Sony KD-55s8505c restart loop

[ozy]

Hi got a Sony kid-55s8505c that keeps rebooting.
Tried resetting but no joy, could anybody confirm reset is done by pressing vol - on control and power on back of set whilst plugging set in ?
Also tried firmware update via usb but as the tv does not boot its not doing the update.
So I suspect mainboard.
Anybody any ideas ?

[nomoresonys]

Re: Sony KD-55s8505c restart loop

Try holding those two buttons for 30 seconds while plugging and after plugged in or until green led shows, you have a 4 button board correct?

[ozy]

Re: Sony KD-55s8505c restart loop

No it got 7 buttons (pic attached) and as of yet not seen anything from the power led, and it uses the BMFW main board.

[nomoresonys]

Re: Sony KD-55s8505c restart loop

Did you have it hooked up to the internet?

[ozy]

Re: Sony KD-55s8505c restart loop

Yes it was connected via Ethernet originally, but have tried resetting with it disconnected, one time it did boot up and I managed to get in the help menu and it was running firmware pkg5.433.0183eub it then when off and rebooted and back to reboot loop again.

[nomoresonys]

Re: Sony KD-55s8505c restart loop

I've been reading lately where firmware updates have been bricking sonys, I never let my tvs auto update to the latest firmware, I don't update til I know the new update isn't buggy. Matter of fact some updates have been known to take away features that the tv had with the older firmware.

[ozy]

Re: Sony KD-55s8505c restart loop

Yes did wonder if it was a failed update but as there is a newer firmware I assume auto update was off, otherwise it would already have the latest firmware installed

[nomoresonys]

Re: Sony KD-55s8505c restart loop

You can see which number firmware that you have?

[ozy]

Re: Sony KD-55s8505c restart loop

Yes as I said earlier one time it did boot up and I got into help menu to see the firmware version, then it rebooted from that screen and reverted back to original fault.

[nomoresonys]

Re: Sony KD-55s8505c restart loop

Maybe check your boards for bad/cold solder joints, examples there but some are not so obvious: https://www.youtube.com/watch?v=XhlNewlhH3U

[ozy]

Re: Sony KD-55s8505c restart loop

Already done that, few possibles on psu but nothing obvious, resoldered them and all the usual suspects but made no difference, main board looks ok may try a reflow on cpu / ram later, just wanted to see if anybody else has resolved this issue without replacing board.

[nomoresonys]

Re: Sony KD-55s8505c restart loop

Try with power cord unplugged from outlet, unplug cable from powerboard to mainboard, plug power cord back into powerboard, see if backlights come on and stay on, ie if you didn't already.

[ozy]

Re: Sony KD-55s8505c restart loop

did Try that but there was no backlights on, tried with mainboard disconnected and with main and tcon disconnected but not even a flicker from the backlights,
Don’t think it’s a backlight issue though as the boot up animation freezes before the backlight switches off.
Also tried heating and cooling the boards but this doesn’t seem to have any effect either.

[nomoresonys]

Re: Sony KD-55s8505c restart loop

Your tv is about a 2015, I can't imagine it not having pullup resistors, my 2009 does, so when you have the power and mainboards unhooked the backlights should come on and stay on, might not be the only problem but I think it has to do with powerboard or backlights circuit.

[ozy]

Re: Sony KD-55s8505c restart loop

I will have another look later see if I can find bl-on and monitor it or manually trigger the backlight, I did get power led to pulse error 6 when I disconnected the led plug so assuming the current draw from backlight is within tolerance.

[nomoresonys]

Re: Sony KD-55s8505c restart loop

Picture isn't very clear, can you list the pins and their description for the connector on powerboard that runs
to mainboard, might be a lebend/map close by.

[goluins]

Re: Sony KD-55s8505c restart loop

Hi!Please can you help me?My Sony Bravia Kd55Sd8505 with no picture only one center line on white screen?sound good! rm good! new t-con T550QVR but no picture! Please help me!

[Davi.p]

Re: Sony KD-55s8505c restart loop

Don't hijack threads!!

[andrewc]

Re: Sony KD-55s8505c restart loop

Did you manage to fix this?

[andrewc]

Re: Sony KD-55s8505c restart loop

Hi got a Sony kid-55s8505c that keeps rebooting.
Tried resetting but no joy, could anybody confirm reset is done by pressing vol - on control and power on back of set whilst plugging set in ?
Also tried firmware update via usb but as the tv does not boot its not doing the update.
So I suspect mainboard.
Anybody any ideas ?

Did you manage to fix this?