Alexa Mini / Preston V+F Issues - Blown Control Unit
Posted 27 February 2018 - 06:15 PM
Posted 02 March 2018 - 01:47 AM
Well the voltage input to a Mini is directly passed out the EXT socket, so any input spike would be passed on to the Preston. (Standard Alexas regulate input voltages under 24V up to 24V for their RS sockets, but any voltage input that is above 24V is also simply passed through, so be careful powering accessories that are sensitive to over-voltage if your block battery is 30V for example).
But as far as I'm aware a battery plate like the Wooden Camera ones we use with Minis should take whatever the highest voltage is and pass it to the camera, until both sources are at parity and will both get used. Disconnecting one input source might cause a voltage drop, but not a voltage spike.
Also, Prestons can take a wide voltage input, something like 12-28V from memory, so should normally be fine with whatever is powering the camera.
However Preston did issue a bulletin last year about the dangers of using split-level power supplies, meaning having power grounds at different potentials. This can be caused by powering accessories from a separate power supply to the camera for example, or sometimes by faulty cables. To diagnose something like that you'd need to measure the GND connections of your system setup with a voltmeter to make sure there were no voltage differences. I don't know if that was the cause of your issue, but it seems safe to say you didn't do anything out of the ordinary, and the rental house might need to investigate further.
Posted 03 March 2018 - 12:40 PM
Thanks Dom, very interesting about the split level power supply warning and seems like a very plausible explaination. Do you have the full text of that bulletin? I can't find it on their site and the only other place with it seems to be the Steadicam forum where I'm waiting for my user registration to be approved.
Posted 03 March 2018 - 07:06 PM