Toshiba 37X3030D backlight issue

[diif]

Hello, I have a Toshiba 37X3030D here.
Initially when I powered it up the relay would click, the green light would come on but there would be no backlight and the TV would click again and turn to standby a few seconds later. I measured the voltages as per the markings next to P8078 and P8068, they were all present apart from the 24v_INV at about 200mv. There was also a strange "TINK TINK TINK" noise coming from C804 with the voltage fluctuating wildly on pin 1 of Q801.
Normally i'd try and diagnose and repair but a second hand one was super cheap so I didn't bother.

The new power supply turned up and i've fitted it. Now when i switch it i get about 18v at 24V_INV before it drops away to about 3v.
No backlight but the TV stays with the green LED on.

Have i got a dodgy power supply, or should i be investigating the inverters and CCFLs ? Thank you.

[comptek]

Re: Toshiba 37X3030D backlight issue

unplug inverter to see if voltages stay up

[ReeceyBurger123]

Re: Toshiba 37X3030D backlight issue

Thought you fixed it ? Also got an image of the inverter bud ? Also do what CT says and unplug the Inv and see if the 24v stays up.

[diif]

Re: Toshiba 37X3030D backlight issue

I thought it was going to be a simple power supply swap Reece.

I've unplugged both of the inverters and no, I get about 16v before it drops away.

[budm]

Re: Toshiba 37X3030D backlight issue

We need to see the pictures of the whole backside of the TV so we can see how all the boards are connected together.
Did you try the OLD power supply board without having the inverter board connected to it to see if you get 24Vdc?

[diif]

Re: Toshiba 37X3030D backlight issue

Here we go.

Yes budm, the same unstable 300mv with the original power supply.

[budm]

Re: Toshiba 37X3030D backlight issue

Are you getting about 400vdc between the two legs of the main filter cap? Look like you can test that on the two empty pads next to the main filter cap.

[diif]

Re: Toshiba 37X3030D backlight issue

No, only 334v

[budm]

Re: Toshiba 37X3030D backlight issue

No, only 334v

OK, I need to see good clear straight shot pictures of this power supply board.

[diif]

Re: Toshiba 37X3030D backlight issue

I hope these are ok ?

[budm]

Re: Toshiba 37X3030D backlight issue

I hope these are ok ?

I am sorry, I mean the bottom side of the board, those top side pictures are good so I can use them also to make virtual PCB.

[diif]

Re: Toshiba 37X3030D backlight issue

Thanks.

[budm]

Re: Toshiba 37X3030D backlight issue

Thanks, I will have to trace out the connection to see what is going on.

[budm]

Re: Toshiba 37X3030D backlight issue

OK, it does not use PFC Boosted Voltage circuit, just simple inductor for PFC, so the 334VDC on the main filter cap is normal.
Now we need to find out why you are not getting full 24VDC for the inverter board.

[budm]

Re: Toshiba 37X3030D backlight issue

BTW, you have indicated that the new board puts out about 16V and then drops out, did you hear the relay on the bottom right of the board drops out?
https://www.badcaps.net/forum/attach...0&d=1463157984

[diif]

Re: Toshiba 37X3030D backlight issue

If the power supply is at fault I can send it back and get a refund as it was sold as tested and working.

[budm]

Re: Toshiba 37X3030D backlight issue

Please see post 15.

[diif]

Re: Toshiba 37X3030D backlight issue

No, the relay clicks once when I power on, but it does not click off.

[budm]

Re: Toshiba 37X3030D backlight issue

OK, that is good.
Please check the capacitance of that orange cap C??? next to the relay.

[diif]

Re: Toshiba 37X3030D backlight issue

C803, on the original board it's 108nf on the replacement 182nf. It's marked 104J 630.