Solution for AC Adapter not recognised problem, and loose power plug

I have several XPS m1530s and several Dell PSUs. Two recent additions to the stable reported the famous "The AC power adapter type cannot be determined".

I found the reports of BIOS updates, broken data wire, failed DS2501 1-wire PROM, broken power socket, etc.

I decided to investigate one unit. I stripped it down and removed the I/O PCB that the power socket is mounted on. I then inspected the data circuit and tested it for continuity.

There is a test point (TP) on the underside of the PCB just after a via (through-hole) from the upper side. I tested between the TP and the data pin of the socket without finding a signal. I assumed the issue was a solder dry-joint so I flowed new flux and solder top and bottom of the PCB for the data pin. That failed to fix the problem.

I found the signal on the edge-connector from the TP, and by carefully scraping away lacquer was able to test from the underside of the via to the TP. There was no signal between TP and the centre pin of the socket, nor from the underside of the via. At this point I suspected the via was faulty.

I then scraped the lacquer away from the top side of the via and found the signal from the TP there too, so the via is good.

There was no signal between the top side of the via and the data pin of the socket - a distance of about 10mm. I carefully scraped more lacquer away close to the data pin but just before the screen printing. The signal reached there too, but did not get from there to the data pin - a distance of 2mm.

I then carefully scraped more lacquer away on the final 2mm of the trace connecting to the pin. I thought I'd find a break and have to solder across it.

In the event the simple act of firmly scraping (with a 2mm jewellers flat-bladed screwdriver) fixed it. I tested again after scraping and the signal was working.

Inspecting the socket closely when the plug is inserted and removed I noticed there is a distinct physical flex of the socket against the board, and the data pin definitely stressed the via it is inserted through.

It seems that flexing is enough to make an invisible break (even the microscope couldn't see the break) but physical pressure can fix it in some circumstances.

I hooked up the LCD to the LVDS and the power switch/indicator PCB to the motherboard and applied power. The system started without the warning. I tried all the PSUs that it had previously been reporting as 'bad' and none of them cause the error report any more.

I shall make sure of the repair by soldering a flexible wire directly from the data pin of the power socket to the top side of the via to prevent a recurrence. I shall be working on the other 'faulty' m1530 tomorrow and hopefully find a similar solution.

I thought others might find this information useful since it is another possible solution if the PSU itself is known good.

P.S. I also found a solution to the loose power plug issue. The power socket has 4 flat sprung-metal lugs around the centre pin which protrude away from the centre pin and press against the internal surface of the power plug to hold it firm.

There are 4 very small slots in the centre pin plastic where those lugs expand to. By carefully applying pressure with the 2mm jewellers flat-bladed screwdriver to the ends of the lugs in those slots I was able to force the lugs to move backwards slightly and make the lugs protrude slightly more. That was enough to hold the barrel of the power plug firmly again.