Re: Samsung 2493hm flashing backlight
Hello again,
Thank for the posts to McEugene and budm, sorry I didn't notice them, I didn't get a mail notification and I had lost hope about help on the forum. Good news is that I managed to repair another LG screen.... but that was easy, bulging cap, 0.30euro to repair.....felt really nice.
As I mentioned my screen now turns on and after few seconds it starts flickering. Since I am revisiting the problem and I refuse to throw the screen I will scan for and remove any tiny amounts of this horrendous brown glue and remove...
radicalmjp
Member
Last Activity: 02-14-2021, 06:54 AM
Joined: 10-01-2012
Location: Attica
-
Re: Samsung 2493hm flashing backlight
Forgot to mention!!
Yes, when the screen goes blank I can see the desktop with a flashlight.Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Transformer measurements
-------------------------
Old inverter board (fully disconnected from power and ccfl's)
transformer #1, S1+S2: 1712 ohm
transformer #1, S3+S4: 1700 ohm
transformer #2, S1+S2: 1754 ohm
transformer #2, S3+S4: 1719 ohm
transformer #3, S1+S2: 1747 ohm
transformer #3, S3+S4: 1694 ohm
New inverter board (fully disconnected from power and ccfl's)
transformer #1, S1+S2: 1662 ohm
transformer #1, S3+S4: 1654 ohm
...Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Ok guys I will do the measurements....just give me some time....going through some difficulties in life.Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Update!
I ordered a used inverter (yes I cheated) from ebay and installed it today. The screen works, turns on but if no input is connected it scans for inputs (digital/analog/hdmi) and after few seconds it starts flashing, until it is completely black. If there is a video signal from a PC then it turns on for less than two seconds and goes black, so I guess unless anyone suggests something I will study the "two seconds to black" thread.
Note: if the screen has been resting for some time it takes longer to go blank....Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Ok , removed most of the glue and where I didn't yet I at least cut and separated it from most components(will remove it all), this damn thing is like a chewing gum stuck under a cheap cafeteria table for 10 years... the purpose of this yuck eludes me as it seems randomly dropped on the board....why does a simple resistor need to be secured with glue, or a single capacitor but not the rest of the resistors?
Did the test with the two 12v lightbulbs from my motorcycle turn signals
With the inverter disconnected the lights...Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Ok, I dont have at hand car lights, so I guess I will go buy some cheap ones for my bikes turn signals.
I did try two 12v 10W ikea lights and they light up nice and bright with no flicker at all when connected to the 24v output to the inverter (inverter disconnected)Leave a comment:
-
Re: Samsung 2493hm flashing backlight
I have not abandoned this task....I am just swamped for now.... will get back to it with car lights to test... (anything else I could use to test except cart lights?)Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Ok, I think I might find some old working 12V car lamps somewhere.....will try tomorrow hopefully.
This is to check the 24V output to the inverter, right?Leave a comment:
-
Re: Samsung 2493hm flashing backlight
The two resistors measure (with the meter setting at 200k) 98.1 (left) and 100 (right)
The colours (not clear from this angle in the picture) are Brown-Black-Yellow-Gold which I found out that it amounts to 9.5 and 10.5 Ohms, so I guess that is correct.
Yes I must figure a way to remove the glue without causing more damage.
As I said earlier I am not very good at soldering/unsoldering and neither is my equipment, so I would really like to avoid replacing the caps, if you guys here think that the caps I used...Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Sorry for any confusion.
I mean the 24v_DET pin on the logic board as it appears in the top of the image in post #11
I have not done any measurements on the power supply output towards the inverter.Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Measured again the 24v pin with the inverter disconnected...exactly same voltages 4.7v with the screen on and 0.15v when off.....BUT I think it might be important to note that I hear the same intermittent audible sound as before from the power supply and the inverter disconnected, AND I managed to narrow the sound to the side of the board where the 240v (mains?) is connected.
So it seems the inverter is ok?Leave a comment:
-
Re: Samsung 2493hm flashing backlight
BL_EN measures 0V when off and a nice and steady 4.5V when on. I couldn't have a video signal from a PC because it's not very easy but if it helps with the measurements I will move a PC where the dissected screen is located.Leave a comment:
-
Re: Samsung 2493hm flashing backlight
The 24V pin when on measures 4.7V and when off 0.15V
The 82mf 450V capacitor when screen is off measures from 230-240 up to 320V, when on in gives 400V
Anyone thinks the inverter might be at fault or the power supply?Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Forgot to mention!!!
No change in voltage reading with screen off or on, at least on the pins I measured.Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Ok I did few measurements on the Logic Board
The +5V measure 5.3V, the 18V measure only 0.4V and I didn't try the 24V because I am not sure if I can use the same GND pin from the group with the many pins and would rather make sure with someone on the forum I can do so instead of toasting one of the few things that might still work on the screen....Leave a comment:
-
Re: Samsung 2493hm flashing backlight
I managed not fry myself or the screen!!
So the IC has this written on A6159-SK703-351K and I am pretty sure its a "STR-A6159 - LOW POWER OFF-LINE SMPS PRIMARY SWITCHER " which I assume is responsible for the high Hz AC for the flyback (hey I am learning stuff!!)
Here is the list of voltages with the screen on.
1-3: 0.6V
2-3: 16.30V
8-1: My volt meter on the 750V AC setting can't read it, it shows crazy numbers ranging from 100-200-10-199- etc. (I guess frequency is too high for my cheap...Leave a comment:
-
Re: Samsung 2493hm flashing backlight
Ok will do so on Monday, if I am not mistaken I just test all pins with GND and check if the values are withing specs, and of course I will report here....Leave a comment:
-
Re: Samsung 2493hm flashing backlight
@Rtech: so if I try with to measure with the inverter disconnected and I get the same number it means that the power supply is at fault? If it's a short how can I tell where it is?
@the resistors look bad but measure ok, they were covered with glue that was burnt to black (so I removed it) the diode seems to work but I can check if needed. I can post better pictures soon if needed.Leave a comment:
-
Re: Samsung 2493hm flashing backlight
All caps have been changed. From another post on this forum I think the starter cap is in the first image (P1) down center, the left of the two small light blue caps. It is also the worst soldering on the board which is why I don't think I should tinker with it much more (I started soldering by using an underpowered soldering iron, now I use a stronger one)
It looks (and is) bad but continuity checks out. Voltage on it when on is 0.5V?
Sorry for crappy images, will make better ones if needed when I find the camera....Leave a comment:
No activity results to display
Leave a comment: