LG 32LD350 Power light goes blue for 10-15 secs then flashes red

[dicky96]

Hi Guys
I did a quick forum search and found some posts about this model but not the fault I have

First of all - this TV has been dropped, not from a great height but a few feet to land on one front corner. It stopped working after that.

There is no obvious damage to the casing, screen or PCBs or loose connectors that are noticeable

What happens is that when plugged in the power LED lights up red. Press the Standby button and it goes blue for maybe 10-15 secs then starts flashing Red

On the PSU there is a connector with the various pins marked (see pic)

What I get is (While the blue power LED is on):
All voltage rails (3.5V, 20V, 12V) are present and correct.
The pin marked Power -On has 3.25V on it
The pin Marked Error alternated 3.4V -> 0.6V -> 3.4V -> 0.6V several times, slow enough to see on my DMM

Then once the Power LED starts flashing Red I get:
Voltage rails only the 3.5V is present
The pin marked Power -On has 0V on it
The pin Marked Error 0V

Pressing the Standby Button starts the whole sequence again

Any ideas on this one?

Cheers
Rich

[vinceroger69]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

service manual

[dicky96]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

Ahhhh ... found an Interconnect Diagram and schematic from another thread here regards this model

Unfortunately my PSU does not seem to match the one on the Interconnects diagram but it would seem the TV is trying (and failing) to turn on the back lights). Got the schematic from another thread but they seem to have ommited the PSU diagrams!

Checked the voltage between the grey wire and the two pink wires (which are connected together) that feed the back lights and nothing there. Just spotted an open circuit fuse on the PSU in the area of the backlight output connectors. Will investigate further........

Rich

[vinceroger69]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

dont measure the back light voltage with your multi meter as its very high as most meters cant go that high i cant remember the exact figure but someone will advise.
whats the full model number as there are a few manuals the one i linked is for the ua version of your set

[budm]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

Firing Voltage is about 1500~2000 high frequency AC!
The question is do you see the backlights even flash on for seconds if you look at the back side of the LCD panel.
BL-ON DCV is ?????

[vinceroger69]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

Firing Voltage is about 1500~2000 high frequency AC!
The question is do you see the backlights even flash on for seconds if you look at the back side of the LCD panel.
BL-ON DCV is ?????

Thanks budm i new ccfl/eefl invertors output voltage was high but didnt no it was that high certainly enough to damage a meter etc.

[dicky96]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

OK thanks guys. There is no HT as the 16A fuse is blown. Traced it out a bit - input end of fuse goes to +ve on main smoothing caps of SMPS so should be feeding 350VDC approx via the fuse to HV inverter.

Other end of fuse goes to the 2SK3868 MosFETS - four of them on one heatsink. Think probably connected as two pairs driving high side and low side of output ransformers (just a hunch). Source of two of the MosFETS goes to the -ve end of main smooting caps. No short circuit from MosFET end of blown fuse to -ve of smoothing caps, no shorts around MosFETS so no obvious reason why fuse has blown at the moment. Checked for short across leads going to backlight.... nope.

Visually checked PSU PCB for cracks, fractures etc - nothing obvious.

Where do I measure BL-ON DC Bud? there's not a pin marked as that on the output connector from PSU to main board.

Rich

[vinceroger69]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

i think its inv on off

[dicky96]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

Oh, full model number = 32LD350ZA

[budm]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

This is your board, right?
LG EAY60869102 (EAX61124201/15)

Pictures provided by shopjimmy.

[dicky96]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

INV ON OFF does 3V...... 0,6V.....3V....0.6V....3V.....0.6V/.....0V

Think maybe I should just replace the fuse and see what happens. Unfortunately I don't have any suitable ones here in Gran Canaria but am returning to UK for 18 days on Monday so could bring some. Would be nice if I had my variac and mains isolation transformer here to but they are two heavy to carry unless it is really worth my while. Same goes for my trusty analog Techtronix scope.

I could replace the fuse with something like a 100W light bulb and fire it up just to see if the inverter oscillates- that's an old trick I use when working on suspect SMPS or big audio amps that are likely to go BANG. Seems the worse that would happen is the bulb lights up - Any thoughts on that?

Rich

[dicky96]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

@budm sorry crossing posts in the night here lol. Yes that's the one.


Oh sorry no/. It looks like that but it is a 201/14 not 201/15

[budm]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

So for sure that there is no low resistance readings between Drain and Source pins all 4power MOSFETs driving transformers, and the blue small disc snubber caps in that section all OK?
Fuse that high of current rating to blow the current draw was very very high.

[dicky96]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

FIXED.

I really couldn't see any low resistance readings around the Inverter Drive so I (as a temporary measure) got a 13A mains fuse as I didn't have the correct 16A one and soldered a couple of wires to it from the PCB.

The backlight then comes on and the TV works fine

My humble opinion - as I stated originally this TV had been dropped, it was not connected to mains at the time. It is possible the physical impact caused the wire inside the fuse to break rather than the fuse blowing in the normal elecrtical sense?

When I bring some more kit over from the UK in a few weeks I will bring my small bench vice to hold the 'blown' fuse and cut it open with my dremmel. I'll bet once I look inside it has not 'blown' per se.

Anyway TV working, awaiting correct fuse on my return

Rich

[dick_barton]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

Are you certain that it's a 16 amp fuse and not a 1.6 amp fuse. Seems awful high value to be in a TV set!!!!

[dicky96]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

It does doesn't it. You can see it on the pic of the psu (component side) that bud uploaded - top right, next to two big inductors - fuse has two stripes on it. Below that you can make out F3 16A though it looks more like 15A on the pic from bud

So it's marked on the PCB as 16A but just looked on the actual fuse and it is actually a 3.15A!!! Still don't have one here though so will have to wait until I bring more kit back with me from UK

Ahh I see now it is saying on the pcb 'F3 15A' as a rating (without the decimal point) not the component F3 rated 16A lol

[dick_barton]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

F3. 15Amp is a 3.15 amp fuse. Poor spacing between digits.

[budm]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

Since the TV was dropped, you should look for hairline crack on that power supply board just in case there is intermittent connection in that Inverter section.

[dicky96]

Re: LG 32LD350 Power light goes blue for 10-15 secs then flashes red

@budm

Will do bud - I have already had a look under my bench magnifier but will try flexing the board very slightly under the magnifier and see if there is something I missed

@dick barton. Yes agreed mate, as I said the fuse is rated 3.15A when I examined the fuse itself. The spacing between digits on the screen printing is very bad. What also threw me is the fuse is physically large, not like your normal 3.15A in line fuse. Will look out for anything like that in future

Back to the UK now for a couple weeks, gotta deal with some business as we are trying to sell up there. Can't wait to get back to Gran Canaria and it's sunshine, beaches and At least I can bring more of my electronics kit back with me

Cheers
Rich