Samsung P2570 Monitor Component Identification - Page 1
Forum section: electronics / repair

author: Divvi
author_rank: Contributor
timestamp: June 23, 2015, 10:20:35 pm
content: Hello All,I recently acquired a samsung monitor that was being scrapped at work due to a malfunction. Upon opening, I noticed a discoloration on the backside of the main board. I'm having a hard time identifying the component which I suspect is the culprit:I believe the markings are:17-181007BGCan anyone point me in the right direction?Thanks

author: Yansi
author_rank: Super Contributor
timestamp: June 23, 2015, 10:29:39 pm
content: It's an AMS1117-1.8 voltage regulator.Very nicely cooked, indeed. Interesting how they've used the two diodes to shunt the excessive voltage. Also improperly done decoupling. Wow... what a junk.

author: Divvi
author_rank: Contributor
timestamp: June 23, 2015, 11:12:43 pm
content: Quote from: Yansi on June 23, 2015, 10:29:39 pmAwesome, thanks for the help. Guess I should check the diodes in addition to replacing the reg.

author: wraper
author_rank: Unknown
timestamp: June 23, 2015, 11:23:29 pm
content: Quote from: Yansi on June 23, 2015, 10:29:39 pmWhat so improper? I see ceramic cap with a resistor in series on the output.

author: Rasz
author_rank: Super Contributor
timestamp: June 23, 2015, 11:32:39 pm
content: oh wow it went full violet

author: Yansi
author_rank: Super Contributor
timestamp: June 23, 2015, 11:41:04 pm
content: There is no cap on the input. That one in between the two diodes is just.. eh... not right where I'd rather see it.The circuit seems to be designed to fail. The 1117 regulator can accept 16 volts maximum. There is quite probably about 17volt input, shunted with the two diodes to get just about the 16 volts needed.If I remember it right 17V is a common voltage in LCD monitors for powering the CFL inverters - please correct me if I am wrong! I'm not sure now, I think I've seen the 17 volt voltage in some monitors... If it's not true, please forgive, I usually avoid monitor repairs, this stuff is too much boring for me do I don't know much about :-)The second possibility is that it might be just at about 5V input voltage or so and they've used the diodes to decrease the heat dissipation on the regulator. Neither this is an excuse, because still it overheated and finaly blew. Still it was designed wrong or purposely to be likely failing a day or two after the warranty expires.By the way, I'd be concerned about the circuitry connected after this blown vrg. It might be blown too, bcs of the failed regulator.Rasz: Yea

author: wraper
author_rank: Unknown
timestamp: June 23, 2015, 11:45:54 pm
content: I don't think there is high voltage on the input. There are plenty of DC/DC converters on the board.

author: Yansi
author_rank: Super Contributor
timestamp: June 23, 2015, 11:50:22 pm
content: I wouldn't be so sure about that, unless you have the schematic or a proof. But it won't change anything though: The design was either bad, or purposely done to fail. Thumbs down for samsung.

author: wraper
author_rank: Unknown
timestamp: June 24, 2015, 09:22:51 am
content: Quote from: Yansi on June 23, 2015, 11:50:22 pmThe same goes for you too about making claims. BTWAMS1117 datasheet don't have any requirements for input capacitor to call this "improperly done decoupling" right away. Also this isn't particularlyAMS1117-1.8 but something else xx1117-1.8

author: amyk
author_rank: Super Contributor
timestamp: June 24, 2015, 11:35:04 am
content: This isn't AMS - that's not their logo.It's anAP1117.