"Dick Smith" 55" LED backlight issue - model GE6880

[nomoresonys]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

Nice work FamilyMan.

[chrise]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

Hi, I know this is an old post but I am having the same issue. I cannot find the schematic for the board mentioned and the link in the first post no longer works. Does anyone have a schematic they could share with me?

[budm]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

Hi, I know this is an old post but I am having the same issue. I cannot find the schematic for the board mentioned and the link in the first post no longer works. Does anyone have a schematic they could share with me?

Luckily I download and save the file.

[chrise]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

Thanks budm, you're a life saver

[chrise]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

I am trying to figure out what is wrong with my power board and I noticed Q111 is completely missing from the board. There appears to be solder from where one may have been attached. Does anyone know if this is present on the boards you have worked on? Hoping that possibly someone has some pictures or an old board laying around they could peek at.

[nomoresonys]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

Some images there, might help, that's if your model number is same as the OP: https://www.google.com/search?q=GE68...w=1280&bih=645

[dkneyle]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

I've currently got two of these in with identical fault. I've followed this thread for advice.
I changed the snubber diode (which did not measure any resistance fail) as others reported. Changed out with a 600V fast recovery snubber I had on hand without any luck.
Then I started to look at Family Man's post about the TL432 device. Now what I can't understand is why use a TL431 and TL432 in different parts of the circuit. My reading of the datasheets and elsewhere suggests they are interchangeable, adjustable down to about 2.5V. So why specify two different types on the schematic and why then substitute a different part?
I've got a heap of new TL431s on hand, so I might experiment and see what happens.
Of course, it might too be that I have failed LEDs in both TVs (highly likely) and I'm going up a dry gulch with all of this?
(I think I'll invest in a backlight tester - especially given how often I want to know if I have faulty backlights - probably beats having to pull the panel apart.)

[dick_barton]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

TL431 can maintain a constant current of 100mA and TL432 of 50mA

[dkneyle]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

TL431 can maintain a constant current of 100mA and TL432 of 50mA

Thanks Dick for your input.
Which then doesn't really explain how FamilyMan's workaround got his SMPS operational, since it isn't really anything to do with voltage thresholds?
And from a manufacturing viewpoint, why specify TL431 on one part of the circuit and TL432 on another, since they are basically the same device? And then why substitute TL432 with another part rather than TL431, since they are obviously available to the manufacturer as they have been used elsewhere on the board. All very weird.
I've ordered one of these new clever constant current output LED testers. I'm pretty sure I'm going to find I have failed LEDs rather than any problem with the PSU. These cheap re-badged Chinese TVs use inferior panels and I know from past experience the LEDS do not last. But as I've got two TVs I can salvage some LED strings and swap and get at least one going. I'll update this post to assist other Aussie's who are trying to repair these Dick Smith TVs.

[dkneyle]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

Yes, in my case it turned out to be a failed LED rather than power supply issue.

Anyone following my post in this thread, here are my thoughts. These VERY CHEAP DSE/Kogan TVs use really cheap and nasty low grade panels. I shorted out the dud LED to get the panel operational again. When I did so we had a vertical line. Obviously the panel surgery had caused a panel contact to slightly come away (even though we'd been as careful as we could in performing the operation). A slight tweak of the panel and it comes good, another tweak in the opposite direction and it's back again. No strength in the frame whatsoever.
The colour rendition is woeful. Reds are more a magenta. Greens are a lime-green. (I've had this with other Kogan TVs and I've actually sent them back for a refund because they look so bad.)
My advice? Scrap the TV. That's what I did today with the second one. No point wasting time trying to get it operational. Advertised the boards for sale as second hand parts.
By the way, identical model numbers, but different T-Con and LED strips. Probably entirely different panels.

[nomoresonys]

Re: "Dick Smith" 55" LED backlight issue - model GE6880

Good point dkneyle, nothing worse than a tv that can't even produce decent color, not worth messing with.

[dagav]

Have gone trough the thread, and tried to find some tip, for the JVC - LT-50E73, without luck. Despite the rather old thread on TV5001-zc02, I hope some can give some clue about a JVC - LT-50E73 TV stuck in stby,(no reaction either on remote or buttons on TV), and with no backlight, with this powerboard inside. Voltage missing on the main connector is on/bk. On Led connectors voltages are 0, on all outputs, and no difference if they are connected or not. My ledstrip tester says 300V, open circuit, on both strips, so they are faulty. But can it also be a faulty motherboard since the TV is stuck in standby?

[dkneyle]

Have gone trough the thread, and tried to find some tip, for the JVC - LT-50E73, without luck. Despite the rather old thread on TV5001-zc02, I hope some can give some clue about a JVC - LT-50E73 TV stuck in stby,(no reaction either on remote or buttons on TV), and with no backlight, with this powerboard inside. Voltage missing on the main connector is on/bk. On Led connectors voltages are 0, on all outputs, and no difference if they are connected or not. My ledstrip tester says 300V, open circuit, on both strips, so they are faulty. But can it also be a faulty motherboard since the TV is stuck in standby?

Dagav, if your LED tester says the panel LEDs are busted, then what is the point of going further? Those testers are pretty good at firing the LED string if there's nothing wrong with them. From what you have described, I'd certainly also suspect a failed mainboard if you aren't getting any turn backlight on voltage signal. I assume you have +5v standby supply?

[dagav]

+5V stby ok