Samsung 242mp PSU problem

[selldoor]

Re: Samsung 242mp PSU problem

Excellent! - switching off and back on will be the next test

I would say - yes - post away some schematic is better than none perhaps you can emphasize the board revision as there were some significant differences between yours and Jont3's.( have you any idea what else they did so as to reverse the polarity of that cap?) Post using the manage attachments so that they remain if you close down your host site. Perhaps you could also repost the pics of your board.

[pe9ghz]

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.

[selldoor]

Re: Samsung 242mp PSU problem

Bummer! Best to start again. - as I recall you didnt change all the small caps. With nothing connected what voltages are you getting at the connectors and is the noise still there when nothing is connected to the power board.

[Jont3]

Re: Samsung 242mp PSU problem

@pe9ghz check your mainboard.... My only advice.

I still have no clue of whats gooing on with my beast, resoldered some part of main without any luck, but i did discover that putting a small plastic washer under pcb upper right screw of main pcb (PSU at my right) did make the thing work, removing the washer and it does not work. So been using this for 3days with a little washer about 1,5 - 2mm thick, plugged in/out 30 times tapping a little here and there to stress the symptoms but no it still works. Not a permanent fix but this will have to work for a while as it eats to much time :P this screen is the worst heat developing screen i ever had for computer display so no wounder things go bad, a little portion of luck and the heat might fix this permanently to.

As all might point to PSU it probably is not, i checked my mainboard according to the service manual posted earlier, even with a scope. It all turns out fine pointing to faulty PSU, but that was not the case.

[pe9ghz]

Re: Samsung 242mp PSU problem

Bummer! Best to start again. - as I recall you didnt change all the small caps. With nothing connected what voltages are you getting at the connectors and is the noise still there when nothing is connected to the power board.

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 that I didn't change all small caps yet.
I've been reading some postings about psu problems of the Syncmaster 226BW, and they usually are fixed by replacing the (higher cap, low voltage) output caps.
I think I'm gonna try this next (once I have obtained replacements).

[retiredcaps]

Re: Samsung 242mp PSU problem

Could this be done by merely connecting 5V_STDBY to the "On/Off" pin ?

Yes, you can jump it. PlainBill and tom66 have described this method many times as per

https://www.badcaps.net/forum/showpo...1&postcount=45

Alternatively, you can try connecting 2 AA batteries in series or find one CR2032 3V battery.

[pe9ghz]

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, pitch=5mm in Low ESR type. Most are a little bit taller.

I also ordered some replacement SMD Caps for the mainboard, as some of the metal-can 100uF/35V SMD elco's look a little bit bulged on the top (but not much). It might be a sign of a bad cap.

I'll keep you posted.
Ed

[mzr910]

Re: Samsung 242mp PSU problem

i have too half-dead 242mp PSU

my symptoms are - 5v standby - ok , 5 v main ok
12v - 0v , 13v - 3v and fall , 24v - 13v and fall , if unloaded - same resultats and hearing some high pitched noise constantly at all

[pe9ghz]

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.

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, pitch=5mm in Low ESR type. Most are a little bit taller.

I also ordered some replacement SMD Caps for the mainboard, as some of the metal-can 100uF/35V SMD elco's look a little bit bulged on the top (but not much). It might be a sign of a bad cap.

I'll keep you posted.
Ed

[jetadm123]

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.

I may have missed something, but you're using the 5V standby to basically "jumpstart" the power supply. The p/s "on" signal to turn on the power supply should be coming from the main board. Since you're not getting the 3.3V "on" signal when you push the on/off button on the front panel, make sure 5V is reaching the main board. Check for any blown fuses and voltage regulator outputs on the main board.

[pe9ghz]

Re: Samsung 242mp PSU problem

I may have missed something, but you're using the 5V standby to basically "jumpstart" the power supply. The p/s "on" signal to turn on the power supply should be coming from the main board. Since you're not getting the 3.3V "on" signal when you push the on/off button on the front panel, make sure 5V is reaching the main board. Check for any blown fuses and voltage regulator outputs on the main board.

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 Reset circuit) (page67): +5,07V
Output at pin3 of IC306 / R308 (RESETn signal) and JIG_RESET pin at CN301: +2,5V ->> shouldn't this be near 3,3V ??
Could IC306 (KIA7045) be bad ??
POWER_ON signal from MCU to PSB: 0V

MCU IC300 feels a little bit warm (getting +3.3V VCC supply), but it's not responding to any frontbuttons or remote. (Seeing voltages vary on some pins of CN3000 when pushing buttons / remote).

thanks for any feedback
Ed

[jetadm123]

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 Reset circuit) (page67): +5,07V
Output at pin3 of IC306 / R308 (RESETn signal) and JIG_RESET pin at CN301: +2,5V ->> shouldn't this be near 3,3V ??
Could IC306 (KIA7045) be bad ??
POWER_ON signal from MCU to PSB: 0V

MCU IC300 feels a little bit warm (getting +3.3V VCC supply), but it's not responding to any frontbuttons or remote. (Seeing voltages vary on some pins of CN3000 when pushing buttons / remote).

thanks for any feedback
Ed

Looking at the schematic:

1) Are they also using IC304 on your board? That would mean two voltage detectors, KIA7029 and KIA7045, are being used as part of the reset circuit.

2) I tried looking the parameters for the reset pin for the GM1601 scaler chip, but no luck.

The question at this point: is the 2.5V input to the the reset pin of the GM1601 holding that chip in a reset mode and preventing it from outputting the PS_ON signal?

My thought at this point: what if you removed IC304 and IC306 from the board? Would the reset pin on the GM1601 interpret that as a 0V input and allow it to start?

[pe9ghz]

Re: Samsung 242mp PSU problem

Looking at the schematic:

1) Are they also using IC304 on your board? That would mean two voltage detectors, KIA7029 and KIA7045, are being used as part of the reset circuit.

2) I tried looking the parameters for the reset pin for the GM1601 scaler chip, but no luck.

The question at this point: is the 2.5V input to the the reset pin of the GM1601 holding that chip in a reset mode and preventing it from outputting the PS_ON signal?

My thought at this point: what if you removed IC304 and IC306 from the board? Would the reset pin on the GM1601 interpret that as a 0V input and allow it to start?

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).

[Vlada3600]

Re: Samsung 242mp PSU problem

Hi,l am the first time visit this forum.
And a have the same problems you discus,and the SAME time it began!
Have your monitors comeback to life now?

[pe9ghz]

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).

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 on in any of the above situations.

[selldoor]

Re: Samsung 242mp PSU problem

Looks very but how about posting pictures of your main board


Did you check out IC803s - seemed to be problematic in other cases I linked to one
near the beginning of the thread and Plainbill gave some pins to test?

https://www.badcaps.net/forum/showth...997#post213997

[mzr910]

Re: Samsung 242mp PSU problem

some parts of BN96-01849A look like BN96-01850E

http://www.scribd.com/doc/56826695/I...ng-BN96-01850E

[Andreas84]

Re: Samsung 242mp PSU problem

I have the same problem with a samsung 242mp. Did you find a solution for fixing the problem. Which parts have you replaced?

Could you give me some tips for repairing this monitor with the mentioned problems?

Thank you for your help.

Merry christmas to everyone.

Best regards,
Andreas

[selldoor]

Re: Samsung 242mp PSU problem

It is almost 12 months since the last post - who is your query directed at.
I am not going to read through 58 posts to guess what your problem might be.

This set can have at least 2 different boards so it would probably be better if you started again.

Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back (in the same orientation) and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed

https://www.badcaps.net/forum/attach...7&d=1280167246

https://www.badcaps.net/forum/attach...6&d=1280167246

https://www.badcaps.net/forum/attach...4&d=1280167246

It will be useful if you can say what the supposed fault was and a bit about yourself - skills tools etc.

[laptop engineer]

Re: Samsung 242mp PSU problem

please any one can tell me what is this Ic (with the red color square) number ?