LG Flatron L17NT-A no power

[fsearcy2]

Re: LG Flatron L17NT-A no power

Ok Plainbill,
if i knew what i was doing i wouldn't be on here..:-) <bk>
i will try to be more precise from here on out <bk>
i crossed the filter @ junction C101 and got 160.8 dcv <bk>
@ connector CW201 pin6 =5 dcv. and pin7= 5 dcv , pin10=13.78 ,pin 11=13.78. <bk>
8pin ic @ U101 i jumped pin 1 and 5 and got 115 dcv. <bk>
thats how i determined the power board was in good shape. <bk>
now for the logic board the parts you circled.<bk>
U202= 3 TERMINAL LOW DROP OUTPUT VOLTAGE REGULATOR part#kia78D33F
i had 4.4 dcv going in and 3.0 coming out.<bk>
U203= PART#LD18 it is a 3 prong surface mount made by STmicro but could not find a data sheet or that part either? but i had 3.0 dcv on pin 3 and 1.5 dcv on the drain. <bk>
U407= 3 TERMINAL LOW DROP OUTPUT VOLTAGE REGULATOR #Kia78D33F i had 3.4 dcv. in and 2.1 dcv. out.

datasheet.

[fsearcy2]

Re: LG Flatron L17NT-A no power

KIA78D33F DATASHEET

[PlainBill]

Re: LG Flatron L17NT-A no power

Ok Plainbill,
if i knew what i was doing i wouldn't be on here..:-) <bk>

I sometimes feel the same way myself.

i will try to be more precise from here on out <bk>
i crossed the filter @ junction C101 and got 160.8 dcv <bk>
@ connector CW201 pin6 =5 dcv. and pin7= 5 dcv , pin10=13.78 ,pin 11=13.78. <bk>

Those voltages look good. 13.78 is a little high, but that would be normal if the backlight was off.

8pin ic @ U101 i jumped pin 1 and 5 and got 115 dcv. <bk>
thats how i determined the power board was in good shape. <bk>
now for the logic board the parts you circled.<bk>
U202= 3 TERMINAL LOW DROP OUTPUT VOLTAGE REGULATOR part#kia78D33F
i had 4.4 dcv going in and 3.0 coming out.<bk>

That output seems a little low, as does the input.

U203= PART#LD18 it is a 3 prong surface mount made by STmicro but could not find a data sheet or that part either? but i had 3.0 dcv on pin 3 and 1.5 dcv on the drain. <bk>

LD18 rings a bell. I'l do a little checking.

U407= 3 TERMINAL LOW DROP OUTPUT VOLTAGE REGULATOR #Kia78D33F i had 3.4 dcv. in and 2.1 dcv. out.

I may have given you some bad advice. If you would, check the input and output voltages of the three regulators with the black probe on the tab of the regulator. Those input and output voltages are low. I would expect one or more of 3.3V, 2.5V, and 1.25 V out of the regulators.

Also, would you take a bigger picture of the logic board. I'd like to see the complete board, as well as more detail. I want to see where the panel gets power.

PlainBill

[fsearcy2]

Re: LG Flatron L17NT-A no power

regulator U202-pin-1 (4.4) pin-3 (3.0)
regulator U203-pin 1-(1.6) pin 2 -0 pin-3 (1.5)
regulator U407- pin-1 (3.58) pin-3 (2.1)

[PlainBill]

Re: LG Flatron L17NT-A no power

Okay, so I finally got around to getting up the list of my caps.
I'm not too familiar with the markings, so I'll include everything.
There are 8 total, as you mentioned.
They are all Samxon, all 105°C6, and all GF(M) unless otherwise noted:
(2) 1000μf, 25v, V5A, 10mmx20mm
(2) 1000μf, 16v, C6A, 10mmx20mm
(1) 680μf, 25v, V4A, 10mmx20mm
(1) 470μf, 25v, V4A, 10mmx15mm
c103: 33μf, 50v, V5A, GF(M), 7mmx12mm
c105: 0.47μf, 50v, V5A, KM(M), 5mmx10mm

Does that give you what you need?
I'm going to try looking them up again now, but I wasn't having much success last night, so your help would be appreciated.
Thanks!
Elmojo

A few points: The ESR rating, identified by looking up the series, is more a measure of performance rather than a value to match. If the original has an ESR rating of .08 we don't want to choose a substitute with a rating of .12 (although that might work, at least for a while), but ratings of .08, .06, or even .02 don't present a problem. Also, while knowing the location of the original is important when installing the replacements, they don't help me select the appropriate parts. Last, often the proper value is not available in a particular case size. In those cases it helps to know the maximum height that can be accommodated. So here's my suggested replacements; I've tagged any with different dimensions.

(2) 1000μf, 25v, 10mmx20mm* P12379-ND EEU-FM1E102 @$0.76 *
(2) 1000μf, 16v, 10mmx20mm P12366-ND EEU-FM1C102 @$0.59
(1) 680μf, 25v, 10mmx20mm 565-1551-ND EKY-250ELL681MJ20S @$.52
(1) 470μf, 25v, 10mmx15mm P12388-ND EEU-FM1E471 @$0.50
(1) 33μf, 50v, 7mmx12mm P10320-ND EEU-FC1H330 @$.27
(1) 0.47μf, 50v, 5mmx10mm 493-1885-ND UPW1HR47MDD @ $.34

* The 1000uF, 25V has a diameter of 12.5mm

PlainBill

[PlainBill]

Re: LG Flatron L17NT-A no power

regulator U202-pin-1 (4.4) pin-3 (3.0)
regulator U203-pin 1-(1.6) pin 2 -0 pin-3 (1.5)
regulator U407- pin-1 (3.58) pin-3 (2.1)

OK, I'm baffled. Those voltage definitely are lower than I would expect.

HOWEVER, take a look at this thread.

PlainBill

[fsearcy2]

Re: LG Flatron L17NT-A no power

could it be that i dont have it hooked up to the screen?
and i also dont have the back lights hooked up.

i do have a question shouldnt i be getting some kind of power out of the back light terminals?

i also looked at the thread you sent to me and im not sure what you want me to see?

thank you anyway for your help.

[PlainBill]

Re: LG Flatron L17NT-A no power

could it be that i dont have it hooked up to the screen?
and i also dont have the back lights hooked up.

I don't think so. Usually when a power supply doesn't have a load the output goes high. As far as I can see, the regulators on the video board get their power from the +5 volt power supply. But it reads only 4 volts.

i do have a question shouldnt i be getting some kind of power out of the back light terminals?

Not unless the processor on the logic card is working.

i also looked at the thread you sent to me and im not sure what you want me to see?

thank you anyway for your help.

The guy had a SIMILAR problem. The cause was a bad crystal.

PlainBill

[starmaker60]

Re: LG Flatron L17NT-A no power

it is so so easy to solve
i fixed more than 10 of this model
there is only one cap is bad 1000/16 just change it and it will turn on directly

[fsearcy2]

Re: LG Flatron L17NT-A no power

i will give it a try i have done everything else so far with no results

[sceva]

Re: LG Flatron L17NT-A no power

it is so so easy to solve
i fixed more than 10 of this model
there is only one cap is bad 1000/16 just change it and it will turn on directly

I have an LG Flatron L1952 with the same symptoms. I have an esr meter, and checked all the caps. Like the quote, I only found one bad cap. I wanted to let you know the location, but I forgot to write it down before reassembling. It was 1000/16 and slightly bulging.

[Scenic]

Re: LG Flatron L17NT-A no power

i've got a LG L1952HQ here.
there are only 2x 16V 1000uF caps in there.
all caps are samxon GF though, so only replacing the single bad one isn't gonna last long.

[fsearcy2]

Re: LG Flatron L17NT-A no power

I have an LG Flatron L1952 with the same symptoms. I have an esr meter, and checked all the caps. Like the quote, I only found one bad cap. I wanted to let you know the location, but I forgot to write it down before reassembling. It was 1000/16 and slightly bulging.

ok thank you i will look at it again i have checked them all once but will do again.

[Magnethead]

Re: LG Flatron L17NT-A no power

I have an LG Flatron L1952 with the same symptoms. I have an esr meter, and checked all the caps. Like the quote, I only found one bad cap. I wanted to let you know the location, but I forgot to write it down before reassembling. It was 1000/16 and slightly bulging.

My LG Flatron L1932TQ (throwing google a bone here) quit getting power, so I opened it up. I got 165V out of the bridge rectifier, but zero volts DC or AC out the back side of the PT-002134-2 2650C0062. After seeing this post, I started hunting down capacitors, Sure enough, One of the 1000/16's (C204, in front of the 3 and 5 volt regulators on the common heatsink bar) is bulding out the top. Thankfully I live 3 blocks from Mouser Electronics, so replacement will be simple.

Using bolt hole/grounding pad PG2 as a ground reference, I currently get a sinking 12 (or 9, or...depending on when you measure it) volt measurement on 3 pins (last 3 i believe), with AC plugged in.

I shall report back after cap replacement.

[oktopusprime]

Re: LG Flatron L17NT-A no power

OK first of all great site! it's always good to have a place to look for help when things go bad.

My problem is my lcd went dead. it's a flatron pcb inverter board that i used with a microtek 17" lcd coz the microtek board died too.



caps removed:
c202,c206: 1000uf 25v
c203: 680uf 25v
c204,c205: 1000uf 16v
c207:470uf 25v
c103: 33uf 50v
c105: 0.47uf 50v

i've removed the big green caps although i just found 1 bulging cap(c204).

i also removed c103 & c105 and noticed a black carbon residue on the base of the caps.

the biggest cap measured something like 336Volts.

i'm buying the replacement caps first thing in the morning and see if i can make this thing work again.



look at that! a ferrite bead? FB101 blackened around the sides and some black carbon residue on the base..
is it toast? how can i replace that?

[selldoor]

Re: LG Flatron L17NT-A no power

Some members including myself would prefer pictures posted using manage attachments. Whilst yours load quickly they do not enlarge much.
You can test a ferrite bead - same test as a fuse - meter on ohms 200
should show the same as touching probes together.
You can buy them? If it is open then perhaps you can take it to bits and then thread the beads onto a new wire.

[oktopusprime]

Re: LG Flatron L17NT-A no power

Woohooo! i replaced all caps and it works again!! thanks to all!

ps. sorry for the un-managed images. i'll post managed next time

[selldoor]

Re: LG Flatron L17NT-A no power

Well done - another saved and second time round, very commendable.

[oktopusprime]

Re: LG Flatron L17NT-A no power

Very happy with the result! i was already planning to buy a led tv and use it as my monitor. It would cost me about $100 compared to this $2 fix.

The ferrite bead was alright, i think it's the heat that caused the residue on the board and it was originally black with orange paint on top.

[atanas18]

Re: LG Flatron L17NT-A no power

Hi all.

This is my first post here, but I'm very happy about the things I found in this thread.

I have LG Flatron L19175 which is dead. No indications on the panel, no leds flashing, no backlight, just nothing.

I do the measures described in this thread and think my power board is OK.

Here are some numbers:
Main voltage is 230V
C101 - 313 Vdc
U101 (FAN 7601) - between pin1 and pin5 - 295Vdc
Then I measure the 11 pin connector against PG2.
On pins 6 and 7 I get 4,91Vdc
On pins 10 and 11 I get 16,45Vdc

However, I start to measure the logic board. I get too low voltages there (on U801 - KIA 78D33F - next to the 11 pin connector).
The input against was showing 0.14Vdc and the output 0.01Vdc (0.01 could be an error into my tool).
So because I was just curious, I measure the 11 pins once again with both boards connected to each other.
I notice that the voltages at pins 6,7,10 and 11 was dropped and decreasing till I hold the probes on them.

I disconnect the boards and measure the power board once again. All the voltages are with the same values as the first time. Then I connect the boards again and measure. I notice, that the voltages was increased with +2Vdc, but dropping again.
So, in a minute to all these four pins I get 0.00Vdc.

I'm not sure what's going on, but there seems to be issue with one of the boards and I'm not really sure which one. The power board is working great when it's standalone, but connected to the logic board it's dropping the power. I'm not sure if this is power board issue or the logic board create the dropping power issue.

Any help is highly appreciated!

PS... I forgot to mention that one of the caps is already replaced from previous issue (black cap next to the green ones - 470/35 is the new one).