How to solder this DC-jack? - Page 1
Forum section: electronics / repair

author: Charkel
author_rank: Contributor
timestamp: January 12, 2018, 03:33:12 pm
content: Hello!I am new to soldering but have a pretty nice station so I wanna learn. Apparently I bought the wrong DC connector. But it is the correct size so it should work. I was thinking instead of replacing the jack I just solder on the new one with wires and hang it out of the back.But it looks like the original jack has 4 pins. The one I bought only have 3??It's a Samsung 23A700D is it possible to find the documentation for the board?How can I do this? Here are some pictures. (sorry for the flux after my failed desoldering attempt)

author: Twoflower
author_rank: Frequent Contributor
timestamp: January 12, 2018, 05:13:39 pm
content: It is not easy so see through the flux but it looks like two or three of the pads, the upper most and the lower most are connected to the ground-plane. Probably also the right one (related to the last picture). But you should double-check this as it is hard to see: Some of the connector pins are connected to the big GND plane via four small traces. These pins are electrically connected to the same terminal on the cable.The one you bought has one connector that opens if you plug in the plug. Use a multimeter which ones show the expected voltage if you plug in the cable.About the polarity you should double-check were the connectors of the old ones are routed and compare that with the new one. Also make sure to strain-relieve and insulate the cable.By the way: To de-solder it often helps to use new solder. This improves the thermal connection between the solder iron and the joint. Flux usually does not help here much. Just do as you would solder the joint and while the solder at the joint is molten suck (using wick or a sucker) the solder away.By the way 2: Why do you want to replace the jack anyway? From the pictures the one looks OK.

author: Charkel
author_rank: Contributor
timestamp: January 12, 2018, 08:59:47 pm
content: The current connector doesn't work very well.New Connector:14.2V when red probe on back pin and black on front. Nothing on side pinOld on Board (can get some connection when plug in the right angle):I measured the volt and all the pins accept for the bottom one gives 14.2V when you hold the red probe on the middle pinThe bottom pin shows 10-14V.What does that tell me?

author: Twoflower
author_rank: Frequent Contributor
timestamp: January 13, 2018, 10:14:53 am
content: OK, now you know on the new connector the polarity and on the old one too, don't you? The pin with no signal can be left open in your application.

author: Charkel
author_rank: Contributor
timestamp: January 13, 2018, 02:05:56 pm
content: I am really new to electricity. Is this correct? And what is the last pin

author: Twoflower
author_rank: Frequent Contributor
timestamp: January 13, 2018, 04:16:37 pm
content: As I said. From the pictures it's not easy to see because the flux you applied. remove the flux and make a new picture again to see what the ? pin is. From the picture I would guess it is also connected to GND.The ? pin on the new connector can be ignored (left open). It is used for other applications to detect if a plug is inserted or not.EDIT: Something that came to my mind. Can you actually check the resistance between the ? pin and the other two without a plug inserted? It could be that the cable is a actually three pole not two wire. The third one is used for communication.

author: Bushougoma
author_rank: Regular Contributor
timestamp: January 15, 2018, 05:48:13 am
content: Quote from: Charkel on January 13, 2018, 02:05:56 pmWhat pin is positive and what is negative is relative to the application does the device have a positive or negative tip? There is usually a diagram somewhere near the jack or on the product label.It's better to use the term barrel (for the outer shell of the connector) and center pin (for the inside terminal).The ? pin is a normally closed switch it is commonly used to power a device from either battery power or from an adapter but not both.With nothing plugged in you should have continuity between the ? pin and the other pin that connects to the barrel of the connector now plug in an adapter (without power applied) and you should have no continuity between those two pins.In a battery powered application you would connect the battery to the ? pin with no adapter connected the switch is closed and the battery will power the circuit. When you plug in an adapter the switch opens, the battery is disconnected from the circuit, and the adapter now powers the device.The schematic symbol for a DC jack shows what I mean:https://electronics.stackexchange.com/questions/2381/deciphering-a-dc-jack-schematicIn the diagram at the link above Pin 1 is the barrel of the connector, Pin 2 is the switch, and Pin 3 is the center pin.If there is no continuity between the two pins then odds are the extra pin isn't a switch and is being used for data possibly adapter identification.I had an old Dell laptop that had a simple 3 pin Dallas microcontroller in the adapter they used the tiny center pin to send serial data to the laptop if the motherboard didn't receive the data (often due to a broken pin in the adapter connector) or didn't like the data it saw it would refuse to charge the battery and the BIOS would throw an error message.