Chemistry Electronics Services
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Repairing Solar Light's XPS-400 xenon lamp-driver "Solar Simulator"

Our unit will repeatedly ignite the lamp, but it won't "catch." Not a bad lamp: a new xenon lamp behaves the same, repeatedly flashing.

It turns out that this product has a design-flaw in fan cooling: a large slot between the enclosure and the upper edge of the power supply. Cooling air flows directly to the outlet, so that the front of the unit isn't cooled. The capacitors up there overheat and decrease in value, until the 24V supply cannot put out high wattage anymore, and the lamp quenches after ignition.

Note that to take the case apart, the plastic bezels unsnap. Remove only the front panel (first remove the switch knob and its set screws.) On the back, remove the top two screws, then slide the extruded aluminum cover to the front. Note the original alignment of the switch knob and of the LCD display connectors: the upper-right pin and the lower left pin will plug into the far end of each ribbon connector. Perhaps take photos before unplugging!

Right side of the case is taken up by "Deltron V501D04" DC Power Supply, 24VDC 30A 740W, inp 115V 14A. I found that the supply had been overheated, with the two capacitors (1200uF 200V) value decreased by 25%. Also on the two power transistors, the Molex connectors plugged into their pins were discolored, and the transistor pins oxidized. So, in the Molex connectors I remove and replace the KK-156 crimp pins, and clean the transistor pins. Replace the two large capacitors with Nichion LGW series, 1200µF 200V Digikey 493-8523-ND.

The fan airflow design is poor. Much of the airflow is "shorted out," so the front of the unit doesn't cool enough. I added a barrier of duct tape to the rear half of the upper edge of the DC power supply, so air won't divert across the case, and must instead flow to the front.

The three large 2200uF 200V "ignition capacitors" also are aged, with values decreased to 1500uF. However, the unit started working after only replacing the two 1200uF caps in the Deltron supply, so it looks like those were the actual cause of failure.

Note that live 120VAC is present on the rear connector pins to the lamp housing cable! This acts as an interlock: removes AC power from the Deltron 24VDC supply whenever the lamp housing isn't connected.