Toshiba LCD 26AV502R - no picture but I do have sound

[VictorVictor5]

Greetings all,

First time poster here. Working on a Toshiba LCD 26AV502R for a relative. They told me that there is no picture but they do have sound. So we're halfway there.

I did turn it on, LED comes on, but screen is pure black. No "Toshiba" logo or when I press Menu it does not come up.

Now, back side is off, but I don't see any signs of the obvious (like melted wires and such).

Any suggestions of where to start? I did head over to elektrotanya for a service manual, and it does have a flow diagram to test backlighting.

I'm just looking for some tips. If you all need me to post a pic of the innards, let me know and I'll put it on here.

*Disclaimer - I'm more of a laptop/computer repairer. I've only repaired one TV so far (a Philips CRT). Not the greatest at soldering but it's gotten better.

Thanks all!

VV5

[dskall]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

With flashlight do you see image with menu up? Are backlights on? In darkened room do you have flash when first turned on?

[VictorVictor5]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

dskall,

Thanks for the response.

Let me answer your questions one by one.

With flashlight do you see image with menu up? Yes! Just tried this test. Yay!

Are backlights on? I do not see any backlights on.

In darkened room do you have flash when first turned on? No, I do not notice a flash.

VV5

[dskall]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

Need good clear straight on pictures of back of tv with cover off and each board.

[Andrew F. Ali]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

Could you share the Service Manual you downloaded from Electrotanya, please? Could be Inverter/Driver or Backlights.

[diif]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

You need a multimeter and start by testing for 24v at pins 1-5 on connector P803 (marked in the photo in the service manual) when the TV is turned on.

[VictorVictor5]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

Let me know if these are good enough or if you need close-ups.

First one is of entire back side. Just to orient you, the yellow power board is the top of the TV.

2nd is main board. 3rd is power board. 4th is inverter board.

Let me know if those look good as well.

VV5

[attainteddragon]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

check your voltages on p803. black probe to chassis ground.

list as

pin name, v in stby, v when powered on.

[Andrew F. Ali]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

You need a multimeter and start by testing for 24v at pins 1-5 on connector P803 (marked in the photo in the service manual) when the TV is turned on.

Thank you much, diif

[Andrew F. Ali]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

Also, check the T-CON Bd. Follow the white Flat Flexible Cable from Main Bd passing under the PSU to the top of the Panel Bd. Check the fuse see if it is open and if there is 12Vdc on either side of the fuse.

[VictorVictor5]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

Hey all,

Sorry on the delay - misplaced my multimeter so I had to borrow someone else's

Anyway, per the advice received here so far, and the Toshiba manual, here's what I got:

P803 test:
Pins 1-5, in standby, were about .01-.03VDC, so not much. When the unit was turned on, all pins had a 24.23 VDC reading.

P802 test (per Toshiba flow diagram):
This one was a bit tricky since I had to flip the board over while connected to get my probe on the Inverter pin (pin 16). After I turned in on, I saw it briefly go to ~4.7 VDC and then to zero, so I believe it meets the condition in the flow diagram in the PDF.

If that's the case, the flow diagram says, "If it is available, try one or both inverters. If this does not help, replace the LCD display."

I'm confused about "If it is available, try one or both inverters." Does this basically mean replace the board?

At this point, is it still good to check the TCon board? If so, what am I looking for and what do I test?

Also, any better way to test that pin 16?

Thanks all!
VV5

[Andrew F. Ali]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

check your voltages on p803. black probe to chassis ground.

list as

pin name, v in stby, v when powered on.

Please follow this advice so we could help you better. Are you sure you know how to use your friend's Multimeter.....whos loses the Multitester??

[dskall]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

How about pin 12 and 13

[VictorVictor5]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

As requested:

P803

Pin# Standby Voltage Power On Voltage
1 ~0.01 VDC 24.23 VDC
2 ~0.01 VDC 24.23 VDC
3 ~0.03 VDC 24.23 VDC
4 ~0.02 VDC 24.23 VDC
5 ~0.01 VDC 24.23 VDC

2nd - pin 12 and 13 on P802? Or P803?

[Topcat]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

.....whos loses the Multitester??

Mine has sprouted legs a few times....usually when I need it immediately...

[dskall]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

All pins on p803

[VictorVictor5]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

As requested:

P803

Pin# Standby Voltage Power On Voltage
12 ~0.000 VDC 4.783 VDC
13 ~0.04 VDC 0.185 VDC

Thanks!

[attainteddragon]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

thats better.

you have your inverter on signal and inverter power. so main board is good at this point.

now, on the inverter board, check the dc voltage on each side of the fuse f2 and report back. make sure it is resecured prior to applying power. cover can stay off.

in a dark room, is there a small splash of backlights on start up?

[VictorVictor5]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

now, on the inverter board, check the dc voltage on each side of the fuse f2 and report back. make sure it is resecured prior to applying power. cover can stay off.

Answer: F2 appears to be a surface mount fuse such that it cannot be removed without desoldering. When power applied, I get 0.000VDC across it.

in a dark room, is there a small splash of backlights on start up?

Answer: No, I don't notice a splash on start up.

[VictorVictor5]

Re: Toshiba LCD 26AV502R - no picture but I do have sound

I'm just curious, what does the F2 fuse have to do with the inverter board? Is it the whole fuse for the board?

Just curious on what it controls.