Hitachi LE55A6R9A - No backlight

[Tron guy]

Re: Hitachi LE55A6R9A - No backlight

If you believe that you have 270V at the led connector of which they appear to be wired in series then I believe that you may well have an open circuit led.

I definitely had 270vdc at CN 202.

So when you say "open circuit led"

are you saying a single LED or strip is bad?

Or is my voltage so high that a diode or transistor went out on the power board?

Again when watching a few videos I determined I had +12vdc at all of the points listed between the boards, +5vdc as well where it was supposed to be.
Shining a flashlight on the screen when powered on, got me some image in menu mode.
I am an absolute newbie at led/lcd tv repair (first attempt here).

thank you for replying

[dick_barton]

Re: Hitachi LE55A6R9A - No backlight

If you believe that you have 270V at the led connector of which they appear to be wired in series then I believe that you may well have an open circuit led.

[Tron guy]

Re: Hitachi LE55A6R9A - No backlight

Have you read through the thread and carried out any of the tests suggested earlier in the thread?

It seems like most of the thread is attempting to determine if his meter works. ��

If i remember correctly, the positions CN202 and CN203 , i was getting something like 270vdc out of 1, and a few vdc from the other.

I'm have not purchased an led tester (and probably won't).
I do believe, based on watching shopjimmy video(s) , that the power, t-con, and main board are all good.

[dick_barton]

Re: Hitachi LE55A6R9A - No backlight

Have you read through the thread and carried out any of the tests suggested earlier in the thread?

[Tron guy]

Re: Hitachi LE55A6R9A - No backlight

I'm bot sure what the thread etiquette is on this forum so if I have breached it with this post, I apologize in advance. I'm bot sure if I can even start threads yet.

Anyway, I have the same tv as the OP of this thread. As far as I can tell (watching youtube vids), all 3 of the main boards in my tv are good.
It has sounds but no video.

The flashlight test shows me images very light when I hit the menu button.

I now find myself still unsure how to proceed. It sounds like my 2 potential issues are:
Led inverter board or
Led strips themselves

So, do I just buy both and go with it? I prefer to be a cheap-a$$ when possible.

Also, is it an absolute must to buy specific led strip "kits" specific to each model tv, or can I just sub in some led strips I picked up on ebay for $10. These particular ones run off of 12vdc I believe.

A little about me, I am a competent arcade monitor (crt) repair guy, and overall good at repairs on arcade games and pinball machines.

I certainly encourage input, and will not be offended easily.

[mmartell]

Re: Hitachi LE55A6R9A - No backlight

Car battery ? How about a simple 9v or AA even.

[PorkfriedPanda]

Re: Hitachi LE55A6R9A - No backlight

The led tester will allow you to test each led strip or individual leds to verify which leds are faulty or show up any led strip connection problem. However it does mean removing the led panel carefully.

Of course, that's what I'm studying up to do.

I'm considering buying the little dedicated ShopJimmy gizmo to detach the single LED, and maybe some LEDs and diffusion covers so I can do this again if I have to.

And don't forget to test your meter !

Definitely. I keep forgetting to do that, next time I've got a little spare time I'll unhook a car battery and check it.

[mmartell]

Re: Hitachi LE55A6R9A - No backlight

And don't forget to test your meter !

[dick_barton]

Re: Hitachi LE55A6R9A - No backlight

The led tester will allow you to test each led strip or individual leds to verify which leds are faulty or show up any led strip connection problem. However it does mean removing the led panel carefully.

[PorkfriedPanda]

Re: Hitachi LE55A6R9A - No backlight

Bought the LED tester, confirmed that bottom LED strip works, top LED strip doesn't.

Exploring options from here, watching vids, etc.

Thanks for all the info guys

[PorkfriedPanda]

Re: Hitachi LE55A6R9A - No backlight

I'll make the orders soon, but I may have to wait a few weeks with the holidays and all.

In the meantime, a question. The LED tester can be used to test the strips prior to opening the chassis and messing with them, yes?

I'm not super hung up on saving this TV, more interested in practice, so I'm not opposed to opening it up. Still, if this particular unit can be salvaged without risking damage that's a plus. And I can, of course, practice that on a different TV in the future.

[budm]

Re: Hitachi LE55A6R9A - No backlight

Fair enough. What's the cost for the LED tester, if it's not outrageous I wouldn't mind picking it up. Probably won't be the last time I try to fix a TV, honestly.

This seem right? https://www.amazon.com/0-310V-Output.../dp/B01A1479ZS

EDIT: Can anyone recommend a not-outrageously-expensive but adequate multi-meter for this kind of work?

That is a good tester to have.
Car 12V will be fine to see if your meter is still working or not.

[R_J]

Re: Hitachi LE55A6R9A - No backlight

That is one, check around there may be others cheaper, there were posts on here about them somewhere. I think they are around $30.00
heres one http://www.ebay.com/itm/0-300V-LED-L...t_11251wt_1036

This is the model SID-GJ2C

[PorkfriedPanda]

Re: Hitachi LE55A6R9A - No backlight

It could be a bad power supply but it could also be an open led in the panel. I have seen more problems with bad panel led's but you would need to check them, they make a small led tester for that purpose.
Thats about all I can do from this far away.

Fair enough. What's the cost for the LED tester, if it's not outrageous I wouldn't mind picking it up. Probably won't be the last time I try to fix a TV, honestly.

This seem right? https://www.amazon.com/0-310V-Output.../dp/B01A1479ZS

EDIT: Can anyone recommend a not-outrageously-expensive but adequate multi-meter for this kind of work?

[R_J]

Re: Hitachi LE55A6R9A - No backlight

It could be a bad power supply but it could also be an open led in the panel. I have seen more problems with bad panel led's but you would need to check them, they make a small led tester for that purpose.
Thats about all I can do from this far away.

[PorkfriedPanda]

Re: Hitachi LE55A6R9A - No backlight

You need to find out if your meter is good and working or not first, wrong data will not help troubleshooting the problem.
If the meter is good then we need to find out if the LED driver circuit is getting the BL-ON signal to turn on that power section on or not and go from there.

You said 12v right?

Is a car battery a safe test?

[budm]

Re: Hitachi LE55A6R9A - No backlight

You need to find out if your meter is good and working or not first, wrong data will not help troubleshooting the problem.
If the meter is good then we need to find out if the LED driver circuit is getting the BL-ON signal to turn on that power section on or not and go from there.

Hitachi 850118727 Power Supply
http://www.shopjimmy.com/hitachi-850...wer-supply.htm

BTW, your meter does not have that high of the frequency bandwidth to measure high frequency AC Voltage.

Pictures provided by shopjimmy.

[PorkfriedPanda]

Re: Hitachi LE55A6R9A - No backlight

You would need to connect the probes where I indicated and then turn on the tv, Its a good chance that if there is no load (ie: open led circuit) the power supply for the led's will shut down. so the voltage may only be there for a couple seconds

Gotcha, I'll try that now!

EDIT: Okay, tried it. Powered it off and on and even turned it off and on at the wall once with the probes in place while staring at the meter. Nothing across there.

EDIT2: I'll get you that larger view, by the way. Sorry I think I missed an edit, and I read that about it being isolated from the chassis ground as well!

EDIT3: Actually, copied over from budm's ShopJimmy link!

[R_J]

Re: Hitachi LE55A6R9A - No backlight

You would need to connect the probes where I indicated and then turn on the tv, Its a good chance that if there is no load (ie: open led circuit) the power supply for the led's will shut down. so the voltage may only be there for a couple seconds

[PorkfriedPanda]

Re: Hitachi LE55A6R9A - No backlight

If he measured high voltage on the anode of the diodes, that could be correct as the spikes could be quite high and at a high frequency the meter may give a false reading.
Thats why I say to measure the dc voltage accross the two points I indicated

TV is on with the light blue. Pressing metal to metal in the socket, set to DC voltage 200, with the probes set correctly and measuring with the probes precisely where you show...

I get nothing on the meter. Bad power board after all?