Electronics • SMPS Repair
Repairing Aldi LED Clamp Lamp Power Pack
A look inside the Aldi LED clamp lamp power supply – why it failed, how I diagnosed the fault, and how I brought it back to life.
⚠️ High Voltage Warning
DO NOT ATTEMPT THIS REPAIR UNLESS YOU ARE EXPERIENCED IN WORKING WITH 240 V CIRCUITS. If you don’t know what you are doing, THIS CAN KILL YOU.
Aldi LED Clamp Lamp
I bought 3 of these LED clamp lamps from Aldi in 2016. Their power packs are of inferior quality – one failed within a week, so that one was returned to the store. Then a second one failed after 6 months.
I couldn’t find the receipt so I thought I would just repair it and also have a look at the design. Who would repair a $15 LED lamp? Haha… me!
Update 29 May 2017: the third LED light has now failed, so that makes it a 100% failure rate – and it’s the same problem as documented in this article.
The Symptom
The power pack is supposed to output 13 V DC. On the faulty power pack, there was no voltage output at all.
Opening the Power Pack
There are no screws holding the two halves together; they are plastic welded. You literally have to crack it open.
I used a chisel and, by gently tapping and levering, was able to crack it open pretty cleanly along the midline.
Finding the Problem
This is an SMPS (switched-mode power supply), so there are live and dangerous voltages inside that can kill you. Don’t disassemble it until you’ve let it sit idle for at least 5 minutes after unplugging – this gives the high-voltage capacitor time to self-discharge.
Typical vulnerable components on SMPS units are diodes and output transistors / MOSFETs. I went straight to the output diode and, lo and behold, it was shorted. With the DMM in diode mode, a healthy Schottky diode should show around 0.3 V; this one showed 0.001 V.
This Schottky diode SR1100 is rated at 1 A, 100 V. I ordered some SR2100 (rated at 2 A) from AliExpress – about $1 for 20 – more than enough to repair these multiple times!
Schematic and Other Suspect Parts
Apart from the Schottky diode D7, another component that is susceptible in my opinion is transistor Q1.
One word of warning: when replacing any components on an SMPS, make sure you are replacing them with the same type and rating. Capacitors are not just “capacitors” – different types are used for different purposes.
For example, it is critical that CY1 is replaced with the same type. It is designed to fail open (although nothing is guaranteed!) instead of short. If it fails short, there can be dangerous live voltage on the output.
Remember those stories of people being electrocuted using non-genuine phone chargers? Same idea – so pay attention to safety parts!
Putting It Back Together
Once the diode was replaced and everything checked over, I used super glue to glue the two halves of the power pack together.
Back on the bench, the lamp worked again and went straight back into service clamped onto my trusty microscope.
Power Consumption
This lamp uses about 0.5 W on standby and around 7 W when operating. Its standby consumption is OK, but not the best. Given that it is a low-cost (did someone say Aldi!) item, it’s acceptable.