Re: Samsung SyncMaster T24B350
Yes, in this video he replaced the LDO with 3.3v (sot-23) on a board with a regulator.
Yes, in this video he replaced the LDO with 3.3v (sot-23) on a board with a regulator.
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Re: Samsung SyncMaster T24B350
Ok.. Quick Update. All videos, though not in english, implied the little transistor gets +5.2 V from the board and generates the Mem_VCC. However, upon running continuity check the MEM_VCC comes from Standby Voltage from the PS board!!!! I was not providing that, I was simply providing +5V, +11.9V, and GND.
Now with +5, STB(+5) and 11.9V with GND, the little transistor is getting 5V, but still the bottom right (Mem_VCC) is only coming to +.9 V. I don't know how that 3.3 is supposed to be generated. Looks like one trace goes to CPU, and others go to resistors (voltage dividers? - 22k and 10k = ~3.4 V Checks out)Last edited by jason123; 10-24-2023, 02:11 PM.Comment
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Re: Samsung SyncMaster T24B350
It's something like this (with a fixed output voltage of 3.3v).Attached FilesLast edited by lotas; 10-24-2023, 02:17 PM.Comment
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Re: Samsung SyncMaster T24B350
You can use:
S-1206B33-MT1G,
TS9011SCX,
MCP1700T3302E...
Yes, and you can solder some kind of 1117 33 to check on short wires.Last edited by lotas; 10-24-2023, 02:28 PM.Comment
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Re: Samsung SyncMaster T24B350
Thank you.. On orderComment
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Re: Samsung SyncMaster T24B350
Prepping the board - removed the regulator, and it looks like the 3.3 pin was barely hanging in there. But I measured the impedance between GND and 3.3 V node, and it's only ~30 Ohm.. is that right? I guess 3.3/30 is about 110 mA, but it seems very low.Comment
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Re: Samsung SyncMaster T24B350
Usually, like in such Samsung boards, because of this capacitor that you changed in the power supply, the motherboard also suffers, namely this regulator for 3.3v and micom Weltrend wt61p805, but I don’t see it on your board, maybe it’s located on another sides.
I just found a photo of your board, there’s nothing on the back side, you need to supply somewhere 2v from the laboratory power supply to this 3.3v point and observe what can heat up by increasing the current on the power supply and find the culprit who drains this power, this can maybe a ceramic capacitor, spi flash, eeprom,...Last edited by lotas; 10-24-2023, 06:33 PM.Comment
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Re: Samsung SyncMaster T24B350
I did comnect the on-board 3.3v to this node while regulator still on. No damage or overheatingComment
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Re: Samsung SyncMaster T24B350
But 30 Ohm is a low resistance for such a regulator, which drains the power supply.Comment
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Re: Samsung SyncMaster T24B350
Not sure if we can assume with power (3.3 V present) that 30 Ohm will result in 110 mA usage and that's 0.363 W for standby usage? (in addition to PS standby current?)
Anyway, LDOs are on order. and I don't know where the leakage is to get the 30 ohm. I see quite few ceramic caps, and one can be semi shorted, but not sure how to detect as ESR doesn't seem to catch them all.Comment
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Re: Samsung SyncMaster T24B350
But only when applying an external power supply and increasing the current, try to carefully lift the legs of the spi flash (1,2) and eeprom (8) to eliminate them.Comment
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Re: Samsung SyncMaster T24B350
Final Update: Ok, got the regulator, put it onboard, and voila, 3.3 is present. However, board still not turning on, and SOT23 is warmer than I'd like to see. Lifted the pins as in #35, no luck, still 31.5 Ohm across 3.3 and GND. Removed all caps on the line that I could see. Still 31.5 Ohm. Removed both memory chips on board - still no change.. at this point, board is throw away, so I removed the Big BGA / Processor and there it is. Must have had shorted pins or internal chip issue ... impedance now is 684 kOhm across the LDO (3.3 and GND) and the board is a designated as donor board
That's a wrap up.. thanks for the help.Last edited by jason123; 11-01-2023, 11:27 AM.Comment
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Hi guys, I’m back here my friend give me her tv, that doesn’t turn on and no standby red led. When u plug in the cord the red led of one two second is on, then turn off. If you push the power button or the remote the red led blinks but nothing happen. I give u some photo with voltage, don’t look the fuse….because I blow it for mistake nd I dint have the right replace so I just put it for test the tv. The standby voltage should be 11,88 volt on the diode, but I have 13 volts. I put in the photo the different volts I test and there are someone negative…I don’t know if it s normal. On... -
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