Completely Dead HQ Switching Adapter With Voltage Selector Repair
My brother had tried his HQ selectable voltage 1A output adapter on his Android Tablet. But he noticed that the adapter failed to charge his Tablet. Below this adapter model P.SUP.EU1000 is shown.
And he was glad that this failing adapter had not killed his Tablet in the process just trying to charge it. I was asked to check and find out why the adapter showed no output voltage when measured. Why also the red 3mm led (led Vo + marking on the pcb) was no longer active.
The case was easily opened by removing both special triangle screw (tri-lobular like) heads. And next by unclipping the case from the bottom half at the EU mains plug side, because no other screws were used. Which resembles the way in how many DMM meters and also IR remote control cases are closed and need to be carefully opened.
Immediately after I checked the board on the solder side I noticed the black smd component parallel over normal sized diode SB2100. And because those were completely shorted I started by removing the SK36 smd diode. That indeed was the culprit here! Of course I first had already checked the primary fuse F1 T1A/250V plus all primary Bridge diodes D1 to D4 that all were fine.
And after smd diode SK36 was removed the short over diode SB2100 was gone. And I started to test the adapter. Led led Vo worked and so did the adapter showing exact all selected voltages on the Tablet sized charger output plug. Those plugs can easily be changed by another adapterplug by just unplugging and inserting another one. Those are probably also included with this adapter but left my brother at home. Next photo shows the now removed culprit diode SK36. Made with my recently FW fixed G600 LCD microscope (see one of my previous repairs). Here the links to both diode datasheets: https://datasheetspdf.com/datasheet/SB2100.html
The shorting SK36 diode was probably used as a special protective 60V DC blocking diode and therefore needs to be replaced by a new diode. Which I ordered at the low cost of a six-pack.
Only the shipping cost were almost as high as the set of 50 new SK36 diodes did cost. I only needed one diode here so 49 diodes are spare new diodes for any future repair.
Above and next photos show the working adapter when set to its minimum 3V voltage, and to its maximum voltage of 12V.
This repair reminded me onto another similar repair that I did in the past that was also about removing a single protection diode. It was an article about a “Bad P6KE150A Transient Voltage Suppressor Diode In HP Power Adapter”. That adapter also worked again after that shorting suppressor diode was removed. Of course that adapter also got a brand new suppressor diode afterwards to make sure it kept working safely.
So this article was about another easily saved adapter and again working as new at almost no cost.
Albert van Bemmelen, Weert, The Netherlands.
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Note: You can read his previous article on Restoring A 47 Year Old Piezo Wireless FM Microphone