Identifying the Real Problem (DC Jack)

[DanF]

How is it possible to identify the exact problem when having DC jack issues?

I know I am able to check the functionality of the actual jack by using a multimeter to measure the voltage in and out of the jack. However, I've had cases where when the adapter's pin is pushed slightly down (must be held down) the jack works... otherwise it just won't work.

The following is a question I'm asking due to lack of experience in such repairs. Ever had a case where the problem was the connection rather than the jack itself? I'm asking this since spare parts take ages to arrive where I'm from, and this would save the client from waiting ages (and I'll be able to give a more efficient service).

Thanks

 

[mraikes]

Sure - if the jack itself is breaking loose from the solder holding it to the motherboard (and completing the circuit) the symptom can be exactly as you describe.

In fact many of the jack problems I see started out just that way. Then the customer figures out that a little pressure will make it work, so instead of bringing it to me right away, they figure out ways to keep the pressure applied. Folding the cord back under the laptop, setting a book on the cord to push it down, etc. Of course that eventually causes even more damage and eventually stops working completely. Then they come see me.

 

[NJW]

I've had cases where when the adapter's pin is pushed slightly down (must be held down) the jack works...

if the jack itself is breaking loose from the solder holding it to the motherboard (and completing the circuit) the symptom can be exactly as you describe.

If you can catch it early enough, simply reflowing the solder joints can be a permanent cure (a touch of flux and solder will help).

A simpler initial check for a standard power jack, without a small centre pin, is to look down the end of the plug (coming from the charger). The centre contact is usually a two-pronged fork – you'll see what looks like two contacts on opposite sides of the plastic insulation. Take a dental pick or sewing needle and gently ease those two contacts towards the centre of the hole. If you're lucky, that just might be it.

 

[Larry Sabo]

The centre contact is usually a two-pronged fork – you'll see what looks like two contacts on opposite sides of the plastic insulation. Take a dental pick or sewing needle and gently ease those two contacts towards the centre of the hole. If you're lucky, that just might be it.

Yeah, that's a good tip. I'm working on an ASUS BU400A with what was reportedly a DC jack problem, and had to bend the two pins that contact the plug inner metal sleeve outward. Stupid jack on that model has another set of prongs that contact the outer sleeve of the plug and they will get stuck in recesses of the jack body if you happen to push them outward too much (see here). I just finished adjusting such a jack only to find the laptop will still not show any sign of life in spite of good jack solder joints and having 19v on those leads. Apparently it was a DC jack and a MB problem. The laptop is reportedly still under a 3-yr warranty and they had me fix it rather than wait two weeks for WorstBuy repair it. I guess all I'll get out of it is a diagnostic fee.

 

[DanF]

Thank you all. Very informative, thanks. The contacts of the non-pinned jacks is definitely a new one for me.

Just desoldered a jack... took me 3 minutes to get it out, using the hot air station I just got, and over an hour to clean the remaining solder :/ I hope this is normal for a beginner haha

 

[Larry Sabo]

Solder wick and a good iron (50-70 watts) while the MB is still warm should reduce the clean-up time to 5-10 minutes. Add a little flux, if needed.

 

[NJW]

over an hour to clean the remaining solder

To state the obvious, this is too long! Apart from the time wasted, you are running a real risk of damaging the m/board. Work hot (which is perhaps counter-intuitive) and work fast.

I prefer a solder sucker to braid, but it's a personal choice. With hot air, don't bother trying to remove solder first – just heat all the pins and remove the old jack socket. Now change to the iron (@Larry Sabo gives a good guide to the power rating, imo) and apply solder (and flux, or use a cored solder) to all the now-empty holes. This is important. You can now clean each hole, one by one, with the iron and [braid|sucker]. If you use braid, add some flux to each hole before cleaning.

Occasionally, an obstinate hole will just refuse to clear sufficiently to insert the new jack socket. A fine stainless dental pick or sewing needle can be useful to gently clear the solder, while heating, enough for clearance.

 

[Larry Sabo]

I sometimes use a solder sucker, but find that solder bits sometimes fall from the opening onto the MB, which could cause a short if not thoroughly removed. If you get one, I'd suggest you get a good one and cut a small notch in the tip to make it more effective at getting the tip right into joints with through-hole leads.

 

[jbartlett323]

Yup, too long, too hot.
I continue to use my rework station for cleaning the holes. Put a little heat too em, Suck em out with my solder sucker (http://www.amazon.com/gp/product/B0012YJ3HO/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 - Never could figure out braid) Pick the holes with a pick if needed, clean em with some alcohol, tin the holes. Switch to Iron and attach new jack. Whole process should take about 20-30 min Max. Machine tear down adds 30min-1hr depending on machine. I usually have most Jacks jobs done start to finish in just over an hour...

 

[DanF]

Was too late... didn't last an hour cause I had to assemble the station for the first use So the hour includes the assembly (more like 30 mins, honestly).

I've attached an image (may not be the clearest, taken with a phone). But you might be able to give more feedback

 

[jbartlett323]

Wow! You went for Really Clean!
I don't usually go far enough to leave scratch marks. Just get the better majority, make sure its not in the holes, no big chunckies, and nothing left I can pull across the hole with a hot iron, more or less. You actually want a little tin left there, as it is easier for solder to adhere to solder than it is to fresh copper. But on the other hand, you want as much old off as possible to get rid of oxidation.

 

[DanF]

Yes, pressed a little too much at some places, especially the holes at the top. The port next to the DC jack is an Ethernet port, so I was extra careful with the hot air iron. It was covered with foil, but still could smell plastic burn... so I decided to finish it off with a soldering iron with the help of flux.

For some reason, I couldn't get the soldering off those particular holes at first, then I noticed the soldering iron's temperature was at 300. I then increased to 400 and it got sucked easier. Is 400 too high? I tried not to leave it on the board as much as possible.

Thanks again for your feedback.

 

[NYJimbo]

Is 400 too high? .

When I do jacks I always keep my iron pegged at 480c.

 

[DanF]

Thanks... good to know

 

[DanF]

Soldering done... although I must say that I'm not yet impressed with my skills haha. The blobs look huge compared to the other solder points on the motherboard.

 

[jbartlett323]

Yeah those are some blobs! Your contacts weren't hot enough when you applied the solder, therefore it did not flow. not a good connection. I would remove the solder and try again... More flux might help a bit...
Typical of newbie soldering though so your good!

 

[Larry Sabo]

Yeah, looks like not enough heat and not enough/any flux was used. I'd suggest wicking it up and trying again, with flux on the board first and holding the iron on the joint after it has melted, until the solder flows right into it. Hold the iron on the joint a few seconds longer than looks necessary, and clean excess solder off the tip before starting to solder every joint. Actually, you're doing really well considering this is your first DC jack.

 

[jbartlett323]

and clean excess solder off the tip before starting to solder every joint. .

Great point that I hope you already know! Clean that tip often! Can't really clean it too often. What cleaner do you have? A sponge, a steel-wool thingy, or something else? An unclean tip doesn't allow heat to transfer, therefore not allowing you to get your contacts to get to the proper temp.

Also when your done, be sure to leave you tip "tinned" aka with solder on the entire tip, so the tip itself doesn't oxidize and get ruined! I had to learn that one the hard way...

 

[DanF]

I'll give it another try. What if one of the blobs makes contact with the jack? Answers to your posts below:

I have a sponge not the steel-wool stuff.

I am putting some solder on the tip and clean it in the sponge before starting.

I did a mistake not to put any flux before soldering.

What do you mean by leaving solder on the entire tip when done? Does that mean that I should turn the iron off with solder on?

 

[NYJimbo]

Yeah, blobs are a sign of a cold solder joint. You want more of a tent which you kinda have on the pin on the far right. Always flux a little, then apply the soldering iron to the side of the pin and then the solder to the pin so that the solder FLOWS into the pin and hopefully into the hole.

The desire is to be able to see solder through the hole on the other side. If you can get some tiny amount of solder to flow up the other side that's the sign of a great solder job. For example:

You see the center pin in the back of the jack has a decent flow of solder from the other side
and the pins one the side and back (very tiny 2 & 3 marks on mobo) have solder flowed through as well.

A clean mobo, good flux, high enough temps and knowing how long to hold the iron to get the flow makes for a perfect
jack job and it will be stronger than the original.