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Old 01-07-2022, 11:19 AM   #1
thetonywarren
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Default LG Flatron L1910S DEAD

I have a LG Flatron L1910S that is dead, no led's no backlight nothing.......I took off the back and took a look at the caps, all appear to be good, although I know that's not a true test......I took voltage readings at CW301, Without the main board connected, Im getting 5vdc and 14vdc, WITH the main board connected, Im getting 4.13vdc and 16vdc. Please see pictures for details, I think the attached diagram is correct for the SMPS. Any thoughts or suggestions where to look next....I can send better pictures and take measurements if needed.

Thanks in advance for any help.
Attached Images
File Type: jpg fan7601_lien_chang_ai-0066_l1720p_l1750s_inverter_lcd_sch.pdf_1.jpg (315.7 KB, 10 views)
File Type: jpg 2022-01-07_11-10-59.jpg (115.4 KB, 12 views)
File Type: jpg PXL_20220107_165530153.jpg (617.7 KB, 13 views)
File Type: jpg PXL_20220107_165537224.jpg (504.6 KB, 11 views)
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Old 01-07-2022, 12:56 PM   #2
R_J
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Default Re: LG Flatron L1910S DEAD

I would start by replacing C109 (c108 schem) and C107. See if this fixes the low +5v. It may also be that C205/C206 are weak

Last edited by R_J; 01-07-2022 at 01:11 PM..
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Old 01-07-2022, 01:45 PM   #3
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Default Re: LG Flatron L1910S DEAD

I changed out C205/C206 with new caps 1000uf/25v, but no change, I guess I'll need to source new caps for C109 and C107, as I dont have those values on hand......
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Old 01-07-2022, 03:34 PM   #4
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Default Re: LG Flatron L1910S DEAD

Is it possible to subsitute the 0.47uf cap @ C107 with another value? I found a cap to replace C109, but dont have one for C107, not sure if that's a possibility or not?????
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Old 01-07-2022, 03:51 PM   #5
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Default Re: LG Flatron L1910S DEAD

I have two caps, one of 2.2uf and another is 0.22uf, will either of those be ok???

both are rated at 50v
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Old 01-07-2022, 04:57 PM   #6
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Default Re: LG Flatron L1910S DEAD

I would suspect C108 first as it is for the vcc of the ic. You could check this voltage with the main connected, but be careful not to short the ic. and this is on the hot side of the power supply. Looks like this vcc should be about +12VDC

I would just bridge the 0.47f with the 0.22f and see if it help the 5 volts stay up, Just solder it across making sure the leads don't touch anything else.

Last edited by R_J; 01-07-2022 at 05:06 PM..
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Old 01-07-2022, 05:49 PM   #7
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Default Re: LG Flatron L1910S DEAD

Before I saw your reply, I soldered in the 2.2uf in place of the 0.47uf just to try it, and it came right on.....I'll get a new 0.47uf and put that in its place when it comes in......I'll update when I get the new 0.47uf cap.......
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Old 01-07-2022, 08:36 PM   #8
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Default Re: LG Flatron L1910S DEAD

Good to here, I would replace C109 (33f/50v?) as well, the circuit is on all the time and those small caps dry out over time.
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Old 01-07-2022, 09:07 PM   #9
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Default Re: LG Flatron L1910S DEAD

Yep, I appreciate the help, I actually replaced every cap on the SMPS, so the bad one was the only one I didn't have on hand.....go figure.......
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Old 01-13-2022, 08:51 AM   #10
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Default Re: LG Flatron L1910S DEAD

FYI, I replaced the 0.47uf cap and it's working now, I appreciate the help....

Here's a pic of the screen afer cap replacement....
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