strong thermal glue for laptop DC power jack?

[bvanevery]

A friend of mine has a Lenovo G580 laptop with a physically broken DC power jack. Little kids jammed power plugs into it fairly hard, and over time, the very limited amount of plastic that was holding the housing together simply broke. It also snapped the small tab that conducts electricity from the jack's center pin to the board.

I have offered to try to repair it for free, since the laptop belongs to an 11 year old boy who's about to start learning computer programming and HTML. I started at the same age, albeit with an Atari 800. He doesn't have a laptop currently, is saving for part of one, but he doesn't have much money and this old one is fixable. They just didn't know who to send it to, and were going to get fleeced for $200+ worth of repairs, not worth it compared to the value of the laptop.

The jack is not actually on the motherboard proper. It's on a mini-board, about 1.5"x1", that also contains a USB port and then runs by a cable to connect to the main motherboard. The part number is 55.4SH03.001G. It is surprisingly difficult to source this miniboard in the USA; if I were in Russia, I'd have it sorted. I've been looking and looking but haven't found a supplier.

I could buy a new DC jack for a few bucks, then solder that on. However I haven't run down exactly which DC jack is required, and the internet searching is getting tedious.

Complicating the process, is I'm finding a lot of confusion in vendor part catalogs about what "goes with" a G580. Even the vendor's hardware repair manual is confusing on that point, as it covers several models and some of those seemed to have better designs, where the DC jack is just a dumb separate component on a cable and doesn't have any special miniboard.

So, I have thought of repairing the existing miniboard and jack I have in front of me. Aside from the soldering work, I would need some kind of strong glue. It would need to adhere to the plastic, not do anything electrically unpredicatable, stand up to thermal stress. I don't *expect* this part of the laptop to get very hot, but who knows, and I don't want to have to do that job again. Is there such a glue, or am I barking up the wrong tree and should just get on with identifying exactly the right DC jack to replace?

The repair cannot be at risk of starting a fire. I'm a careful guy, I will do things "right", but I thought I'd ask about that risk with this proposed method.

Bonus: can the glued part possibly be stronger than any DC jack replacement, and thereby stand up to the little kids better? I'm sure losing their laptop for over a year will have an effect on their behavior, but who knows.

 

[Jagtech]

I doubt you will have much success with gluing the old connector back together. The kids will destroy again it in milliseconds. If you can't find an exact replacement, then how about just soldering in a short pigtail to the board with an in-line connector on the end? It would hang out the back about 1", and be easy to replace if it became damaged again. Of course, it would need to be anchored inside the laptop so it can't be yanked out.

 

[davenn]

I tend to agree with Jagtech on that one
and it wouldnt be the first time I have mounted a power or other connector on a short length of cable outside a piece of gear

cheers
Dave

 

[KrisBlueNZ]

I agree with Jagtech too. Don't try to reconstruct the socket.

My first option would be to try to find a replacement socket that fits (or can be made to fit) onto the daughter board, and that fits the plug on the adapter. There's quite a variety of dimensions for the standard style DC connector, so bring the adapter and the daughter board to a electronic component shop and do some trial and error.

Shops like Radio Shack probably won't have much variety - at least, not on a shelf that you can try out. You might be able to find a more specialised shop, perhaps at a nearby larger city (if you don't live in a big city).

Alternatively, you could order a whole lot of sockets from a company like http://www.digikey.com or http://www.mouser.com and hope that one of them is suitable.

You can measure the outside diameter and length of the plug to eliminate some of the sockets, so you don't end up buying a dozen of them!

Your next option would be to replace the plug on the adapter as well, with one that matches a suitable socket. This is not really a good idea because DC plugs that you install yourself onto a cable don't normally come with decent strain relief and tapered support to ensure a good bend radius on the cable, so cables tend to break or short out at the entry to the plug's backshell.

You might be able to find a complete cable with moulded plug, with a matching socket, and replace the whole cable from the adapter.

As for glue, as long as it won't get too hot, I would recommend hot melt glue. It is pretty sticky, it fills gaps very well, and it's pretty strong (unless it gets too hot). You could use bits of card to build some walls around the area with the socket, and fill it all up with hot melt glue. (Make sure the socket doesn't have any gaps in the back or sides though!)

That stuff sets almost like potting resin and will grip onto all of the plastic. As long as the socket is strongly made, I doubt that you would ever have a problem with it after that.

If you upload some photos, we might be able to be more specific.

 

[bvanevery]

Dangling things externally sounds neat, but would have to be made yank-resistant or fail gracefully and cheaply when competely yanked out, because we are talking about use by kids again, not careful adults. I see someone's shoe hitting the floor next to the laptop at the wrong moment and that's all she wrote. Over time, I'd even expect an adult to find a way to bash the end of a cord into a hard and unexpected surface somewhere, like a refrigerator handle, a counter edge, or the top of a chair.

Wires also get strained over time. All of my Dell AC power bricks have died because of strain at the base where the DC wire goes into the brick. They're soldered on and either it breaks there, or the 3rd proprietary control wire breaks because it's a fine wire and the brick exerts a bending action on it. Nobody cares because Dell used to make $60 a pop on this fundamental design flaw, and now the Chinese sell their knockoffs for $8 which last about a year.

For most people's use, as compared to my own careful use, I think there's a reason things are generally recessed and protected inside a case. Too bad they designed this socket to take force like crap. Pretty much the internal equivalent of those external AC bricks I hate. Worse, because that daughter board isn't findable.

I will try to source a new DC jack. Maybe there's an electronics supply place in town if I search hard enough.

I also need to figure out why my cheapskate Walmart 30W soldering iron will not melt the solder on this daughter board. One theory is I've never tinned it, because I'm a noob, so it's badly oxidized and that's interfering with its heat output. Another is it's a piece of junk. A third is I haven't learned about higher temperature solder. Seems to melt regular solder well enough.

 

[KrisBlueNZ]

... now the Chinese sell their knockoffs for $8 which last about a year.

These should be outlawed. In fact, they are, but no one takes responsibility for checking for them. Often the mains power leads use less than half the wire thickness they should, and the insulation can break when bent. That's a huge fire hazard.

There's an interesting article from the UK at http://www.wandsworth.gov.uk/news/article/11603/fire_risk_from_cheap_phone_and_laptop_chargers and a page at http://ec.europa.eu/consumers/safet...essionid=090091cfc8a304b06c3148c4533252f1e574 that lists safety standards violations from around Europe for most categories of products.

Most violations are actually for children's toys, but there are plenty for electrical appliances such as lamps, battery chargers, cellphone chargers and laptop chargers. Most of the flagged products originate in China, with a few from Hong Kong.

I also need to figure out why my cheapskate Walmart 30W soldering iron will not melt the solder on this daughter board. One theory is I've never tinned it, because I'm a noob, so it's badly oxidized and that's interfering with its heat output. Another is it's a piece of junk. A third is I haven't learned about higher temperature solder. Seems to melt regular solder well enough.

You shouldn't be using high-temperature (lead-free) solder. It's only mandated for manufacturing, not for rework, AFAIK. And it doesn't do as good a job as leaded solder.

If the tip doesn't tin properly, try cleaning it with something like a pot scourer - a 3M Scotch-Brite or a "goldilocks". A file or emery paper will remove the plating - assuming it has any! If you're going to dump it anyway, you might as well do that, if the pot scourer doesn't help. Also Google the relevant keywords for more (better) advice.

 

[bvanevery]

You shouldn't be using high-temperature (lead-free) solder. It's only mandated for manufacturing, not for rework, AFAIK. And it doesn't do as good a job as leaded solder.

I've got regular solder. It's the solder already on the daughter board I can't melt. Seems to be really tiny amounts of really precision stuff, a watchmaker's level of accuracy. Not a hand done job at all.

 

[KrisBlueNZ]

Oh, sorry! Right, it can be hard to melt solder on these boards because there are large amounts of copper around the socket connection points on both sides of the board, to strengthen the socket mounting.

It may help to cut the metal leads of the socket off flush with the board, using side cutters or a hacksaw, or break the plastic of the socket then bend the pins left and right until they break off. With less metal to absorb your soldering iron's heat, you may be able to melt it enough from above to pull the remaining bit of metal out from below.

You can mix leaded solder with unleaded solder and this will lower its melting point - once you've melted it initially so the two types of solder can mix together. So you could try holding the iron against the top side of the board for, say, 10 seconds, then trying to feed in some leaded solder where the two are touching. Once it starts to flow into the solder on the board, things should improve.

Once you've melted it, you should be able to clear the solder out of the holes using a solder sucker, or by melting it then quickly whacking the board down onto something hard so that inertia pulls the solder out.

If you decide to get a better soldering iron, a temperature-controlled one is worth the investment IMO.

 

[bvanevery]

Large amounts of copper sounds about right. I could feel the heat spreading through the rest of the board, not focusing where I wanted it.

 

[KrisBlueNZ]

Right. I think that will be unavoidable. If you have a powerful heat source such as a big soldering iron, you may be able to heat up the power socket area to melting point quickly enough that the heat doesn't spread too far, then pause while it all cools down. Also you may be able to identify components that will be damaged by heat, and either remove them temporarily, or heatsink them somehow.

Anyone else have advice here?

 

[bvanevery]

I removed the DC jack by grinding some of its pins with a household drill and a tiny drill bit. The drill had a forward pistol grip handle that I was able to fold so that it was stable on the table. I just rubbed the offending parts against the drill bit until they sufficiently gave way. I used the rocking back and forth method to finish it off. This approach was quite destructive, I don't have a DC jack anymore, and for sizing a new one that's regrettable. However it does have a code stamped on the side of it: 120709+17.

Even having removed all that extra stuff, the solder around the pin stubs left in the board will not melt at all. This board seems to be too tough for my Walmart 30W soldering iron.

 

[KrisBlueNZ]

Bummer. That code doesn't mean anything to me, and would be hard to search for unless you know the name of the manufacturer; even then, there's a good chance you wouldn't discover anything useful.

Re sizing the new one, you could bring the whole laptop, including the daughter board, into any shop. And you can measure all the dimensions to compare to any part you find online.

I guess you'll need to find something more powerful than that soldering iron. Perhaps you can borrow something.

 

[bvanevery]

I can buy a new iron, but the question is, will that solve the problem? I don't want to lay out the money for something that leaves me in the same predicament.

 

[KrisBlueNZ]

I guess that depends on what you buy. My guess is you'd need something rated at 50W, maybe more. I wouldn't buy one unless you think you'll have other uses for it.

I don't have much doubt that you'll be able to melt that solder if you can get enough heat onto it. It's up to you how you achieve that.

 

[(*steve*)]

It may be unleaded solder (higher melting point) and internal power planes (large heatsinking effect).

Together this means you need quite a bit of heat and even more care because you don't want to damage anything.

Can you give us some photos of the area of the board you're talking about?

 

[lashortee]

hi all!.. i want add that i would buy a ac jack to avoid complications later, iam not a pro but had my share on this issue..go to ebay type model and device and write ac jack by it..cost like $3.00 no more than that a bad solder or hard heat could damage even more..safe than sorry!..i buy ac/dc jack from there very often

 

[bvanevery]

I learned more about thermal bridges, or lack thereof, and went at it again. I hacked a soldering tip with a much larger surface area, suitable for pressing pins out from the backside of the board, by simply turning my cone tip backwards in the iron. This leaves a big circle of metal as my soldering tip, and it's much hotter. I did some scorch damage to the board but it was successful at pushing the pins partially back through the board.

The pins were still in the board though. Another thing I did, which I'm not sure was helpful in hindsight, was drip regular solder into the holes from the back of the board. I dripped enough solder to make "solder icicles" on the other side of the board. I became pretty jaded about making any kind of a mess, because my solder would tend to ball and not adhere to much of anything for some reason. I don't know if it's the solder, the coating on the board, the temperature I'm working at, the clumsiness of my cone tips, or what, but I was chasing an awful lot of little balls of solder around without getting it to go anywhere. Eventually I was like, who cares, this stuff will never stick for a darn, let's just flow a ton of it and see if it changes the temperature of whatever's already in the board.

I think that depressing the pins flush with the back of the board was the more helpful tactic. After that, I changed back to cone tip and shoved it into the slots so formed. I think it had greater thermal contact than when the pins were an "outie". I went so far as to dig some minor holes in the back of the board. I hope that is no great harm. I was more worried about not messing up the copper joins at the sides of the board holes, as I read a tech doc somewhere that destroying the side copper is a common soldering error, generally from using too much force on pins. Better to gouge plastic than to mess up copper sides, I figure.

Once I had heated the holes from behind with the cone tip, I rapidly flipped it over and scraped at the front of the holes, while the solder was still somewhat molten. This took some dexterity and learning curve so as not to scorch my fingers. I also nearly broke a plastic coupling on the front side of the board with my screwdriver, before I realized I'd have to be careful and dextrous about such flipping maneuvers. Once flipped, scraping at the front of the board with my cone tip was generally sufficient to dislodge the remaining pin parts.

Then I had a lot of excess flowed solder to clean up. I haven't completely done it because I don't think it's a big worry yet, but I just sort of scraped at it with my cone tip, removing gross excess. I can get back in there with desoldering braid once I've got a new DC jack.

One thing that did not work, is trying to push the pins with wooden toothpicks while the solder was still hot. First, it was very difficult to make the switcheroo from cone tip to toothpick before everything cooled down too much. Second, my particular toothpicks were weak and for the most part would break. The back-heat, front-scraping method was far more successful.

Hopefully I've successfully removed the old DC jack without damaging the board in any functional respect. The board looks like a clumsy person went at it, but if it works it works.

 

[KrisBlueNZ]

Good! Do you have a replacement socket?

 

[bvanevery]

Not yet. I've observed the ebay listings per lashortee's recommendation, but haven't settled on that as the place to buy.

 

[(*steve*)]

I think you have a technique problem more than a soldering iron problem.

Hopefully you've not destroyed too much.

We need good photos before we can advise any more.