Sony kdl-40m4000 power related issue

[sputnikoff]

Thhis sony kdl-40m4000 wouldn't power up.No response from power relay and power switch.I measured stby volts at 3.0vdc and it indicated 3.3vdc also ac-off-det was at 1.6vdc.I removed connector going to main board and measured again and stby went to 3.3vdc.I jumped from pins 1 to 3 on PS and power supply came on 383vdc on main cap various voltages on pins of connector goint to main board.I suspect a bad main board.I put connector back on going to main board and jumpered pin 1 to 3.(stby and power) set responds with power relay cycles on/off.So anyone had similar issue.

[dick_barton]

Re: Sony kdl-40m4000 power related issue

What voltage is on Power_On pin when you attempt to come out of standby with mainboard connected?

[Andrew F. Ali]

Re: Sony kdl-40m4000 power related issue

'I put connector back on going to main board and jumpered pin 1 to 3.(stby and power) set responds with power relay cycles on/off.'
Did I interpret that correctly? You could damage your Main Bd. further, though it would appear you have a Main Bd. issue initially.

[sputnikoff]

Re: Sony kdl-40m4000 power related issue

Yes andrew kinda pushed envelope lol.To explain more accurately with jumper on and main board connected the tv's main relay would come on for 1 sceond and then go off repeatedly.I metered the vcc on pin 3 and it was 3 volts not the expected 3.3vdc.I checked resistance to ground of pin 3 to see where load was being drawn from but lost track fast as boards runs are hard to follow.the resistance was quite high so i took chance powering it by force.
Barton pin 1 0vdc pin 2 1.6 ,pin 3 2.96vdc there is some component in main board i believe pulling down stby.

[dick_barton]

Re: Sony kdl-40m4000 power related issue

Barton pin 1 0vdc pin 2 1.6 ,pin 3 2.96vdc there is some component in main board i believe pulling down stby.

Pin 1 - Power On
Pin 2 - AC Det On Off
Pin 3 - 3.3V

If you jumped Pin 1 to 3 and all the supplies came up to their correct voltages then it looks like you have a mainboard fault.

[budm]

Re: Sony kdl-40m4000 power related issue

I would put DC A meter in series with the 3.3V STBY wire going to the main board to see how much current the main board is trying to pull.

[budm]

Re: Sony kdl-40m4000 power related issue

Service manuals:

[sputnikoff]

Re: Sony kdl-40m4000 power related issue

Thanks guys always a wealth of information here.

[budm]

Re: Sony kdl-40m4000 power related issue

Extracted circuits from service manuals.

[sputnikoff]

Re: Sony kdl-40m4000 power related issue

wrong model

[budm]

Re: Sony kdl-40m4000 power related issue

wrong model

??????

[sputnikoff]

Re: Sony kdl-40m4000 power related issue

The power is being loaded down from power supply from 3.3 down to 3vdc.I metered resistance with connections removed from video board and tested from ground to pin 3 stby pin and getting 1.8 ohms roughly . The diagram is difficult to follow as components aren’t listed like d3020 and d 3021 as listed in schematic.i see on diagram I suppose it’s called silk screen where components are laid out that fb1011 is listed there in diagrams but not on components list.seems stby circuit is not too complicated but my inexperience being out of repair tv so long is showing.problem is can’t seem locate components on board as there is limited print on board.