Film-Tech Forum ARCHIVE: DA-20 issues

This is topic DA-20 issues in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=009802

Posted by Jeff Else (Member # 4063) on 03-14-2009, 08:25 PM:

I have a DA20 with a BACP DTSR-20 reader connected to a Smart mod V exhibiting the following behavior... The DA20 reads a reasonable error rate.. 3-4, or 4-5 depending on the print quality, but intermittently fails for just a split second, causing audible glitches, but not switching the processor back to analog. Our tech suggested a new LED for the reader, which I replaced. The error rates seem to be lower between failures, but the failures persist. To add to the DA20's odd behavior, it has trouble sometimes initially switching the Smart to digital at the beginning of the show, and then inexplicably switches the smart back to stereo at the end of show after the automation switches the smart to non-sync. (I know its the DA20 because if the DA-20 is off, the end-of-show sequence runs fine.) Also same film in another auditorium will run fine at the end-of-run, so its not a cue placement issue. What's wrong with my DA20??

Posted by Gordon McLeod (Member # 33) on 03-15-2009, 08:14 AM:

The probelem is that the smart doesn't provide any format sense information to the DA20

Posted by Marco Giustini (Member # 4544) on 03-15-2009, 08:40 AM:

Repeated and fast "F" in my experience are due to quick variations in film speed. I had a cat 700 where you could see the dumper moving up and down quickly. Error rate was 3.5/F/3.5/F without swithing to SR.

On another projector the sound drum shaft was bent. Same issue.
On WinDRAS you can check the Vertical Jitter value.

Unfortunately I know nothing about BACP. I suggest you to check everything that can lead to speed instability.

Marco

Posted by Demetris Thoupis (Member # 833) on 03-15-2009, 09:46 AM:

The BACP Digital reader is actually good or even better than most of Dolbys' units. Have you checked the readers' allingment perhaps it fell out of place? The video level is it at 4V or is it lower or higher? There are two guide lines at the threading path of the the BACP unit. Make sure when you thread the pad rollers are at the guide lines and not lower or above for that will cause uneven balance to your film. The last thing I would suggest is change the Video Aquisition board of your DA 20 (I think is Cat 670 but not seeing a manual right now) with another DA20 if you have and see how it goes.
Demetris

Posted by Jim Cassedy (Member # 4115) on 03-15-2009, 09:51 AM:

In my experience, the BACP readers are excellent pieces
of equipement and are pretty forgiving of minor film
glitches and speed variations that would cause the
older Dolby readers to gag, or at least hiccup.

Posted by Mark Gulbrandsen (Member # 72) on 03-15-2009, 10:37 AM:

First by using at least a 60mhz bandwidth scope verify that the incomming video is good from the reader. After verifying that it's good and if you have a second DA-20 swap the cards between units one by one until you've pinpointed the problem and then relace that bad card. Beyond that all I can say is that I've had just about every card fail in DA-20's over the many yers they've been out. An intermittent on at least severl of the cards in there could cause your issue. You may also want to call Dolby Tech Support and see if they have this problem or a similar one on file from another incident. If they do then it'll make it easier and far less expensive to repair your unit.

Now... If the problem's in the Smart you can't reliably call Smart any longer since they vaporized nor can you really get any R/A parts for the Mod... a good case for only buying Dolby products(USL BTW is also very good at product support longevity)! No other companies are on my short list to buy sound processors from any longer.

Mark

Posted by Michael Schaffer (Member # 1204) on 03-15-2009, 09:48 PM:

The problem is probably in the Cat.No.611 card. It would be good to check if it is 611 or 611A and if the former, upgrade to the latter.