Vestel 17MB61-2 No picture

[SA6BUQ]

Hi all, I have searched and read as much as I can but did not find a suitable similar case, so that is the reason for posting.

Vestel 17MB61-2 branded as Andersson A424FDC (42 inch LCD) in Sweden.
Power Supply 17PW26-4 Seems to measure OK PL816:
Pin 6 : ST_BY = 0V when powered on
Pin 12: +12V OK
Pin 14: +5V STBY OK
Pin 15, 16: +3.3V OK
Pin 18, 19, 20 : +3.3V when powered up
Pin 11: +12V =OK
Pin 13: 33V = components not fitted on PSU
Pin 17, 19, 21 : +5V OK

Symptoms:
Powers up using keypad (top button). No picture no sound.

PSU board PL802:
+24.33V to T-CON OK
+3.33 BL ON to T-CON OK

After pressing the On button, the front LED blinks about 12 times and then the backlight turns on. No picture or text on the screen but dim light blue glow.

Measured Voltages on U25 and U26 on the Main board as well:
U25 : In 5.1V, Out 2.82V, Adj 1.57V (Strange output voltage?)
U26 : In 5.1V, Out 3.4V, Adj 2.15V Looks OK

It almost seems as if most is working and that there may be a bootup or firmware problem?

Any thoughts, advice will be much appreciated. Thanks in advance.

de SA6BUQ

[dick_barton]

Re: Vestel 17MB61-2 No picture

+24.33V to T-CON OK
Are you sure it's 24V to the tcon. Have you checked the fuse on the Tcon board. Have you connected to the scart connector to check for sound.

[SA6BUQ]

Re: Vestel 17MB61-2 No picture

Hej Dick, thanks for the reply.

Well, I am not a specialist and if I understand it correctly the T-CON board is the one on the left (when looking from behind the set) under the blac metal cover. The cable connected from there to the PSU to a header marked PL802 on the PSU board. The right hand 4 pins are connected to red wires and measure +24.33V. Where is the fuse located on the T-CON board?

I have not connected a SCART source and sorry, but I omitted to say that I can not turn on the set using the remote, so I cannot select a different input source using the remote. When pressing the buttons on the side, they beep with every press, but nothing happens on the screen e.g. volume control slider bar does not even appear.

Willing to do any more measurements/checks that you may recommend.

Thanks again. 73 de SA6BUQ

[vinceroger69]

Re: Vestel 17MB61-2 No picture

can you upload a picture showing the whole of the back of the tv so we can see how the boards are connected as its sounds like you maybe testing the invertor board hence the 24v reading.

[dick_barton]

Re: Vestel 17MB61-2 No picture

can you upload a picture showing the whole of the back of the tv so we can see how the boards are connected as its sounds like you maybe testing the invertor board hence the 24v reading.

+1
Inverter boards normally at 24V. Tcon at 12V or less but often 12V.

[ReeceyBurger123]

Re: Vestel 17MB61-2 No picture

Agree with Vince if I recall this cmo panel uses an inverter with them crappy AO mosfets on that seem to short out and blow the fuse.

[SA6BUQ]

Re: Vestel 17MB61-2 No picture

Here comes the rear view pics... the +24.33V I measure is on the right hand 4 wires of PSU (maybe the same thing as the inverter board?) board PL802 which then goes to the board with the black cover on the left.

Regards SA6BUQ Christo

[SA6BUQ]

Re: Vestel 17MB61-2 No picture

...I removed the cover and measure the 10A fuse...(marked in the red square) there is a label just below it showing 24V. Is this the inverter board or ?

[dick_barton]

Re: Vestel 17MB61-2 No picture

...I removed the cover and measure the 10A fuse...(marked in the red square) there is a label just below it showing 24V. Is this the inverter board or ?

Yes, that's your inverter board.
There are 2 fuses. F1 & F2. set off and use your meter set to ohms and measure across each in turn. They should both be short circuit (0 ohms).

[vinceroger69]

Re: Vestel 17MB61-2 No picture

looking at the pictures this set looks like the tcon is built onto the lcd panel pcb (bonded on the lcd?) post 7 picture 2 black lead from mainboard running to top center of tv im not sure how easy it is to get a picture of the area as on that board you will find another fuse to check.

[SA6BUQ]

Re: Vestel 17MB61-2 No picture

Hej and thanks again, Dick I measured F1 and F2 and they both measure 0 ohms. When the set is on (with backlighting showing) i measure +24.33V on both. So they seem to be OK.

Roger, there are 4 mounting points on the chassis above the PSU board that are not used.. clearly this chassis was used for older versions where the T-CON board was mounted there. So it must be integrated with the panel somehow as you say... maybe high speed serial..because there are not enough wires to address the LCD transistors. Anyhow.. I attach a photo of the connection on the top.

To get into that I will have to strip quite a bit... any other thoughts to why there is no text on the screen will be appreciated.

Thanks again. 73 de SA6BUQ, Christo

[ReeceyBurger123]

Re: Vestel 17MB61-2 No picture

So the backlight is working ?

[ReeceyBurger123]

Re: Vestel 17MB61-2 No picture

looking at the pictures this set looks like the tcon is built onto the lcd panel pcb (bonded on the lcd?) post 7 picture 2 black lead from mainboard running to top center of tv im not sure how easy it is to get a picture of the area as on that board you will find another fuse to check.

Mb does 75% of the timing processing for the Lcd hence more ic's on it, but board on Lcd just unpacks it all to the tab drivers.

[vinceroger69]

Re: Vestel 17MB61-2 No picture

Thanks reece another thing ive learnt about these boards.

[SA6BUQ]

Re: Vestel 17MB61-2 No picture

Yes, ReeceyBurger it lights up as mentioned in the 1st post...that is the strange thing.. all voltages seems to be fine. I get no text/image on the screen though.

Not sure where to look next... checked the LCD.. no cracks, drops, dents.. and the backlight is evenly spread across the screen.

I've worked on a few from Plasma's to LCD, and this one has NO strange noise, caps or symptoms... apart from the LED in front not blinking when I press any button on the remote....

Any thoughts will be helpful.. I am willing to share/post any measurements, pictures that may help...

73 de SA6BUQ, Christo
(in Sweden where things are tossed instead of repaired..Hi)

[SA6BUQ]

Re: Vestel 17MB61-2 No picture

Hej again,

So my thread on the Vestel here went a bit quiet. I hope I did not annoy anyone.

My mistake in the original post:

PSU board PL802:
+24.33V to T-CON OK
+3.33 BL ON to T-CON OK

The cable from the PSU runs to the backlight inverter board (not T-CON as written). There is no seperate T-CON (see post from vinceroger).

Any more tips or thoughts on what could be wrong with this Vestel?

Regards

SA6BUQ