Solder on mother board melting - Page 1
Forum section: electronics / general

author: G7PSK
author_rank: Super Contributor
timestamp: September 06, 2012, 03:55:48 pm
content: I replaced the socket on a HP laptop about a month ago, today the owner brought the thing back showing the same symptoms as before, would not turn on or charge the battery, I took it apart and found that the solder on the center pin had melted. The laptop was being used with one of those universal power bricks and the plug was not fitting tightly enough on the pin in the socket. Any one else come across this problem before.

author: deephaven
author_rank: Frequent Contributor
timestamp: September 06, 2012, 04:05:49 pm
content: Quote from: G7PSK on September 06, 2012, 03:55:48 pmIf it was the connector I'm thinking of, it's available in two different sizes of inner pin - 2.1mm and 2.5mm, it might be that the power supply is fitted with the 2.5mm size and the laptop has a 2.1mm pin.

author: Short Circuit
author_rank: Frequent Contributor
timestamp: September 06, 2012, 04:28:43 pm
content: Overheating of connector terminals because of lousy contact is a fairly common phenomenon.Usually because of spring tension being worn out, but a sloppy fit like this socket+psu has the same effect;increased contact resistance, much higher current than intended (usually generic 2.1/2.5mm contacts areintended for just ~1amps instead of 4-5amps of a laptop charger) and significant temperature rise is the result.And a start of a vicous circle since that increases contact resistance even more, weakens spring tension,more temperature rise, etc. Up to the point of solder melting or plastics catching fire.

author: AndyC_772
author_rank: Super Contributor
timestamp: September 06, 2012, 06:09:06 pm
content: Those concentric dc power jacks are awful, horrible connectors. I've lost count of the number I've come across which have misbehaved, fitted badly or been specified just because they're expected rather than because they're actually suitable for the job.My laptop has a 180W supply and can deliver over 9A - yet it's still using a crappy concentric connector. No way is it rated for the job.

author: G7PSK
author_rank: Super Contributor
timestamp: September 06, 2012, 08:21:19 pm
content: Why is that such sockets and plugs are used there must be better out there,if not surely the computer manufacturers have enough purchasing power to make a better one. It the same with the wheel chairs and mobility scooters the industry standard for the charging has become the XLR plug and socket this as far as know was designed for microphone connection now it is being used as a power plug at somewhere between 4 and 10 amps. Although they do hold up better than the tatty things on laptops.

author: Monkeh
author_rank: Super Contributor
timestamp: September 06, 2012, 08:39:18 pm
content: Quote from: G7PSK on September 06, 2012, 08:21:19 pmXLR's used for a lot of things, it wasn't developed for mics. Good ones are fully capable of handling 15A.

author: zaoka
author_rank: Frequent Contributor
timestamp: September 06, 2012, 08:48:54 pm
content: You have to replace both at the same time (plug and jack), otherwise, it will not last very long. To prevent this from happening again get little extension for power cable, its available from ebay for both 2.1mm and 2.5mm.I install one and supply customer with extra one.If they ever forget to disconnect cable it will not brake the jack again, it just disconnect from extension...Also make sure that filtering capacitors inside of AC adapter are OK. The best way to test it is to use resistor load to match amps and measure with scope. Alternative way is to connect ESR meter to DC side of AC adapter and make sure there is no high ESR.I usually repair AC adapters by replacing DC plug and installing good quality one + I enhance with thick shrink tube made for these plugs.

author: ablacon64
author_rank: Frequent Contributor
timestamp: September 06, 2012, 11:48:38 pm
content: The connector must be very tight or it will overheat and cause problems again.

author: G7PSK
author_rank: Super Contributor
timestamp: September 07, 2012, 07:35:08 am
content: I have told the owner to buy a new power brick, as being the best option also the cheapest if you have to pay some one to change the plug as they would.

author: amyk
author_rank: Super Contributor
timestamp: September 07, 2012, 09:15:18 am
content: Quote from: G7PSK on September 06, 2012, 08:21:19 pmThey use them because they're cheap. Consumers who know nothing about ampacity want thin and light.At least the concentric connectors are a little better than Apple's tiny magnetic plug, which has absolutely no wiping action and relies on plain contact pressure.

author: Psi
author_rank: Super Contributor
timestamp: September 07, 2012, 09:29:46 am
content: Quote from: deephaven on September 06, 2012, 04:05:49 pmTotally agree, this is likely the issue.