grant mcphee Posted November 13, 2007 Share Posted November 13, 2007 Hello, I was video assist on a commercial recently and encountered a strange problem that I couldn't/can't figure out. We were using a 435 with a pal video assist, 21" monitor for client and 9" dvcam combi to record. A fairly standard package for low budget commercials and something I'm pretty familiar with. At the start of the day I connected everything up - Camera to DV Combi and daisy chained DV Combi to Client monitor using the video out. I used a 50' cable drum for each monitor with a 5' short bnc to connect. Camera was switched on and each monitor had a picture. Nothing odd, I'd done this hundreds of times before. The focus puller was having a problem with the frame markings. He'd not used the 435 for a while so until he worked out how to sort it he asked if he could t-piece out of my bnc (he was using the one with the info, I was using the clean one). He was using the transvideo 5" so I quickly t-pieced up his monitor out of the other bnc. He got the image, as expected. I quickly checked the dvcombi which also had a picture. As the client monitor was daisy chained from this I did not check it - it was working fine before. A couple of minutes later I got a shout that the client monitor had gone down. As the only new piece of equipment used was the t-piece and on board monitor I tried changing that t-piece with no luck. I quickly tried changing the bnc to the client monitor - still no picture. We decided to switch the on board monitor back to it's own bnc as it had been at the start of the day - everything worked again. we decided to keep this set-up as there was not enough time to find out what was happening - i assumed it would be something to do with the dvcam, possibly some kind of resistance issue - though I always thought that it's output was amplified. Termination problems usually still give a picture. Later on the dop asked if he could have a monitor for himself. I daisychained this into the start - camera, 9" monitor, dvcam, client monitor. As before, the client monitor had no picture. I tried a few variations - t-piecing the output of the camera so the 9" had a seperate bnc - I would have expected the client monitor not to have a picture but on top of that the dvcam combi did not have one either. It seemed to be something with the video assist. Swapping the output of the t-piece over had no effect (always a picture to the 9"). In the end I t-pieced the output of the onboard to the 9" and kept the dvcam/client with it's own output - though not great for the grip having two bnc's trailing out of the camera. Any ideas? I'm not an engineer so don't have a great knowledge of what's going on inside. But like I mentioned, I've done this plenty times without anything like this happening. Am I doing something odd and have just been getting away with it? I don't think it's a termination problem as the sony monitors are auto terminating, and at some point I did try using external terminators in case the internal sony ones had packed up. It does suggest a resistance problem as the monitor which is furthest away is the one having the problem. Is it the output of the camera? On the other hand, I've used a 435 with well over 200' of bnc and had no problems. Any suggestions appreciated. I might be using the same camera again on a more complicated set-up so wan't to know if it's something I should get the rental house to look over. thanks Link to comment Share on other sites More sharing options...
Premium Member Hal Smith Posted November 13, 2007 Premium Member Share Posted November 13, 2007 I was video assist on a commercial recently and encountered a strange problem that I couldn't/can't figure out. A quick thought (I'm out the door to a gig). It sounds like you might have had more than one termination. You need one term at the end of the daisy chain. If you bridge a monitor off with a tee make certain the added monitor is non-terminated - it should be in bridge mode. If I had to guess, the Sony monitor autotermination is creating the problem. Can you turn it off and use a 75 ohm bnc terminator instead? Link to comment Share on other sites More sharing options...
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