Sony KD-55X8505 not able to start

**nomoresonys** · 06-21-2022, 10:29 AM

Re: Sony KD-55X8505 not able to start

do you get backlights with cable from powerboard to mainboard unhooked?

**PowerAmpFreak** · 06-22-2022, 09:04 AM

Re: Sony KD-55X8505 not able to start

No, when PSU/MB harness disconnected, the PSU is kept in standby.
It's not like the Samsung's when full backlight will be on when cable disconnect.

**dskall** · 06-22-2022, 09:32 AM

Re: Sony KD-55X8505 not able to start

So what is ps-on, bl-on? Did you heat up processor?

**PowerAmpFreak** · 06-22-2022, 09:33 AM

Re: Sony KD-55X8505 not able to start

Originally posted by dskall

So what is ps-on, bl-on? Did you heat up processor?

Heat up processor on MB ?

BL_ON is low constantly. Independent of MB. PS_ON goes high and PSU starts up.

Do you have the service manual or perhaps how the start-up sequence should be ?

Also, no led activity at all. "Smells MB" ??

I tried to force BL_ON high to +3V3 (first disconnect that wire to MB) but there is no led outputs wakes up...

**nomoresonys** · 06-22-2022, 11:01 AM

Re: Sony KD-55X8505 not able to start

Originally posted by PowerAmpFreak

No, when PSU/MB harness disconnected, the PSU is kept in standby.
It's not like the Samsung's when full backlight will be on when cable disconnect.

as long as you're sure, I had an old kdl sony from 2010 that does same as samsung, so it's NOT just the samsungs that self test in that manner, not saying you're wrong, just saying it isn't only samsungs that have that feature.

**PowerAmpFreak** · 06-22-2022, 11:04 AM

Re: Sony KD-55X8505 not able to start

Originally posted by nomoresonys

as long as you're sure, I had an old kdl sony from 2010 that does same as samsung, so it's NOT just the samsungs that self test in that manner.

I believe you, but in this case MB has to pull PS_ON to high at least to power up the power. It seems to be the case also for the BL_ON, but I cannot at all be sure without a service manual or other advice.

**nomoresonys** · 06-22-2022, 11:11 AM

Re: Sony KD-55X8505 not able to start

would probably have to test it as stand alone, using resistors, Diah knows a lot about that process, he helped me test my sony but I forgot the procedure, the memory is the first to go.

**PowerAmpFreak** · 06-25-2022, 07:37 AM

Re: Sony KD-55X8505 not able to start

Anyone know how to test the PSU standalone ?

**Diah** · 06-25-2022, 09:03 AM

Re: Sony KD-55X8505 not able to start

yours TV android. so MB need 12V always on like any android STB box / reciever.......to test the PSB als stand alone. you need external stepdown circuit but in case you don't have one. you can use the MB stepdown circuit. you need to unplug the socket between PSB & MB from MB side.. and just bring one wire from PSB 12V which STB and feed it to the assigned pins at MB socket. look after DC to DC on MB you will find the 3.3V there.. use it to power the PSB as you like.. don't forget BL_ON need DiM pin active too.

**PowerAmpFreak** · 06-26-2022, 07:19 AM

Re: Sony KD-55X8505 not able to start

Originally posted by Diah

yours TV android. so MB need 12V always on like any android STB box / reciever.......to test the PSB als stand alone. you need external stepdown circuit but in case you don't have one. you can use the MB stepdown circuit. you need to unplug the socket between PSB & MB from MB side.. and just bring one wire from PSB 12V which STB and feed it to the assigned pins at MB socket. look after DC to DC on MB you will find the 3.3V there.. use it to power the PSB as you like.. don't forget BL_ON need DiM pin active too.

In this set, it appears MB only needs 3V3 as STBY.
I did disconnect cable between PSU and MB on MB side and pulling PS_ON and BL_ON to 3V3, but I never did with DIMMER so will try again.

New try:
BL_ON
PS_ON
DC_DIM
all connected to 3V3 does not generate any backlight.

Also, 12V T-CON is not on.

**nomoresonys** · 06-26-2022, 08:42 AM

Re: Sony KD-55X8505 not able to start

a backlight tester would be handy in this instance, about 20 bucks on ebay or amazon.

**Diah** · 06-26-2022, 08:46 AM

Re: Sony KD-55X8505 not able to start

always photo on the whole back and the PSU socket pins map will be helpfull if t-CON recieve 12V from PSU direct or via MB. if its from PSU then should have pins like T-CON on

Originally posted by PowerAmpFreak

In this set, it appears MB only needs 3V3 as

first post you wrote 12V only come to MB so the MB have DC/DC stepdown to producse 3.3V which you take it for test

**PowerAmpFreak** · 06-26-2022, 08:55 AM

Re: Sony KD-55X8505 not able to start

Attach pictures.

12V T-Con is coming directly from PSU.
PSU generates +63V to dual boost converters to generate led backlight voltage. But boost converters are off.
No led is flashing.
PSU generates PFC voltage of 393V and 12V output is 12.7V.
STBY supply is 3.5V

Attached Files

**nomoresonys** · 06-26-2022, 09:10 AM

Re: Sony KD-55X8505 not able to start

this tv is 8 years old or so, I would suspect backlights.

**Diah** · 06-26-2022, 09:15 AM

Re: Sony KD-55X8505 not able to start

yours photo

so now its clear you have 3.3V STB.
STB- with Power On you will have REG12V this must be inplace to do further
STB with T_CON ON you will have T-CON VCC12V
STB with BL_ON will post BL

PM Dimmer need R as its low or high

**PowerAmpFreak** · 06-27-2022, 09:40 AM

Re: Sony KD-55X8505 not able to start

Originally posted by Diah

yours photo

so now its clear you have 3.3V STB.
STB- with Power On you will have REG12V this must be inplace to do further
STB with T_CON ON you will have T-CON VCC12V
STB with BL_ON will post BL

PM Dimmer need R as its low or high

Todays test:

3V3 STB connect to PS_ON will make REG12V @ 12.7VDC
3V3 STB connect to TCON_ON will make T-CON @ 12.7VDC
3V3 STB connect to BL_ON does not change anything.
3V3 STB connect also to DC_DIMMER does not change anything.
I would suspect the boost converters to go active? At this point I have not applied anything to PWM DIMMER points.

**Diah** · 06-27-2022, 09:51 AM

Re: Sony KD-55X8505 not able to start

Originally posted by PowerAmpFreak

Todays test:

3V3 STB connect to PS_ON will make REG12V @ 12.7VDC
3V3 STB connect to TCON_ON will make T-CON @ 12.7VDC
3V3 STB connect to BL_ON does not change anything.
3V3 STB connect also to DC_DIMMER does not change anything.
I would suspect the boost converters to go active? At this point I have not applied anything to PWM DIMMER points.

yours PSU look fine.. put all sockets as it should and capture the V on BL sockt between each group of LED+ & LED- at start up ( boot ) check the high and low messurments to compare the groups reading after you finish the test.

**PowerAmpFreak** · 06-27-2022, 10:08 AM

Re: Sony KD-55X8505 not able to start

Originally posted by Diah

yours PSU look fine.. put all sockets as it should and capture the V on BL sockt between each group of LED+ & LED- at start up ( boot ) check the high and low messurments to compare the groups reading after you finish the test.

During boot, the maximum voltage applied from led driver is 63V (two outputs). I think I could power up each led group by a separate powersupply capable of 120V current limited ?

Attached Files

**Diah** · 06-27-2022, 10:15 AM

Re: Sony KD-55X8505 not able to start

Originally posted by PowerAmpFreak

During boot, the maximum voltage applied from led driver is 63V (two outputs). I think I could power up each led group by a separate powersupply capable of 120V current limited ?

you have BL_error on the sockt. if its goes high at boot then you need to be ready for the hard work BL LED

Sony KD-55X8505 not able to start

Sony KD-55X8505 not able to start

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