Switch is easy to check with cooper wire to bypassing it .
Electronics heat up and work , problem is some fault component , but real problem is electronic encapsulation to get it.
We have in lab 3D X ray scanning machine like
phoenix v|tome|x s CT 3D Metrology X-ray Scanner | Inspection & NDT
I see sometimes problems ( our company made drives for power BLCD motors ) when potting compound destroys electronics components
( electronic and compound have different thermal properties than PCB and old components TH (through hole) work without problems , but small SMD( surface mounted ) might be in bad soldering joint and heating up potting compound and evade or short soldering pads (special very small SMD )
HID is out , special in small portable lights , bulbs , ballast are expensive and hard to get … waste of money and time
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PS: could be very interesting update your old HID to modern led using and is DIY friendly
Philips H7 Ultinon LED 6000K
LMGTFY ( leds must be small and powerful and in same position as HID meniscus )
instead of standard test tube you need open tube and cool down led in front of light instead of back of the light with Alu metal plug. You only have to solder two thin cca 0,75 - 1,00 mm ''magnet wire'' back to ballast cavity to led driver …( you get that in kit) ….
sketch is old study - i think that is very clean and working solution
i want to made this once but , now I don't have body anymore and other lights work ;-)