Lenovo Laptop Rectangular Pin Adapter Repaired
Got a call from the Customer that his laptop is not charging but when he plugged another adapter laptop is charging. His office is nearby my place so I told him to send the adapter to me so that I can check it. He sent the adapter to me. On primary Voltage testing it is confirmed that adapter is not working there is no Output voltage.
After taking conformation from him about repair I started diagnosis by visual inspection.
No physical damage found hence I opened the adapter for further inspection.
On PCB I did not found any damage or burnt mark. So I checked for 20VDC output voltage I found 20V DC on the output terminal where output DC wires are soldered that is confirmed adapter is working but either DC wire or connector is bad.
So I desoldered the wires from PCB and checked continuity. Earthing wire found ok but +ve supply wire is open circuit. So for finding the culprit I segregated the connector. From the wire. It is very complicated job because it is molded in plastic if you damage the connector you cannot complete the job. So eventually I managed to remove the connector safely.
I found wire soldered intact this adapter is having ID Pin & I found one resistor of 120Ω. Is connected between earthing and ID pin.
I am confused with color code of the resistor. On googled I found different value resistor is used in different wattage adapter.
So connector is in perfect condition now culprit is cable. I am not having this type of cable replacement with me. As this cable is having Ferrite Core on both the end of the Cable so I decide to keep the same cable if it is usable. So I connected only cable one by one on mains line for using my contactless line detector to find out the broken wire location.
But this time this trick is failed because due to Electromagnetic interference on shield of this wire around main +ve wire the LED of detector unit is glowing end to end it indicating no breakage of wire. (This Line detector only work where wire is single. may be misguide on twisted wire pair)
I used another trick to find broken wire location i.e. Puncture the cable using sharp needle on various ascending order on the cable.
Using this trick I connected one probe of meter on one end and another probe on Needle …..If meter is beeps that means from the end where you connected the probe to this location where Needle is inserted showing continuity and wire is ok. So I started to check from one end which is connected to DC output PIN.
So gradually I am moving ahead on adapter side here in between length of cable I found one location where I did not get the beep.
Again I punctured the cable backward direction step by step & testing on different location I found the location where I got the beep so that is the location of broken cable.
I cut the wire on that location just pulled the inner cable with hand and I found the broken wire on my hand it is hardly one inch away from the cut. Checked the continuity again now Wire showing the continuity on both the cut piece.
I joined the cable by soldering and insulating using heat shrink tube.
Checked Out Put Voltage on cable meter is showing 20VDC.
Connected the connector:
Checked Voltage after fixing the connector
Now Adapter is ready for pickup.
This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.
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Note: You can check his previous repair articles on Battery Eliminator 1.5V To 12V Modification