Black LG L1952T-Sf Sceeen Test

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Nah, use plastic strips, I use that insulation plastic found in power supplies under the PCBs. Cut up into some 1.5cm x 8cm lengths, force a corner into the joint, bend the plastic over and get the other end in, the add a couple or more strips until you can pop a case latch.

Repeat around edge. Take your time, it's much quicker after the first couple monitors :)

Trying different places to start might help, once you feel where the latch tabs are, it's easier.

Grant.

After searching the Lge sites and not seeing this monitor listed in discontinued (suspect very old), i decided to just disassemble it anyway. Removed the four screws, then levered the screen surround off breaking every plastic latch, four per side.

Then the innards would come out. Sheesh, all held together by tape, except for the clip on cover for the screen power cables, which obviously provided a shield path for the screen itself back to the cage containing the power supply and driver boards.

No burnt out track or obviously damaged components on either board, so I'm wondering if I could play with bits a bit more?

Q. what voltages would the power supply being supplying directly to the screen? Just labelled high voltage on the sockets.

I assume these drive the backlit lamps?

Found a pdf that says 5V, 0.745ma normal, 3A max inrush? Does this sound correct? There was nothing specific about lamp supply power .

Q. How do a I drive the DIM & M/S pins? There is an 11 wire jumper from PS to I/O board, pins labelled as follow; # PS(IO)

1. 12V
2. 12V
3. GND
4. GND
5. 5V
6. 5V
7. GND
8. NC

Thank you, very helpful. will keep it in mind for next time.

Can happen first time. You DO get better at it after a few.

You want permission? Goferit. But play safe.

Yup. The other board (video) provides the signal info to the screen.

Pass.

Bet the manual IS out there, but I don't have the energy right now to chase it. It's not essential. Start with some basic fault-finding which doesn't need a manual, but does need some care.

Before testing though, have a close look all over the boards - both sides. (A good Mk1 eyeball can preempt a LOT of measuring and circuit examination.) You are looking for:

. bulging/leaking electros on the PSU board. . any signs of charring or excessive heatingon the non-copper side of the PSU board. . any semis with damaged flat surfaces.

If nothing found, ...

With everything plugged together and AC applied, turn on with front panel switch (assuming there is one). Check for voltage ~340DC on the large cap on the PSU board.

If it is there, the fuse and rectifier bridge are working. Next, meter the labelled 5V and 12V points vs chassis ground. If OK, the switcher is running OK.

"Normally" the PSU board drives the backlighting in response to two control lines from the video board - an analog brightness line ("DIM") and an on/off function ("BL_EN") which is *generally* a 0/5V logic signal. If the above tests return OK, I often release the BL_EN out of the connector and force it to verify that the backlight system functions properly. The BL protection circuitry (on the PSU board) is not disabled by this step, but I don't persist for more than a couple of secs on this.

Hope this isn't a case of teaching my grandmother how to suck eggs.

Nope, these are all new to me. Very helpful info there. thanks

I've fiddled with monitors in the past, basic fixing, but mostly it was case of just keeping the best, plus looked closely at laptop bits (no doco).

The fact that these are basically three modular bits, (LCD, PS & IO/ driver) encourages me to fiddle more.

Did a few Samsung ones recently - it was faulty electrolytics in all cases. Another had the added bonus of a blown fuse in the 18V line to the HT (lamp) EHT supply section.

Don't know why it blew, but when replaced with the correct value has worked without a problem for the last month.

My experiences with LCD monitor repairs have been similarly routine with the exception of Samsungs. I have several here where the micro (NT68F63L) appears to have decided that good signals are nonexistent.

Fixed a Samsung 943BW LCD Monitor this morning.

I'm not put off by opening the case, although on most LCD's to date it IS the most time-consuming part of repairing them.

Done lots, it's just these f#$@#$ Samsungs with the intractable micro issue that are bugging me right now. And (of course) the data sheet for the micro is nonexistent, so I can't even check the sense behind the widely-mooted "stick a 50R across pins 5 & 6" kluge.

as

Sounds Identical to the problem we have been having. We have over 30 of these 17 & 19", and 5 failed within 2 months.

One other we opened, had a newer model power supply in it, caps looked the same as the bad ones but were ok. Replaced them anyway.

Compared to the cost of replacing 30 monitors, this fix is a bargain.

Watch out for that fuse too (looks like a resistor) that takes the 13v to the screen inverter circuit.

On Sat, 24 Apr 2010 03:12:20 +0000 (UTC), terryc put finger to keyboard and composed:

Google suggests that the chassis number is LM57B.

Here is a service manual for MODEL: L1953H (L1953H-BFQ.A**MQP), chassis LM57B:

Here is a user manual for L1752T L1952T L1752TX L1952TX L1752TQ L1952TQ L1752TR L1952TR:

See pages 30 & 31 of the service manual.

- Franc Zabkar

Thank you for all those. most helpful. I have enormous trouble finding anything seful like that in service manuals online. Too many shonk sites.

On Mon, 26 Apr 2010 14:46:29 +0000 (UTC), terryc put finger to keyboard and composed:

Try filtering your Google hits:

- Franc Zabkar