samsung LA32C530 LCD TV not powering up (relay clicking)

[jork]

Hello,

long story short, I bricked my TV :-(
Mine is a 2 year old samsung LCD TV, it is not powering on now. No response for the remote or the touch pad. I can hear a periodic relay clicking sound though. Initially I thought it could be the badcap issue. So checked the power supply board. there is no bad caps. I checked the voltage levels on the standby and the IR/touch pad key press responses on the PIN. the standby shows steady 3.3V. when I disconnect the mainboard with PSU, the backlight is on, otherwise no.
One thing I noticed is the 12v lines are fluctuating. It goes up till 12V and then when the relay clicks, it goes to really low values (~1v). Is this expected? what could be the problem here? Powersupply ? mainboard? Please help.

[tom66]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

How did you "brick" your TV? This may be very important in unbricking it!

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

thanks tom66 for the quick reply.

ok. it all started with a whole different problem. One fine day my TV started showing two images on the screen. One regular image and about 1inch below it, another less bright image- looking like a shadow of the first one. So, I did a routine service centre call. The guy came home and without even trying a bit on diagnosing the problem, blindly said you have to replace the panel. And the cost was absolutely not acceptable.

So, I thought let me give it a try. I did some research on internet, mostly this forum. And I saw many of the folks suggesting this is a classic case of T-CON problem. while debugging on that side, I tried remove one of the two T-CON to panel conenctions and that side was perfectly fine (no shadow issue). Now I removed it and tested the other side. There was the shadow problem, on that side. So, now it could be a panel problem on that side or the T-CON problem. So, to narrow down further I tried connecting the left side T-CON connector to the right side of panel. (if this worked, I will confirm the right T-CON problem and replace it happily). But then when I switched on the tv with this, it didn't turn on and then whatever I do, the TV is not turning on. I really don't think the T-CON test burned the motherboard. So i'm trying to debug from that time for ever :-)

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

The TV is an indian variant of LE32C530xxx.
Mainboard - bn94-08787a
PSU - BN44-00339C (this is same as BN44-00339A and compatible with C)
T-CON - XX94-J3256H

please let me know if you need me to post any more details or the photos of the board.

thanks,
joe

[budm]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

That is not good idea trying to drive the opposite side of the connector. Disconnect the LVDS cable from the main board that feed the T-CON board and see if you can turn the TV ON/OFF.

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

Hi Budm, I did disconnect the LVDS cable from the mainboard. No difference (no backlight, no tv on, the frontpanel led is not even blinking as a sign of turning on). Now I disconnect the mainboard, the backlight is back.

As I mentioned in the first post, I'm seeing a fluctuation on the 13v line. the voltage is varying from 1-13v and then going down slowly. The variation is somehow related to the relay click. Is this the way 13v line behave all the time or should it be constant?

[tom66]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

Check the PSON line, is this unstable, may be in time with relay clicking?

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

The PS_ON is varying but with very low values (from .02 to .9) again in sync with relay click. Just after the relay click the volages comes up to the rating and then start decaying. this is happening with 13v as well as 5V. But the 3V is stable. Also, one more thing I noticed is, after disconnecting the PSU from main board, all the voltages are stable and the backlight is working.

[tom66]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

Does the main 5V rail vary too?

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

No. the main 5v line which I think is marked as A5v1 doesn't vary. Also, the voltages on the IR panel pins also doesn't vary.
below are the voltage on PSU cable connector

A5v1: 5v always
B5v1, B5v2, B5v3: 0.1 - 5V varies
B13v1,B13v2,B13v3, B13vs1,B13vs2: 0.5 - 12.5 varies
LAMP_DETECT, SW_INVERTOR: 0 always
PWM_DIMMING : 0.1 - 1.5 varries
H_SYNC: 0.1 - 5 varies.
PS_ON: 0.1 - 0.9 varies

these are the voltages on IR panel PINS

IR_A3.3v, IR_NC1 : 0
LED_STD: 1.5
KEY2, KEY1,MSDA, MSCL, A5v2, IR : 3.3

Also, the key2,key1 and Ir PIN voltage changes (goes down) when I press the keys or use remote, indicating a input response.

[tom66]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

Try unplugging the speakers. Is it any different?

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

speakers were already unplugged. just now I tried putting back in. No difference at all. I guess the speaker line will will get activated only after the board boots up right? here, the board is not yet powered up. I tried sensing the ps_on during key press for poweron too. No difference.

[tom66]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

This TV is probably active low power on, so can you get a 100 ohm to 470 ohm resistor, put it between PSON and GND, and see if TV stays on and 13V is stable?

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

I will try that out and post the result. btw, can you tell me what is active low power on state? And I was wondering why would the voltage fluctuate, though powersupply seems fine as voltages are stable if i disconnect psu and MB. Or is that, the PSU is not able to sustain when a load is connected?

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

hey tom,

I tried pulling in the PS_ON with a 200ohm. but everything is same.

[tom66]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

As in, the 13V fluctuates still?
Active LOW means that when that pin is low the power supply is on. Active HIGH means when a pin is high the power supply is on.

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

yeah, thats what I observed. After connecting the resister, the behavior was exactly the same. Same fluctuations, no tv on or backlight on.

[budm]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

I believe this power supply is Active high, the pull up resistor is on the power supply board, the main board transistor is normally on to keep the PS_ON line LOW to keep the TV off, the transistor is turn off which causes the PS_ON to go high. If you disconnect the power cable from the main board to the main board, the Power supply will run on, same for the backlights (BL_ON line also has the built-in pull up resistor), you will see >3v at the PS_ON pin on the power supply board when the wires are not connected to the Main board. What you can do is to cut the PS_ON wire and the BL_ON wires (leav them long enough to be able to splice them back together), have the connector hook back up between the main and the power supply board. When you plug the TV to the outlet , the backlights should come on right away, then hit the power switch to see the power LED will be active. At this point it looks like you have problem with the main board for sure.

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

I will definitely try that out today evening. Even I feel it could be a problem with the mainboard. but wanted to be sure as the powersupply voltage variation kept me thinking.
So, how do we debug the mainboard problem in more details if we want to. Now we know that the remote/touchpad input is being given to the MB. but mainboard is failing to take any action with that. If we know the exact logic flow, we could've traced that I guess.

also, is there anyway to get a service manual for this board. I searched a lot in internet and the samsungspares site as well. couldn't find a service manual anywhere. with that we could ve got a better idea of the testpoints.

[jork]

Re: samsung LA32C530 LCD TV not powering up (relay clicking)

Hi Budm, I have tried exactly what you suggested. As you said, I'm seeing the PS_ON on PSU side having >3v. But the backlight is not turning on. It just blinks once and then stay off. When I switch off the outlet also, the backlight blinks once again.

One interesting thing I'm noticing with this is, all the 13v and 5v lines are steady now and the relay is not clicking anymore. but nothing happens when I try to switch on the TV. Also, the PS_ON on the main board side is showing some varying signals (fluctuations)