JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

[budm]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

I found some SCH for the the 17IPS20 series (4 versions that I found) but none match his board layout.
The SCH I look at has to feedback error signal to tell the main board if BL-ON is present at the power supply board or not, or any error signal to tell the main board if the LED drivers are not functioning.
But you probably right that the Boosting circuit is not working at this point, he can get the spec sheet of the IC to do some Voltage testing or get the new IC since you already experience with this failure in the VESTEL.
BTW, I still do not like those 3 LEDs which are not on, it means they are not in the same condition as the rest of the other LEDs.

[PL519]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Hi,
i´m working on exactly the same chassis, only difference it´s a telefunken brand type D42F182N2, age: 2 years and two month, just out of warranty. Customer told me that screen went totally black from one second to the other. First assumption was backlight LED´s. With the information from ReeceyBurger123 (thanx to him) about the voltages i built this nasty chain of high current led modules from Citizen. They are normally driven by 350mA constant current which leads to a drop-out voltage of abt. 33V. 5 of them in series could well fit the output voltage of the LED driver. I applied the chain to the driver, switches the set on and voila: all modules lit, changing their brightness in three steps during boot up process. ReeceyBurger123´s info abt. voltages verified. So this could be a good method for quickly testing the driver or the led´s in the panel. Maybe helpful for somebody?!
Greeting,
Wolf

[ReeceyBurger123]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Its ghetto but it works at least, maybe a little more isolation of the terminals of the wires will make it more safe but good overall idea to test it. Thanks for the feedback too

[PL519]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

yeah, you´re damn right. It was just a "blip" in my old brain and i wanted a quick and dirty realisation.
BTW, can you tell me how to get access to the led-stripes inside the panel? Doesn´t seem to be an easy process without damaging it.
TIA,
Wolf

[ReeceyBurger123]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Its not easy I tell you, for your panel Ves420 you need to do this:

1. Remove stand support brace and unplug Tcon ribbon cables that go to screen driver board.

2.Unscrew front Led and Ir sensor board and optic from the front frame.

3.Unscrew all screws around the outside out the metal frame going to front plastic bezel.

4.Flip Tv over and pry off front bezel its clipped down so just undo the clips by folding it outwards.

5.After removed unlatch tab bond driver pcb from metal chassis fold both over onto lcd screen and tape down to stop it from flexing.

6.Carefully remove Lcd screen and place some where safe, be very careful here hold it by the sides try not to flex it !

7.After that there is another black plastic bezel that holds diffusers down, its secured with clips unlatch them and remove platic bezel.

8.Grab all the diffusre sheets together and place them aside in the orginal order.

9.Remove the white reflector sheet off the back on the panel, there are 4 plastic optic clips that hold it down as well as some double sided tape. The clips are secured throuh the underside of the metal chassis.

You then have access to the Leds.

Or watch my video which covers the Ves315 Led screen which is similar to take apart:
https://m.youtube.com/watch?v=0uBhca7zyXI

If you crack the screen the game is over to be very careful. Good luck and keep us updated

[PL519]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Hi ReeceyBurger123,
thanx for Your advice. Did it nearly the same way as You described, but lifted the lcd with the plastic bezel, seemed to be a little more safer for the display. Anyway, after that it was easy to locate the defective lcd, took it out and managed to exchange it with a similar one from a telly with a broken screen. Everything fine now, all led´s lit up. Just waiting for the glue holding this little optical lens now to dry up, then i´ll reassemble the unit again.
Thank you Vestel, you gave my afternoon a real sense https://www.badcaps.net/forum/images.../icon_razz.gif.
ReeceyBurger123 many thanx for Your assistance and good luck to tn245, who started this topic!
Wolf

[ReeceyBurger123]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

No worries glad to help, also reply is late because it didnt post for some reason lol

[comptek]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

i aways use cotton or latex gloves saves finger prints on the inside of the screen

[ReeceyBurger123]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

i aways use cotton or latex gloves saves finger prints on the inside of the screen

I dont have to I sort of slot he screen sides between my hands so that I dont have to put my hands on both sides.

[tn245]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Just to update. It's had new driver IC and FETs Q502 & Q505 plus R509 which was out of spec. Boosted diode (D504) tests ok and have also tried a replacement. Sent PSU to Michael Dranfield who said it was was working for him after R509 replaced but in my set it is not. With LED string connected or not, voltage never gets above 123V. Maybe a problem with dimming signal from main board? I may try to cobble together an oscilloscope to check out the PWMs but I'm having to put the TVs aside till next week so will get back to it then.

Pictures of the back of the board and LED driver section attached.

[ReeceyBurger123]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Hmm why dont you test them dim Leds with your DMM ?

[tn245]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Hi Reecey. I was for the time being ignoring the LEDs and concentrating on the PSU as shouldn't it still be hitting something above 123V with the string disconnected - even if briefly?

[ReeceyBurger123]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

It should be hitting that then detects that the Leds are not getting power then collapse. Does it still not do that ? Also what did Michael actually replace ?

[tn245]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

It doesn't as far as I can tell. Unless my DMM's (UNI-T UT61E) peak function is not fast enough to catch it? Replaced parts are U500, Q502, Q505 and R509.

[ReeceyBurger123]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Any update on the set ? I recent had a 17ips20 with no 24v for the Leds found the transistor for the 24v/Led driver was not being turned on. Two shorted smd diodes on the bottom of the psu. Will link video which helped me diagnose it shortly.

[tn245]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Yes. I have borrowed a known good PSU and main board for testing. It seems the PSU was ok but there is some issue with the main. There does seem to be a problem with the LEDs too as the borrowed boards are not always able to light the backlights although with the new main I am getting the higher voltage at start-up on both PSUs.

I will try reflashing the firmware on the main and also will test and replace LEDs as needed. I am short of time to work on this set though.

[ReeceyBurger123]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Hmm maybe it is a fault with the Leds then. As I said you need to test them 3 not glowing with you DMM not the 12v Psu.

[shomi75]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

I had the same problem. Resolved with replacing two led stripes. Before I had 120v on led and now it is about 160v

[ReeceyBurger123]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

Any update ? I had same issue with VES390 other day Leds very dim J60 output resistor was nearly OC it was physically burnt. I stole one off another board I did not get its value though.

[flocko]

Re: JVC LT-40DJ51J - Vestel 17IPS20 - LEDs very dim

J60 is a plain jumper wire, what have you been putting in that vape of yours?