17ips20 diagnosing

[layad]

hello guys
i have led tv which has 17ips20 psu , the tv is completely dead , no lights at all, i have checked the all the diodes, they are all ok, all fuses are ok, anyone knows how to test Q301? the tv is jvc le-40dg51j
thanks

[zwarder]

Re: 17ips20 diagnosing

There are kits available to repair

http://www.ohmsupplies.co.uk/KIT377-...D13-REPAIR-KIT

Probably pick up a second hand board cheaper though

[ReeceyBurger123]

Re: 17ips20 diagnosing

Normally there is a leaky not shorted diode right next to the filter caps. Remove it out of circuit and check it for continuity in both directions common issue on these boards. If the transistors fail they will blow the fuse.

[crt man]

Re: 17ips20 diagnosing

Sorry Reece for hacking the thread,but I got a Hitachi
40 inch Led from somebody's garden with the above PSU.
Which is the leaky diode you mention,as there is no shorts
on the FET's and the fuse is fine.

I cannot see the diode you mention or I'am I just going
senile with old age.

Thanks Alan.

[vinceroger69]

Re: 17ips20 diagnosing

reece has a good video about this board not sure if you have saw it
https://www.youtube.com/watch?v=x7vnoqcTbQM&app=desktop

[crt man]

Re: 17ips20 diagnosing

Hi
Yes I have seen it but this has not blown up,
and the are no obvious shorts.
I assume it is the leaky diode he is talking
about in P3

Alan

[vinceroger69]

Re: 17ips20 diagnosing

im sure reece will reply when he sees this thread and advise you on the diode location

[ReeceyBurger123]

Re: 17ips20 diagnosing

Cheers Vince, also what is the set doing totally dead ? You should check ehat voltage you have on the secondary diodes first see if you have 12v at the lower down ones then 12-128v at the ones near the top. If so then psu is good.

[Andrew F. Ali]

Re: 17ips20 diagnosing

If I may inject here....I have found that analogue meters detect 'leaky' semi-conductors more readily than digital meters. I have a trusty analogue on my workbench for testing semis

[crt man]

Re: 17ips20 diagnosing

Cheers Vince, also what is the set doing totally dead ?

Sorry Reece, I was told set did not work,
as it had been standing in the rain I did not plug it in.
Just plugged it in and led changes from red to blue
but screen is black and no sound, I do not have the
remote so it could be on an external source.

Alan

[ReeceyBurger123]

Re: 17ips20 diagnosing

Well the Psu is good then, you have an Led failure probably. Watch this video:

https://m.youtube.com/watch?v=RxwdC7V5Ue0

Please verify if you have backlight or not, if you do not check the Led voltage, if that is good take the panel apart and check the backlights as shown in the video. Be very carefull with the Lcd screen and its attached Pcb they are easy to break and wont be fixable if so. Keep us updated

[crt man]

Re: 17ips20 diagnosing

Please verify if you have backlight or not, if you do not check the Led voltage,

Reece, the backlight is out i hooked up a free view recorder
and it switched to the scart.
There was sound, and when turned to the window
an image was visible

The voltage for the LED's was 119 on positive and 11
on negative.
I have bought some Nos LED's from Ebay just waiting for
them to arrive

Alan.

[ReeceyBurger123]

Re: 17ips20 diagnosing

Wait on start up does the voltage go to about 170 or so then go down ? If it stays at 119 your Psu/driver is faulty.

[crt man]

Re: 17ips20 diagnosing

At start up the power goes to 190 before
dropping back to 119 the negative goes
to 24 then drops back to 11

On standby the voltage on the positive drops
to zero and the negative stays at 11

Alan.

[ReeceyBurger123]

Re: 17ips20 diagnosing

Yes then you have a backlight fault then, the Psu is fine if it goes up then drops. Take the panel apart and test the Leds as shown in the video.

[Leslie W]

Re: 17ips20 diagnosing

Hi Guys

Hitachi 42hxt12u with Vestel 17ips20 23145840 problem.

TV made a crack noise and now no picture. No backlights but I can see menu with torch.

Audio working and can change channels and sources.

LED output from PSU is 117.7 return 8.3 when turned on - it does not go to 170 or 190

Is this a psu or a led problem? Why arent the leds lighting if I have 118 volts for the 36 x 3.3v vor the leds?

[ReeceyBurger123]

Re: 17ips20 diagnosing

Unplug the Leds and check again, use chassis ground. Sounds like a Psu problem to me if it stays low. Also thats not enough for the Leds that voltage its enough to complete the chain but only light them dim.

[Leslie W]

Re: 17ips20 diagnosing

Hi Reece

Thanks for your help, please bear with me I am just a beginner.

Why does the led voltage start at 160+ then go to 118 if 36 x 3.3 leds = 118 volts ?

with the leds unplugged voltage is 117.6 and zero on return

Les

[ReeceyBurger123]

Re: 17ips20 diagnosing

Its part of the Pwm circuit, starts at higher voltage to start the strings but low current, the it lowers and increases the current to maintain proper brightness whilst the Pwm is working. Your Psu is faulty in your case.

[Leslie W]

Re: 17ips20 diagnosing

Thanks Reece

Just ordered one from ebay.

If it works I could send you the old one.

Cheers

Les