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troubleshooting a weird 2.5K Strand (IREM) HMI ballast
Alain Bourassa posted a topic in LightingHi guys Looking for new ideas here , I'm an electronic technician with 25+ years of experience , working with HMI since the mid 90's I also work as a DIT and Engineer I was on a set last weekend, shooting outside on a very humid day one 2.5K HMI Par was outside and the ballast did a flash and me and the DP heard a sparking sound when it happened the light stayed on but once we turned it down it never responded to the ballast later on the lamp is an old Strand Quartzcolor and the ballast is a magnetic ballast , Strand brand , made by IREM (same guts as the ARRIs) My first guess was a blown capacitor inside so yesterday back in my workshop I opened it , replaced the 2 main electrolytic capacitor on the IREM pcboard and the main power cord too which was very brittle, I used gauge 12 wires as usual tried the ballast with the head we had on set, it strikes and after a few minutes I see a lot of flickering and I'm hearing a loud hum from the ballast, like a AC to DC rectifier only working on half the phases tried the ballast with a second head it strikes but does not stay on but the lamp works well with my other 2 ballasts of the same model tried the same ballast one more time with a third head it strikes, light goes on and no hum no flicker ! like a perfect combo I used the same cable on the 3 heads too so the cable is discarded as a possible problem source I have never seen such a stubborn ballast in my life