17ips20 diagnosing

[formant84]

Re: 17ips20 diagnosing

Yeah I'm an idiot. I was testing them wrong. Turns out there are 4 duds.

Not only that but I have some SMD LEDs that should be close enough to use. Gonna replace them now, I'll post the results.

Thanks for the advice!

[formant84]

Re: 17ips20 diagnosing

Replaced the dead LEDs, powered on... Still no backlight.

My guess is that my replacements couldn't take as much current as the originals and just instantly died. Got no more time to look at it today, might order the LEDs you linked in and have another stab at it during the week.

Thanks again.

[formant84]

Re: 17ips20 diagnosing

Turns out the new LEDs are fine. They all flash once just as the voltage goes up to 190 but then go off straight away before it settles down to 115v. Any ideas?

[formant84]

Re: 17ips20 diagnosing

I Assume the LEDs are powered from a constant current source which isn't working, giving them a spike and then virtually nothing. I've tried measuring the current with my multimeter and it's either around 1ma or the fuse in my multimeter has blown :/

[vinceroger69]

Re: 17ips20 diagnosing

have you retested all the leds again one by one? ive just fixed a strip for someone who had fitted some of the new leds on the wrong way anode/cathode as he didnt notice the pad size diffrence on the leds.

[ReeceyBurger123]

Re: 17ips20 diagnosing

have you retested all the leds again one by one? Ive just fixed a strip for someone who had fitted some of the new leds on the wrong way anode/cathode as he didnt notice the pad size diffrence on the leds.

+1

[formant84]

Re: 17ips20 diagnosing

Yeah tested every one, and like I said they all flash on for a split second as the voltage jumps to 190v, so they're all working.

[dick_barton]

Re: 17ips20 diagnosing

Unfortunately leds flashing on doesn't really test the leds since it's only momentary. You may be better off testing them with an external power supply that you can current limit initially at 50mA or if you don't have a power supply then perhaps carefully with batteries.
There are threads on the Forum discussing methods.

[formant84]

Re: 17ips20 diagnosing

Yeah like I said the first two times, I have tested all of the LEDs individually and they're all working.

[crt man]

Re: 17ips20 diagnosing

Hi
When you tested them individually, did they all have the same brightness?
I had a strip that when tested, they were duller than the others,
so there was a fault within that particular strip.

Alan

[formant84]

Re: 17ips20 diagnosing

Hi Alan,

Well the ones I've replaced are a slightly different brightness, they aren't the exact right ones but I would have thought that as long as they light up and don't blow they would be okay. I guess this is not the case?

Do you think this is most likely to be the problem, or is it still possible that a fault on the power board is resulting in a shortage of current to the LEDs despite the correct voltage being supplied?

Thanks,
John

PS: Dick, sorry for being short with you, this TV is just winding me right up!

[vinceroger69]

Re: 17ips20 diagnosing

my guess its the leds you have replaced maybe upsetting the led ouput feedback circuit? are your replacement leds brighter or darker in brightness?
what tv is this your working on?

[formant84]

Re: 17ips20 diagnosing

It's an ISIS 39227FHDDLED. Similar chassis to other cheap TVs with this vestel board.

The new LEDs are dimmer.

Is there any safe way to bypass the relevant LEDs to see if the backlight comes on?

[vinceroger69]

Re: 17ips20 diagnosing

im not sure about bypassing them but this link is for vestel leds
http://www.ebay.co.uk/itm/VESTEL-VES...3D252304716100
not sure what postage is on these from ohm supplies
https://shop.strato.com/epages/62027...ts/LED11-Y6.01

[formant84]

Re: 17ips20 diagnosing

Thanks, I'll give them a try when i can spare a few quid.

[vinceroger69]

Re: 17ips20 diagnosing

ive not tried either of these leds myself but they do say for vestel tvs i have used ohms supplies before for parts and they have always been good so do recomend there shop if postage is cheap 1.95 for 10 leds isnt bad i guess.

[smiddy1980]

Re: 17ips20 diagnosing

Hello, sorry for jumping on here but I have a 17IPS20 that the power going to the main board jumps from 23.3 down to 15 when the main board is plugged in, when I unplug the main borad the voltage sits at 23.3, I don't get any other voltage on the pins going to the main board, show I not see a 5v? do you think this is a faulty PSU or main board ?

Thanks Guys

[vinceroger69]

Re: 17ips20 diagnosing

The best way would be to force on the psu by itself and place a load on the psu outputs and see if its ok and the voltages stay stable under the correct load