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Alan Rencher

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Everything posted by Alan Rencher

  1. You need to find the wattage of each device along with the maximum constant drain rating of your battery. Those specs should be in the manuals for your respective devices.
  2. If you email or call Preston, they will be glad to give you all the info you need. It's better than getting it second hand.
  3. Just a note, these photos are of Alan Kelly's sled, and they were also taken by him.
  4. Again, Jess, it's not a problem with the shared ground. The problem is when you are using the positive terminal on the first battery without filtering out the ground from the second battery. If you do that, and the two system's respective positive lines come in contact, even when regulated, the floating ground from the second battery will short with the power coming from the 24V line.
  5. If you look at how series wiring works, you will see that no matter if you derive 12V from the first or second battery, you will be connecting to both a positive and negative terminal. A rectifier should filter out the problem. I don't know why you're arguing with me. It's like you trying to Fletcher me, or something. What I am talking about is specifically the P-Tap in the CineLive. The short that is happening in the video is exactly what I described in my post; there is no questioning that.
  6. The Intersex Plate and Monster Hands also work very well with the Blackmagic Video Assist. http://mediablackout.net/collections/intersex-plate-kit
  7. Jess, As you can see in the video that Will and Brian posted, it can happen with certain rigs. Using anecdotal evidence as a blanket argument is not in the best interest for people who have experienced this problem. The SDI line doesn't send 12V or 24V, but rather a much lower voltage; if you have a floating ground in one of the positive lines, you'll cause a short when it meets the positive from its source battery. That is what's happening in that video.
  8. Just a quick note about the DJI follow focus - it has no remote start feature; that is, you cannot remotely start/stop a camera with the handset.
  9. That's incorrect. The problem is not from the shared ground. It comes from the positive lines. I'll do a video follow up when I have time. A bridge rectifier on the 12V line would probably fix the problem.
  10. Check out the rundown of the I/O on the new Varicam LT on the Media Blackout Blog: http://mediablackout.net/blogs/news/92206214-what-you-will-need-for-your-new-panasonic-varicam-lt
  11. This is a more common problem than you might think. Any sled that has a switch that puts the battery plates from parallel (12V) into series (24V), but doesn't either use a regulator or use an isolated third battery to output to the 12V line has a chance of causing a short through coaxial lines. Here's the basic principle: When you have a sled in parallel mode, all positives and grounds are tied together, respectively. This doubles the power capacity while keeping the voltage the same. When the system is switched to series, the positive of one battery is connected to the ground of another battery, just like when you stack AA batteries in your remote control. This doubles the voltage while keeping the power capacity the same. Here's where that bit about needing a regulator or an isolated third battery comes in. When you have a system that is wired in series, the proper way to get 12V is to take the 24V from both batteries, and step it down to 12V with a regulator OR, you need to use a third battery that isn't part of the series. The sleds that are creating shorts in 24V are actually creating the short with how they achieve 12V. These sleds achieve simultaneous 12V and 24V by connecting to the positive and negative of just one battery in the series. This won't cause a problem if you are isolating the 12V and 24V devices, but if you tie the two systems together (like through a BNC cable), you are actually shorting the positive of the 24V system with the ground of the 12V system. There's an easy way to test this with a multimeter: First, take the negative probe from your multimeter and find the ground pin on your 3-pin 12/24V output on your sled Second, test each positive output with the positive probe of your multimeter. On fully charged cells, you should read ~32V on the 24V line and ~16V on the 12V line. This is normal and fine. Third, find the short! if you place the negative probe on your 12V line and the positive probe on the 24V line, an interesting thing happens, you will read ~16V! The reason this happens is because the positive wire of the 12V line is tied to the positive terminal of the one battery in the series and the positive wire in the 24V line is tied to the positive terminal of the other battery in the series. BUT if you pay attention to how series wiring works, the positive wire of the 12V line is ALSO tied to the ground terminal of the second battery in the series. Therefore, just as you did with your multimeter probes in the test I described. when you connect a BNC line from the camera being powered from the 24V line to the device being powered from the 12V line, you are shorting the second battery in the series directly to its own ground terminal. The tricky part with coaxial lines (both coaxial power and coaxial video) is that they are not usually isolated from chassis ground. This is where a short can travel through the whole system, even if you think two systems are not connected together. This is also a problem with having working P-Tap ports on battery plates in a system that can switch to series wiring.
  12. I posted this in the wrong thread. I moved here to the correct one here: http://www.steadicamforum.com/index.php?showtopic=23257&p=115877
  13. $7,000 OBO I'm selling my lightly used Paralinx Tomahawk SDI 1:1 kit. Kit is on mint condition and includes: Paralinx Tomahawk SDI transmitter Paralinx Tomahawk SDI receiver Paralinx Perch mounting bracket for receiver Anton/Bauer power pass-through plate for receiver Paralinx Sidearm mounting bracket for transmitter Standard antennas AC adapter Arri 2-pin power cable P-Tap power cable Hard case I will be considering reasonable offers. The value of this kit purchased new directly from Paralinx is over $8,150.
  14. Hey Michael. Will you be doing tests that involve short circuits, introducing 24V inline, pulling max discharge for long periods, pulling more than the max discharge rate, etc?
  15. I'm designing a director's monitor setup for Bolt Sidekick/SmallHD 702. If anyone is near the Culver City area, and could lend me their kit for a short time, I could hook you up with a prototype at my cost.
  16. Please email enquires to alanjrencher@gmail.com Located in Culver City, CA
  17. Please excuse the stock photo; I will be taking actual photos of the cart when I go to my storage unit tomorrow. This is the Filmtools brand Magliner/Backstage Jr Steadicam Cart. The cart sells new for $1,500, but I'm looking for $1,300. I'll be considering reasonable offers. The cart comes with all you see in the photo including vest holder, mast, handles, shelf, bumper, and bungees to keep it all together. It all folds up for storage. There's normal wear and tear, but it's in pretty great shape. I bought the cart new about four years ago.
  18. This is a well-used and well-cared-for Steadicam Zephyr Kit with: - A/B Battery Mount - Secondary A/B Battery Plate (12/24v) - Standard Vest - 7″ Marshall HD Monitor w/ Sled Cable - Sled (Camera Mounting Chassis) (24 lb capacity) - 2-Section Iso-Elastic Arm (36 lb lift capacity) - X-Y Vernier Stage - Drop-in Dovetail Camera Mount - 2x Lemo Power Connector on Stage - 2x BNC Connector on Stage (composite and HD) - 2-Section CF Post - Dual Rod Base - Docking Bracket - Low-Mode Bracket - Hard Case I can also make any cables you may need to go with this kit at an additional cost. Shipping will be the responsibility of the buyer, and it is also available for pickup in Mid-City LA. I'm selling the kit because I'm focusing on my other business for the time being, and these funds are better suited elsewhere.
  19. New: Alexa Mini Audio Cables Media Blackout’s Alexa Mini Audio Cables plug directly into the Alexa Mini’s 5-pin 00 Series Lemo jack on the camera body to allow direct connection to microphones, lav packs, and other audio equipment. All Media Blackout audio cables are properly shielded; don’t be fooled by other manufacturers’ “Flex” cables that are just bare hook-up wire in nylon sheathing. All styles of Media Blackout’s audio cable for the Alexa Mini are flexible enough to use with gimbal rigs. http://mediablackout.net/product/alexa-mini-audio-cables/
  20. Heden Engineering remote start cables have been added to the store: http://mediablackout.net/product/heden-remote-start-cables/
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