Re: Samsung 242mp PSU problem
At last an update:
I've isolated the IC306 (KIA7045RTF) from the RESETn line by removing R308 (0 Ohm jumper) ( schematic on page 67 of samsung_242mp_chassis_po24fs.pdf ).
Now with mains plugged in:
Output of IC306 is 0V all times. IC306 input (5V_STDBY) measured at +5V
I still measure +2,5V on the RESETn line.
When RESETn shorted to GND via DMM (Amp range), I measure 10mA to ground.
When RESETn shorted to +3,3V, the +3,3V drops to 2,95V.
But monitor won't switch...
pe9ghz
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Last Activity: 06-07-2012, 08:01 AM
Joined: 01-31-2012
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Re: Samsung 242mp PSU problem
IC304 is not mounted, but the surrounding components are present, incl R 220 Ohms Pullup to +3.3V. Thats why I thought that the +2,5V measured at the Reset line is suspect.
I'll try to remove the IC304 (or perhaps it will be easier to isolate it's output)....Leave a comment:
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Re: Samsung 242mp PSU problem
Thanks for your reply.
I've done some measurements.
With PSB connected to mainboard, not "jumpstarting" as an MCU output pin directly controls the PS ON/OFF line (verified connection is real, near zero ohms).
Referencing the schematics in the servicemanual (see earlier in this thread for link):
+5V_STDIN at Pin2 of CN601 (page73): +5,4V
+5V_STDIN at FT671 / C624: +5,1V
+5V_STDIN_SUB at FT673 / C660: +5,1V
+3.3V_LIVE at FT319: +3,28V
+5V_STDIN at R307 / input IC306 (KIA7045...Leave a comment:
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Re: Samsung 242mp PSU problem
Update: Replacement caps arrived today. Mounted them to the PSB.
Unfortunately no improvement at all:
When Jump-starting the PSB alone, all voltages are present (same as before).
When PSB connected to mainboard:
Same musquito noise as before . 5V stdby present, but Monitor won't switch on.
...
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Re: Samsung 242mp PSU problem
I've finally had some time and measured the (unloaded) output voltages of the PSB without connected to the mainboard, but jumpered the startup On/Off input with a 3k3 resistor to the 5V_STBY.
All output voltages are present, but I noticed the +12V was a little too low (11,8V).
All other voltages are correct.
I've just ordered replacement caps for every one that I hadn't replaced yet (mainly the secondary side smoothing caps).
It was not easy to find correct sized ones, especially the thin but high 3300uF/10V at dia=9,5mm, height=30mm,...Leave a comment:
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Re: Samsung 242mp PSU problem
With nothing connected to the PSU, I measure 5V to 5,4V at the 5V_STDBY output pin. All other outputs are 0, which is logical as the PSU is in standby-mode.
How could I "start up" the power supply in normal mode, but with nothing connected to the mainboard?
Could this be done by merely connecting 5V_STDBY to the "On/Off" pin ?
The high pitched "musquito" noise is not present when nothing is connected to the PSU(except mains AC off coarse).
@Selldoor, You are correct...Leave a comment:
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Re: Samsung 242mp PSU problem
I wish you hadn't told me selldoor ;-)
After having worked yesterday night (also several times switched off and on with short pauses), unfortunately it wouldn't turn on again today. Even after repeatedly "wiggling" the connector that did the trick before. No luck :-( Also wiggled the other connectors on the board but nothing seems to work.
The high pitched sound (like a musquito) is still coming from the PSU board, and 5V STDBY is nicely present.Leave a comment:
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Re: Samsung 242mp PSU problem
Good news, guys!
Today I spent a lot of time trying to draw schematics of the PSU and later on doing some measurements trying to find the fault.
At first I measured a fast varying 9-11V at the Vcc pin of the DM0365R, but still no voltage was present on the secondary side after the rectifier diode for the 5V STDBY.
Later on, to my surprise, the 5V STDBY was measured a nice 5V-5.4V (edit: at this time, the Vcc of the DM0365R was measured a steady 14,7V. A good sign).
Very strange... This was the first time I measured the...Last edited by pe9ghz; 02-05-2012, 04:36 PM.Leave a comment:
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Re: Samsung 242mp PSU problem
I finally could take some pictures of the PSU board today.
I didn't want to scale them down (and loose sharpness), so I host them on my website (I hope this is OK):
[URL="http://pe9ghz.org/cmsms/uploads/images/pcbs/samsungpsu/pe9ghzPSTOP.JPG"]pe9ghzPSTOP.JPG[/URL]
[URL="http://pe9ghz.org/cmsms/uploads/images/pcbs/samsungpsu/pe9ghzPSBTM1.JPG"]pe9ghzPSBTM1.JPG[/URL]
[URL="http://pe9ghz.org/cmsms/uploads/images/pcbs/samsungpsu/pe9ghzPSBTM2.JPG"]pe9ghzPSBTM2.JPG[/URL]
[URL="http://pe9ghz.org/cmsms/uploads/images/pcbs/samsungpsu/pe9ghzPSmodel.jpg"]pe9ghzPSmodel.jpg[/URL]...Leave a comment:
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Re: Samsung 242mp PSU problem
Thanks! that must be the right datasheet NCP1230...Leave a comment:
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Re: Samsung 242mp PSU problem
Your RP839 looks the same as on mine.. Black body power resistor. It has a (faint) marking: 8.4Ohm, maybe....Leave a comment:
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Re: Samsung 242mp PSU problem
Thanks,
IC804S (hard to read from the pictures) has a marking 230D6 (SOIC8).
Some others:
IC801S = ST L6561D SO-8 Power Factor Corrector [URL="http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001174.pdf"]PDF[/URL]
I'll study the application note and try to compare it with the actual PSU board.
IC802S = DM0365 (probably FSDM0365RN - Green Mode Fairchild Power Switch) DIP8.
This could be the regulator for the stdby_5V.Re: Samsung 242mp PSU...Leave a comment:
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Re: Samsung 242mp PSU problem
Hi,
this is my first post here..
I'm following this thread with high interest.
I too have a broken Samsung 242MP power supply (PN120LPS-VF).
The TV/Monitor won't switch on anymore, no stdby led, nothing....
My symptoms on the PSU are: No 12V main, no 5V main, no 24V, no 5V STDBY.
Voltage at BIG Cap: 380V (w/ 230V 50Hz mains).
I've replaced several smaller cap's (not all) with new, good quality Low ESR ones, but none of the original caps seemed really "bad" (all of them measured capacity's within...Last edited by pe9ghz; 01-31-2012, 05:22 PM.Leave a comment:
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