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Trouble jamming Alexa with Ambient ACL 204


Saif and Sound

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So i have an Ambient ACL 204 Lockit box and I will be on a shoot with the Alexa next month.  I know the Alexa has a pretty easy work flow regarding timecode and I have jammed it plenty of time in the past with other models of lockit boxes.  But every time i use my lockit this is what happens:

 

This is of course assuming the Camera TC settings are set to...

Source: EXT LTC

Mode: Free Run

Generator: Jam Sync

User bit source: LTC in UB

 

1. I jam the lockit box from my recorder...the time code matches perfectly.

 

2. I use the lemo to lemo cable out of B lemo in/output. (the one closest to the BNC)

 

3. I plug the other end into the Alexa

 

4.  Instead of the lockit box jamming the Alexa, the opposite happens and the Alexa jams the lockit box and the timecode changes back to 0 and counts up from there.

 

Any idea why this is happening?  I feel like i remember reading somewhere that it may have to do with the cable being a two way cable or something but I'm not too sure. I havnt had any time to do a camera test and hammer out the kinks.  Anyone else have this issue?  Any advice would be appreciated. Thanks!

 

   

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You probably are using a 2 way cable. One fix is get a one way cable so that the timecode doesn't send to the ACL204 from the camera. You can also go into the menu settings on the 204 and change the Jam on the unit. It is set on AUTO and you can change it to Manual/Once. Go into the Menu and go to Gen. It is in that Menu item.

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You probably are using a 2 way cable. One fix is get a one way cable so that the timecode doesn't send to the ACL204 from the camera. You can also go into the menu settings on the 204 and change the Jam on the unit. It is set on AUTO and you can change it to Manual/Once. Go into the Menu and go to Gen. It is in that Menu item.

 

Dear Saif,

Ryan is completely right. Please remember that if you like the Alexa to be continously synced by the ACL204 to set the camera into EXT-TC/Regenerate mode. If you just want to jam the cam once the Jam mode would be right. Even if you could avoid this error by setting the ACL204 into jam once mode I still deeply recomment to use the bidirectional cables ONLY to tune Clockit or Clockit integrated devices... By setting the ACL204 to jam once you can't rejam it after lunch if you leave it running... ;)

 

Timo

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I recently worked (for the first time) with an Alexa as well and solved the time code issue I was having by renting a Denecke SB-T box and cables from Trew. I was using the 744t as the Master and the camera was slave. However, now I think I didn't need the box since I only had one camera and my bag was portable.

 

Could I not have simply walked over to the camera with the proper lemo to lemo cable and jammed synced the time code without the Denecke? If so, would a two-way cable work or would I have to use a one-way?

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Yes, with the Alexa this is possible to a certain point. And for that you definitely would need a one way cable.

 

The problem with this workflow is always that you've got two digital systems where the processors are running on different speeds. How different they are is depending on the modell, the firmware version, the weather, the day they were assembled, the guy who assembled it... With other words you just don't know. You definitely need to test it carefully.

The Alexa is one of the best clocked cameras out there and still we got 6 frames drift in only two hours ( thanks to a bad firmware revision). So if you don't want to think about all this stuff and if you want to be sure that your setup works even when it gets 10 degree celsius hotter (thanks to lights,...) you still should use a sync box.

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P.S. If you tune the Alexa and your 744t with an ACC 501 the drift will be about 1ppm. Which would be good enough to work  without a sync box for approximately 3 hours maybe even more.

Since the Alexa loses the tune value when she is without power for more than about 5 minutes you would need to retune it every time it could have lost the value. So this solution is in my opinion not as comfortable, more expensive and less safe. Thus this workflow is mostly used when the camera guy convinces the production that he can't work with such a thing on his machine. ;)

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Dear Saif,

Ryan is completely right. Please remember that if you like the Alexa to be continously synced by the ACL204 to set the camera into EXT-TC/Regenerate mode. If you just want to jam the cam once the Jam mode would be right. Even if you could avoid this error by setting the ACL204 into jam once mode I still deeply recomment to use the bidirectional cables ONLY to tune Clockit or Clockit integrated devices... By setting the ACL204 to jam once you can't rejam it after lunch if you leave it running... ;)

Timo

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