supply. Powered on, Negative probe connected to a heatsink:

PSON measured 0 Volts and 5VStdby had 5V, as expected

I jumpered a 150ohm resister from PSON to 5Vstandby (pin 1 and pin 3) and:

PSON measured 4.99V and 5Vstandby had 5V as expected, and I heard a light click (when probed with positive lead)

CNM801 connector:

pins 7, 8 expected 12Volts, measured 0 Volts , registered a light click when probed

pins 13, 14, 15, 16 expected 12 volts, measured 0 volts, registered a light click probed

pins 19, 21, 22 expected 13 volts, measured 0 volts, registered a light click when probed

CNM802 connector:

pins 1, 2, 3, 4, 5 expected 24 volts, measured 0 volts, no clicking sound


Am I doing something wrong? I am not getting readings on any of the voltages except for
PSON and 5V Standby, and I double checked those to make sure the negative probe was still connected. The meter was definitely doing a reading because it shows auto and it has an indicator that its actively metering.

[mmartell]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

Try unplugging main board from PS (and anything else except a/c in) and jump pson. What are the voltages now ?

[vinceroger69]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

try holding the negative lead on the metal chassis of the tv and retake the readings.

[lucidbarrier]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

Unplugged CNM802 connecter with the 24V rail, only thing connected is A/C power, no change.

Switched the negative probe to chassis ground, no change, only PSON and 5V standby have voltage.

[mmartell]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

Unplugged CNM802 connecter with the 24V rail, only thing connected is A/C power, no change.

Did you leave the other two connectors plugged in or remove them as well ?

[lucidbarrier]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

They are plugged into the power board but unplugged from the main board. I jumped PSON to the 5Vstandby using a resistor on the main board side of the connector. Not sure how I would jump it otherwise, other than flipping the board over and soldering it.

[vinceroger69]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

is 150ohm resistor high enough? i use a 1k just a thought someone more experienced will advise i hope.

[budm]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

OK, when you force on the power supply, the first thing that needs to happen is that the dc voltage on the main filter should jump up from 165Vdc (PFC Circuit turns on) to around 370~400Vdc (you MUST measure right at the two legs of the cap). If the the boosted voltage is not working, the 12v/24v power supply will not work because it needs that high voltage to run.
CM808 is the commonly failed cap if you do have the 360~400VDC. RM801 is OK, right?

[lucidbarrier]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

Its definitely the power supply, I was reading another thread and went to this site called shopjimmy, it had substitute part numbers, so long story short, I put the one in my TV (BN-00191B) in this unit and it powered right on.

The main filtering cap is the 35mm CP803 right?

With A/C connected, I get a steady 167.3 Volts across CP803 and also across RM801

When I had the board out, the ESR on CP803 was .52 ESR and 130uF capacitance.

[budm]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

Yes, CP803. When ps_on is applied, the voltage should jump up from 167Vdc to 360~400VDC if the PFC booster circuit is working. You need to have boosted voltage working first before going further.

"With A/C connected, I get a steady 167.3 Volts across CP803 and also across RM801"
What do you mean by across RM801? it should show about 0V because it is less than 1 Ohms resistor, it cannot have 167VDC across it (measured between the two legs). If you do, that means the resistor is open.

[lucidbarrier]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

Voltage across CP803 was steady 167Vdc, it did not jump up at all.

RM801 showed a voltage of 167 Volts across the legs in circuit. I desoldered one leg of the resistor and it shows 0.F

My meter only goes up to 500V, is that going to be a problem?

Edit: after removing the resistor there is a noticeable burnt mark near the underside of the resistor. This is a .22Ohm resistor?

[budm]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

That is fusible resistor, either 0.22 or 0.33 Ohms, it is used to protect further damage if the MOSFETs for driving the 12V/24V transformer shorted out or draw too much current due to bad glue become conductive. When you said it shows 167VDC across the two legs, it tells me right away that you have open resistor.
So right now you have two problems, the PFC Voltage booster is not working, the MOSFETs for the 12V/24V SMPS may be bad. Not a good sign.

[lucidbarrier]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

That's actually not bad news, I am going to order a replacement board and go from there. I wanted to see if I could get this board up and running but if its unsafe/unfeasible to repair then chalk it up to fate. I learned a ton messing with this thing and I appreciate the help.

I see another thread where a similar board BN44-00155A has the same RM801 popping and CM810 with carbon tracks between the legs.

https://www.badcaps.net/forum/showthread.php?t=17044

[raiderfanpat]

Re: Samsung 32" LNT3242HX/XAA will not boot on, steady led light

That's actually not bad news, I am going to order a replacement board and go from there. I wanted to see if I could get this board up and running but if its unsafe/unfeasible to repair then chalk it up to fate. I learned a ton messing with this thing and I appreciate the help.

I see another thread where a similar board BN44-00155A has the same RM801 popping and CM810 with carbon tracks between the legs.

https://www.badcaps.net/forum/showthread.php?t=17044

Thanks a bunch!,, i had a bad small blue cap next to that big CAP which took out the fuse resistor. replaced both blue cap and resistor and power supply fired up! THANKS AGAIN!!