LG Flatron L17NT-A no power

[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

(2) 1000μf, 25v, P10278-ND EEU-FC1E102 @ $.87 ea
(2) 1000μf, 16v, P12366-ND EEU-FM1C102 @ $.59 ea
(1) 680μf, 25v, P12390-ND EEU-FM1E681 @ $.59
(1) 470μf, 25v, P12388-ND EEU-FM1E471 @ $.50
c103: 33μf, 50v, P10320-ND EEUFC1H330 @ $.27
c105: 0.47μf, 50v, 493-1885-ND UPW1HR47MDD @ $.34

The number that ends in ND is the Digikey stock number, the second number is the manufacturer's part number if you prefer to buy from another source. The dimensions don't exactly match, but none are higher (I think, double check when you order).

PlainBill

[stj]

Re: LG Flatron L17NT-A no power

.47uf 50v

i never understand why stuff that small isnt done with polyester!

[PlainBill]

Re: LG Flatron L17NT-A no power

.47uf 50v

i never understand why stuff that small isnt done with polyester!

I don't know. Cost, reliability, availability, characteristics, size, tradition?

Maybe someone had a bad experience once, like I did. Back in the 1980's the company I worked for used .1 uF 50 V ceramic caps in an axial package for power supply decoupling. There was one near every IC, the typical board had a couple of dozen ICs on it. Some boards had over 100 ICs. Purchasing liked to buy a years supply at a time. The components on bulk reels were feed into a sequencer which combined them into a sequenced reel for the automatic insertion machines. The net result was that a new lot of components could be in the production stream for a month or more before they ever hit the test area. (I was the lead tech in the production test area).

Somehow a bad lot slipped through the manufacturer's test process, and our incoming inspection process. About 1 in 20 of these $@!%@#%@# parts would short at voltages as low as 5Vdc. The only safe way to identify the bad part was to hook up a 5 volt current limited power supply to the board and measure voltage drop along the power traces until you found a spot where the voltage stabilized. Then you start cutting cap leads until the voltage rose. It wasn't unusual for the voltage to jump as you cut one cap, then drop again as another one shorted.

PlainBill

[Elmojo]

Re: LG Flatron L17NT-A no power

PlainBill, thanks so much for the part numbers. I'm not sure why I couldn't find those myself. You mention that the dimensions are not exact, so I assume they don't have to be, other than fitting in the case, right?
What about the pin pitch? I didn't think about that until later. Are these all pretty standard or do I need to sorry about them not fitting?
As for the actual replacement, is this just a simple through-hole desolder/resolder job or is there something special I need to know?
Thanks again for all your help,
Elmojo

[Elmojo]

Re: LG Flatron L17NT-A no power

Also, I notice that the 1000x25V caps are 12.5mm wide vs 10mm wide for the stock ones.
These are already pretty close together, do you think I'll have trouble making them fit?
Is it a problem if they touch?

[PlainBill]

Re: LG Flatron L17NT-A no power

Also, I notice that the 1000x25V caps are 12.5mm wide vs 10mm wide for the stock ones.
These are already pretty close together, do you think I'll have trouble making them fit?
Is it a problem if they touch?

Dimensions are non-critical, except for clearance. You will have to determine actual spacing, I felt from the pictures is should not be an issue. Both 10 and 12.5 mm caps usually have the same pin pitch.

Replacing the caps is usually quite straight forward. I believe this is a single sided PC board, so there are few problems. Just make sure you check orientation before soldering in the replacements.

I usually make a crude sketch showing where each cap goes, pull all the old caps and cleaning out the holes with a dissecting pick as I go. Then I insert all the replacements, then double check the orientation. Solder, trim the leads, scrub the board with alcohol, then check for solder shorts.

PlainBill

[Elmojo]

Re: LG Flatron L17NT-A no power

Cool, sounds pretty straightforward.
I got the caps ordered, so hopefully I'll get them next week.
Any idea where digikey ships from? Just curious about shipping time.
Yeah, it's a pretty simple board. The underside spacing is plenty wide, so even I should be able to handle it.
I'll post a few pics as the replacement progresses.
If I replace all these caps and still have no power, what's the next step?
Or are we fairly sure the caps are the sole issue?

Elmojo

[PlainBill]

Re: LG Flatron L17NT-A no power

Cool, sounds pretty straightforward.
I got the caps ordered, so hopefully I'll get them next week.
Any idea where digikey ships from? Just curious about shipping time.
Yeah, it's a pretty simple board. The underside spacing is plenty wide, so even I should be able to handle it.
I'll post a few pics as the replacement progresses.
If I replace all these caps and still have no power, what's the next step?
Or are we fairly sure the caps are the sole issue?

Elmojo

Digikey ships frm Thief River Falls, MN. Google it.

The behavior of the power supply is consistent with a bad Vcc cap for the SMPS controller. That is no guarantee, but that's the way to bet.

If it still doesn't work we troubleshoot for power supply problems.

PlainBill

[Elmojo]

Re: LG Flatron L17NT-A no power

Alright guys, we're making progress!
I got the caps from Digikey yesterday.
Tonight, I replaced all the caps, powered up the board, and measured the voltages on the 12-pin plug again.
This time, I got 2-5v sources and 2 13.xxV
Yay!
Why is my text right to left suddenly?

[PlainBill]

Re: LG Flatron L17NT-A no power

Alright guys, we're making progress!
I got the caps from Digikey yesterday.
Tonight, I replaced all the caps, powered up the board, and measured the voltages on the 12-pin plug again.
This time, I got 2-5v sources and 2 13.xxV
Yay!
Why is my text right to left suddenly?

You are receiving the wisdom of Solomon?

PlainBill

[Elmojo]

Re: LG Flatron L17NT-A no power

EEETS ALIIIIVE!!!!
I absolutely cannot believe it, but this thing is working 100%!
Bill, you should change your name from PlainBill to PlainAwesome!
I changed out the caps, reassembled everything, and it fired up first time.
I don't even see any dead pixels on this sucker.
I can't thank you enough for the time and effort you spent helping me through this repair.
Is there any way to award you stars or points or whatever on this site?
I only hope I can one day help someone else in the same way.

Thanks again!
Mike P.

[PlainBill]

Re: LG Flatron L17NT-A no power

EEETS ALIIIIVE!!!!
I absolutely cannot believe it, but this thing is working 100%!
Bill, you should change your name from PlainBill to PlainAwesome!
I changed out the caps, reassembled everything, and it fired up first time.
I don't even see any dead pixels on this sucker.
I can't thank you enough for the time and effort you spent helping me through this repair.
Is there any way to award you stars or points or whatever on this site?
I only hope I can one day help someone else in the same way.

Thanks again!
Mike P.

Congratulations. There are two ways to repay me. The first is difficult - help others with their monitor problems. I note that is already one of your goals.

The second is easier. My avatar is a picture of my wife. This was taken last month. In the background is Diamond Head. You can send us back. Two weeks would be nice. Two months would be even greater.

PlainBill

[Elmojo]

Re: LG Flatron L17NT-A no power

Yeah, I bet it would! My friend and his wife just came back from HI about a month ago and said that they liked it so much, they were job hunting before they came home!
I've never been myself, but I hear it's beyond words.
I guess I'll just have to try the "hard" method of repayment.
Thanks again for all your help,
Mike P.

[Kilohertz]

Re: LG Flatron L17NT-A no power

Hi guys,

First Post here. Just wanted to say THANKS!!!

You just saved me a ton of money and time troubleshooting my Flatron 1952. My PWM cct is identical to the one posted here (electrically) and I changed out all the caps and Shazamm! She's alive again.

Funny thing, in my research I studied the Fairchild ap note and found that LG (Lein Chang inverter) uses almost the identical cct as the ap note, including ref. designators. Too funny. Saves on engineering costs I guess.

Thanks again.

Cheers

Paul

[fsearcy2]

Re: LG Flatron L17NT-A no power

Plainbill i was wondering if you might help me out on my lg monitor it is the same exact setup you were helping Elmojoe i followed all of the steps and i have a working power supply but the monitor is still dead i did see once when i tried to hit the power button the leds flashed quickly once and thats it. thanks in advance

[PlainBill]

Re: LG Flatron L17NT-A no power

Plainbill i was wondering if you might help me out on my lg monitor it is the same exact setup you were helping Elmojoe i followed all of the steps and i have a working power supply but the monitor is still dead i did see once when i tried to hit the power button the leds flashed quickly once and thats it. thanks in advance

Glad to help, it might take a couple of posts to get me up to speed. You say you have a working power supply. Just to give me a sense of security, how did you establish this?

With a good power supply, the two places to look are the logic card, and the panel itself. Would you post pictures of the logic card, please.

PlainBill

[fsearcy2]

Re: LG Flatron L17NT-A no power

Thanks Plainbill i found this thread then since it was the same exact board i followed the directions you gave in the post to Elmojoe and i have power at the points you pointed out so i didn't see anything else because that fixed his problem but not mine so i need some education. so here is a couple of pic's to get us started.

[PlainBill]

Re: LG Flatron L17NT-A no power

Thanks Plainbill i found this thread then since it was the same exact board i followed the directions you gave in the post to Elmojoe and i have power at the points you pointed out so i didn't see anything else because that fixed his problem but not mine so i need some education. so here is a couple of pic's to get us started.

Well, one thing stands out. I don't see a cable connecting the power supply to the logic card.

PlainBill

[fsearcy2]

Re: LG Flatron L17NT-A no power

yeah i pulled the cards out and disconnected the cables but that was after i did all of my testing to see if the power supply was working i wanted to check the boards out really well to see if i could notice anything that didnt look right.

[PlainBill]

Re: LG Flatron L17NT-A no power

yeah i pulled the cards out and disconnected the cables but that was after i did all of my testing to see if the power supply was working i wanted to check the boards out really well to see if i could notice anything that didnt look right.

A few points. I'm old and crotchety. Communication is important. Long sentences without punctuation confuse me. I compensate by moving on to the next thread.

First, I'd like a definitive answer to an earlier question. How did you determine the power supply is working? Answers like 'and i have power at the points you pointed out so i didn't see anything else' don't really do much except give me a headache. Answers like "I measured 5.43 volts at pins 4 and 5 of the 18 pin connector on the logic card" tend to indicate someone knows what he is doing.

Next, I have labeled three ICs on the logic card. What are the part numbers of these ICs, and what are the voltages on the pins of each? I suggest using the screw head next to the Ic labeled B as the ground point.

For extra bonus points, post links to datasheets for them.

PlainBill