Fix your flickering lamps without a new switch!

The Ikea Jansjö is my favorite desk work lamp. Some of the older ones have problems where they start flickering or stop working entirely. This is often due to bad IDC contacts in the switch. Several tutorials suggest replacing the switch as a fix, claiming the switch is not openable. Not true, you can open the switch with the right tools.

The problem appears to be mainly on the old switch design with curved sides (bottom), not the newer design (top):

Instrutions

1. Open the switch

Use a pair of external snap ring pliers to open the switch. Insert them into the wire entry port and squeeze, being careful not to pinch the wire. Open one side by about 1cm, then switch to the other size to fully open the swtich. Beware of the two clear plastic strain relief pieces that may pop out from each wire entry port.

2. Prepare the wires

Carefully pull the wires out of the IDC contacts. Use a small screwdriver to hold the metal contacts down if needed to avoid pulling them out of the plastic. Strip the wires starting at the position where the contacts bit through the insulation.

3. Solder the wires in place

Use a small tip soldering iron. Place the stripped wire back in the IDC contact. You may need to push the contact open to allow it to fit.

4. (Optional) apply contact protectant

Poly phenyl ether (PPE) is a super slow evaporating oil often used to protect contacts. It’s claimed to stay on for up to 40 years. This is easiest applied with a PPE-containing contact cleaner. One such product is MG Chemicals Super Contact Cleaner with PPE. Applying this may extend the life of the switch.

5. Cut off broken locking pins

The case is held together with friction fit pins, some of which may break off while opening the switch. Cut off any protruding nubs that are stuck on the ends of the top portion of the switch. A broken off nub is shown between the jaws of the cutter.

6. Close the switch

Place the wires back into the switch, then put the clear plastic strain reliefs back in. Place the switch on a solid table, place one palm of each hand on each side of the switch, and press down. You’ll have to push down very hard, don’t worry about the switch breaking. You may need to put all your weight into it. You may need to use pliers if you can’t push it down hard enough. Protect the switch with a cloth for example if using pliers.

7. Do what UL should have done

This POS switch doesn’t deserve UL approval, so remedy that with a Sharpie.

8. Enjoy flicker-free light!

This is a Strong model 62-80005 Xenon short arc lamp ballast, out of the now demolished Station Square cinemas at Metrotown. This drove lamps up to 2.5kW for the small auditoriums in the cinema. The large auditoriums ran up to 6kW lamps.

Here’s the User manual

Ratings are
200-240V 1-3 phase 20.2A input
20-30VDC 50-100A output

We were greeted with the lamp current control pot jammed in the output junction box by the installers.

This ballast dates from 1998, and appears to be an older design. As expected, it’s built very well, with the entire chassis being aluminum.

In the above photo, 3-phase input connections are on the top right, bus capacitor precharge contactor top middle, DC output top left. On the bottom right is the EMI filter and main bus capacitor (6800uF 350V), and the bottom left contains the actual switching power supply unit.

Close up of the contactor and 240-120V transformer used to run auxiliary systems in the projector. Also contains the three 5ohm 50W bus precharge resistors, which the contactor shorts out once the bus cap is charged. This avoids blowing the input breaker when turning on the power and charging up the capacitor.

EMI filter, DC bus cap and input rectifier. Bus cap bleeder resistor also visible on the left.

DC Output terminals

Switching power supply

Schematic from manual. It’s basically two separate paralleled full bridge converters with full wave centertapped output rectification.

Control section has a very “organic” layout, the designer must have really been cramming to get everything to fit.

The output current sensor is clever, just a standard ferrite core with a hall sensor stuck in the core gap. Probably much cheaper than the commercial versions of these sensors, especially at this current rating.