This IS the Avid L2: Re: [Avid-L2] Destorted Reference Signal Causing Avid to glitch? [2 Attachments]

Saturday, April 12, 2014

Re: [Avid-L2] Destorted Reference Signal Causing Avid to glitch? [2 Attachments]

So I've ordered a video humbucker to see if that will knock down the hum so Avid doesn't react to it's intermittent presence. I'm going to see If I can attach the 2 field display on the Tek 1750 display showing normal and hum. It's unterminated so it's twice the level it should be on the scope but that makes the hum more apparent.

---In Avid-L2@yahoogroups.com, <Greg@...> wrote :

We actually have had a similar problem, but it was tracked down to a AJA DA that was burping. I think it was actually overheating - kinda crammed into a 'quiet box,' sitting on top of another piece of gear. As a test, I kinda 'hung it in mid-air' off one of its cables. Bad form, I know, but it works, and the glitches have stopped. I'm not suggesting that strategy, I'm just saying that stuff happens...

gh
----------------------------------------------------
Greg Huson
Secret Headquarters, Inc
Post Production / Production
Culver City, CA
323 677 2092
www.DigitalServiceStation.com
greg (at) SecretHQ.com
www.SecretHQ.com

On Apr 3, 2014, at 5:10 PM, John Moore <bigfish@...> wrote:

>
> For several months I've been chasing what I first thought was a tape deck error but know have come to realize that the error is coming out of my Avid Nitris Bob when I'm set to external reference. Our plant has a gen 10 set to ntsc black on 4 ouputs and 2 for 23.98Psf. The first output feeds a 1x50 DA that distributes sync to bays and decks. What happens is that the Avid output just glitches just like if you disconnect the reference signal and then plug it back in. Every time I remove the sync when I patch it back in the output from the Avid glitches two time separated by approx a second. I have bypassed the sync da and run a direct out from the gen 10 output 2 to a different tie line to my bay which is approx 50 feet from the machine room. I still get the glitches every so often. Also it seems like the glitches occur in spurts at various times during the day. These glitches are catastrophic to an HDCam or SR tape output. They put a glitch on the tape that can only be eliminated by assemble editing from that point on.
>
> Today I brought my tek 1750 composite scope in and I've looped the ref signal through it before going to my Avid. If I look at the black signal in field mode it looks pretty good but every so often the flat lines pop with a sine wave signal that when looking at a 2 field view looks like it makes a cycle about the duration of each field. Which makes me think it's some sort of 60 cycle hum ground loopy thing that intermittently pops in. After popping in it pops back out in about 5 to 10 seconds. At the point of the pop out of the hum the avid output glitches approximately a second later. Our facility has a 60 cycle hum ground loop that I've seen before but it was more of a constant distortion not this popping in and out. It's only been the last 3 to 4 months that I've seen the Avid output glitch. I'm wondering if some AC unit or similar is somehow sending something whacky through the power when it kicks in or out. Anybody have any ground loopy noisy power trouble shooting suggestions. We are not running isolated grounds in the bays and I'm not sure how the machine room was. We have added a second unity about the time these things started happening to me. Perhaps there is now an excessive draw in the machine room that could cause temporary low voltages when enough cooling fans kick in. I know it's a nebulous thing when dealing with these hum/ground loop oddities but does anybody know how much power demand swings on unities and we have a san mp as well. Whatever is causing this it comes in flurries at various times of the day.
>
> Has anybody in their spare time run in low power tests to an aja gen 10? I don't have access to my old high school electronics lab where we had a box that you could dial down the voltage. Oh well it's always got to be something and now I have that syncing feeling. ;-)
>
> John Moore
> Barking Trout Productions
> Studio City, CA
> bigfish@...
>
>