Sony KDL-46R450A No Power, No red LED status

[joeward]

Hello all,

I've been trying to solve this issue and maybe someone can make me check in the right direction.
Sony KDL-46R450A no status red LED, no Green LED, no power. TV wouldn't turn on 6 hours after beeing turned off last week
PSU 1-888-122-12 (GL5 APS-350)
Some kind of relay click is present on PSU. repeats every 4-5 seconds.Power button pressed makes no difference.

Cable to mainboard voltages measured at different pins
Ground taken from Ground Screw on secondary in all tests (except for Primary cap)
(PSU AS IS still hooked up from inside TV.)
1 GND
2 VCC_3.3_STBY = jumps from 0.6V to 1.14V after each "relay" click
3 GND
4 POWER_ON/OFF = 0V
5 VCC_12V = 0V
6 ACC_OFF_DET = 0V
7 VCC_12V = 0V
8 BLKT_EN = 0V
9 AUDIO_12V = 0V
10 BL_CNTL = 0V
11 AUDIO_12V = 0V
12 BKL_ERR = 0V
13 VCC_12V = 0V
14 GND
15 VCC_12V = 0V
16 GND
Main CAP from Primary (450V 82uF) measured straight at pins voltage jumps from 240V to 260V at each relay click

If I disconnect cable from PSU to Mainboard (Differences from previous results)
no relay clicks
2 VCC_3.3_STBY = 3.3V
6 ACC_OFF_DET= 3.3V
Main CAP from Primary = 164V

Took PSU out of TV Checked Main Fuse (not open) and different components.
no relay clicks
Put a 1k Ohm between VCC_3.3_STBY and POWER_ON/OFF:
2 = 3.3V
4 = 3.3V
5 = 12V
6 = 3.3V
7, 9, 11, 13, 15 = 12V
8, 10, 12 = 0.02V
Main CAP from Primary = 399V

I ve checked many fuse resistors none are open, no indication of burned components
Checked mosfets none seem shorted

Any help on anything I should look for next ? Could it be a mainboard issue ? I just find it weird with the no power at all.
Thank you so much

[dskall]

Re: Sony KDL-46R450A No Power, No red LED status

I would say you have a mainboard problem.

[nomoresonys]

Re: Sony KDL-46R450A No Power, No red LED status

go ahead and add a 1k resistor from bl_cntl to standby along with the other jumper and see if the backlights come on, leaving the cable from powerboard to mainboard unhooked of course.

[joeward]

Re: Sony KDL-46R450A No Power, No red LED status

Thank you for the reply

I just tried adding 1k ohm from standby to bl_cntl keeping the other one there as well and no backlight came on.
Cable from powerboard to mainboard disconnected, just LED cable connected to powerboard (CN6801)

[nomoresonys]

Re: Sony KDL-46R450A No Power, No red LED status

ok, I don't know if you also need blkt_en jumped to standby also or not, I can not say for sure. I think it means backlight enable but not positive.

[joeward]

Re: Sony KDL-46R450A No Power, No red LED status

I just tried adding another 1k ohm to blkt_en and this time yes, I do have backlights on. Does this confirm a faulty mainboard ?
thank you for all the help !

[nomoresonys]

Re: Sony KDL-46R450A No Power, No red LED status

pretty sure it means your backlights and powerboard are ok, so could be mainboard or tcon or panel I suppose.

[nomoresonys]

Re: Sony KDL-46R450A No Power, No red LED status

maybe try some isolation, maybe start with unhook ribbon cables from tcon to panel driver board, then see if the clicking stops, if not then unhook lvds cable from tcon or mainboard, see if clicking stops, there was no clicking with cable from powerboard to mainboard unhooked right? I always make all connect and un-connects with tv unplugged from power, to try to avoid any errant surges and such.

[joeward]

Re: Sony KDL-46R450A No Power, No red LED status

in any combination I do hear the clicks.
Last combination was everything unhooked from mainboard (Cable ribbons and cables) leaving only cable from powerboard to mainboard and sadly I still hear the clicks.

edit: sorry forgot to say: right, if cable from power board to mainboard is disconnected i don't hear the clicks

[nomoresonys]

Re: Sony KDL-46R450A No Power, No red LED status

ok, I'm thinking mainboard issue too.

[nomoresonys]

Re: Sony KDL-46R450A No Power, No red LED status

Dskall nailed it in only 1 post,

[joeward]

Re: Sony KDL-46R450A No Power, No red LED status

He absolutely did nail it in one post !

Thank you to the both of you for the help and the double checking.

[joeward]

Re: Sony KDL-46R450A No Power, No red LED status

Just as a follow up, I did replace the mainboard and TV is back and running.

thank you again for the help