Solder pad missing, where to solder to?

Thread Starter

MCristofaro

Joined Mar 13, 2018
9
Hi Guys
Im trying to repair a TV which had a faulty DC jack. I have removed the jack but unfortunately the solder pad has come of. I would love it if someone could please look at the pics i have attached and see if they can work out where i should solder it to. in one of the pics, where the solder pad is missing there is what looks like a trace (not sure if the terminology is correct) it looks like it goes to the round thing (technical talk!) i have an arrow pointing to where i think it should go. am i right? if you need more pics, just ask.
thanksWIN_20180314_13_07_50_Pro_LI.jpg WIN_20180314_13_04_11_Pro.jpg WIN_20180314_13_03_58_Pro.jpg WIN_20180314_13_03_58_Pro.jpg WIN_20180314_13_07_50_Pro_LI.jpg WIN_20180314_13_07_50_Pro_LI.jpg WIN_20180314_13_07_50_Pro_LI.jpg
 

Alec_t

Joined Sep 17, 2013
11,896
There's a good chance the two parallel pads were at the same potential and the missing pad won't make any significant electrical difference, although it would have served as a mechanical support for the connector.
 

MrChips

Joined Oct 2, 2009
22,900
Two pads at right angles appear to be the GND connection. The pad you indicate appears to be the +V power input.

Your photos lack proper contrast and magnification to see any missing pad and the likely connection.

Try zooming in at the connector area and don't allow the black case of the unit to influence the exposure of your photograph (i.e. there is too much black in the photo and it is offsetting the exposure causing over-exposure of the circuit board).
 

Thread Starter

MCristofaro

Joined Mar 13, 2018
9
I have attached 2 more pics, hopefully they are clearer. in the pic where the components are on the top near the DC jack it says Con6 and it looks like it connects to CA15, on the other pic i have drawn a line where i think it should connect to, is it right?
thanks
 

Attachments

MrChips

Joined Oct 2, 2009
22,900
I don't see any missing pad. The pad you are pointing to is the +V input from the power jack. It is connected to the large capacitor via a large trace on the top side of the PCB. Confirm this by doing a resistance check.

Looks like the same pad is shorting out to the GND plane. Clean around the perimeter of that pad on the bottom side of the PCB. Make sure there is no short to the GND plane. Do a resistance check.
 

Thread Starter

MCristofaro

Joined Mar 13, 2018
9
Thanks, so it is connected to that capacitor, CA15 is the solder point which i drew a line to right? there is another one right next to it. the pad is missing because i saved it when it came off.
 

MrChips

Joined Oct 2, 2009
22,900
Look carefully at the bottom side of the PCB (solder side).

1 - This is plain exposed copper. The solder mask has been inadvertently stripped off exposing the copper plane.

2 - The green layer is a layer of lacquer called solder mask. This prevents solder from adhering in the wrong places.

3 - If you look closely at these pads you will notice radial connections to the GND plane. These are called thermal reliefs and allow soldering to pads without allowing the heat to be sucked away by the large copper plane. These pads are all electrically connected to the GND connection and can be confirmed with a resistance test.

4 - This is the connection to the +POWER input connector. There should be no connection to the GND plane and can be confirmed with a resistance test between the +POWER pad and GND. Since you will be measuring across electronic components, including high value capacitors, you will observe some current flow. However, the resistance reading should be in excess of 100 or 1000Ω. If there is a short circuit to GND the resistance observed will be less than 10Ω.

Inspect carefully around this POWER pad. There should be clear separation around this pad away from the GND plane. Since this is covered with solder mask there should be no problem. However, if the solder mask has been damaged, make sure that there is no solder bridge between the pad and the surrounding GND plane. Use a soldering iron tip and some solder wick and quickly go over this area to remove any traces of solder beads or bridges.

Confirm with a resistance check between the POWER pad and GND.



20180315 PCB.jpg
 

Thread Starter

MCristofaro

Joined Mar 13, 2018
9
i think i understand now. when i solder the pin from the DC jack i need to make sure that the solder does not touch the exposed copper or it will short. ill solder from the power pin to the CA15 connection on the back. the other two pins should be fine. i might be better off painting or covering the exposed copper near the pin.
anything else i need to know? nearly forget, its definitively the round solder join i need to solder to and not the square one?
 

MrChips

Joined Oct 2, 2009
22,900
Before you install the replacement power jack you need to clean out the solder in the holes of the connection pads (the three large oblong pads). Otherwise you will have great difficulty inserting the power jack.

There should already be copper trace (on the top side of the PCB) connecting the +POWER connector to the +VE lead of the large capacitor CA15. Confirm this with a resistance check between the +POWER pad and the SQUARE pad of the capacitor.

There is no need to make any extra connections (assuming that the plated through holes at the +POWER pad is not damaged).
 

Thread Starter

MCristofaro

Joined Mar 13, 2018
9
I guess this would work. What if I just hardwired the AC cable to the PCB? I could solder the red to the square and the black to the negative then add something like a rubber grommet to the AC cable to stop it from getting pulled out. Is that a I really need to do? All im really doing is bypassing the AC jack.
What are your thoughts on this?
 

Alec_t

Joined Sep 17, 2013
11,896
It's a DC jack, not AC. Use the jack. Soldering stranded wire at those positions would be asking for trouble. A stray strand could cause havoc.
A grommet would not provide adequate anchorage.
 

Thread Starter

MCristofaro

Joined Mar 13, 2018
9
Alec_t i see your point, its not an AC jack. the cable is not just a straight through cable its a DC\AC adapter like you get with laptops so its doing the converting i take it. by the time the power comes out the tip its DC??
 

LesJones

Joined Jan 8, 2017
2,959
Members can only give answers on the information you supply. So if you give false information the answers will be of no value. Also a statment like "i take it. by the time the power comes out the tip its DC??" is no help. You need to verify information, not just take a wild guess. So you need to be able to say the supply is so many volts, AC or DC, The polarity of the pins on the connector and the maximum output current rating of the supply that you are using. (You would have also to supplied the nature of the power requirement of the item.) IF you were talking about using the original supply then you should have said so as we would then known the rating was correct.

Les.
 

coho

Joined Mar 20, 2018
1
IMG_20180319_120801.jpg s-l1600.jpg

hi guys,

don't mean to hijack a thread, but seeing as I jumped into the forum to create a thread with EXACTLY the same question, I figured it'd only make sense to piggy back my request.

My problem is identical - during the process of replacing the left mouse switch (Omron D2FC-F-7N) in my Razer Deathadder mouse, one of the solder pads/annular ring lifted. They used a very dark black solder mask which made it near impossible to see underneath even after cleaning with alcohol and acetone. After physically scraping the coating away trying to follow the conductive path where I could reconnect the circuit to i'm left scratching my head... ... ...where was it connected to? I'm leaning towards the closest/right most trace but....i have no way of knowing.

Any pointers would be greatly appreciated.

Cheers

Coho
 

Thread Starter

MCristofaro

Joined Mar 13, 2018
9
with mine, i found a trace on the top of the PCB. You may have already seen the pic above. im advised to solder to the square pad witch is positive but after checking the board yesterday the other pads on the board which are square are negatives so now im scratching my head too. hope yours works out better than mine!
 
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