Old HMI head with new ballast

Arunas Eimulis · August 9, 2018

Hi, is it possible to use old Sirio 4k HMI head and new arri or similar ballast?

Will it be enough just to make an adapter cable?

Edited August 9, 2018 by Arunas Eimulis

Guy Holt · August 10, 2018

It is possible, but may be difficult. You first have to make sure the two have the same style of Veam connector. From the photos it looks like it does not. The head cable uses a 9-pin and the ballast uses a 7-pin. I would recommend a used Power Gems 425CDP (you see them sometimes on ebay) or an older magnetic ballast over the Chinese knock off pictured. If you can find a ballast with the same style veam connector it will save you having to swap it out for the right one. If you can find a ballast with the same style veam connector you have to make sure the connectors are keyed alike - the slot in the rim aligns with the same pin. If it doesn't you can take it apart, file out the plastic shell so that it does. Finally, you have to make sure the "pin out" (what pins serve what function, i.e. VOH is pin 8 etc.) If it is not, you can swap the pins around in the plastic shell. You may need to re-solder a wire if it is presently connected to a large pin, but has to connect to the new ballast with a small pin.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting rental and sales in Boston

Edited August 10, 2018 by Guy Holt

Phil Rhodes · August 10, 2018

The connector in the photo has nine pins. The connector on the ballast has seven, which I would assume is more normal. Am I missing something?

The Chinese ballasts usually work but can be effectively stuck in flicker-free mode, so it'll buzz - basically it's a common off the shelf metal halide ballast, which is fine, but it isn't really built for movie work. Yes, sometimes the mode selection switch is just a rotary switch and some LEDs, which does nothing. Beware.