my profile | my password | search | faq & rules | forum home

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » Dolby Cat 701 Question

Author Topic: Dolby Cat 701 Question Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 06-28-2005 08:17 PM                     We may have gone through this before, but does the LED go dim over time to the point where it needs to be changed. I have one at one theater that has been in use for six years. It is always kept on. Now all the movies that run, even the new prints, will not hold better than 7 or 8 on the error readout. Also bounces back to F to the point where it will not play digital. It does the same thing with brand new test film. I did not have the scope with me at the time to check it out.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 06-28-2005 08:28 PM                        1. Yes, the LED slowly fades out. 2. Dirt, smudges on lens and LED may be a factor. 3. Anything mechanical that causes wow/flutter, bad sprocket will cause faults. LED most likely due to time involved. (If possible, power the 701 off of the motor circuit so it does not run except during the actual show.) Louis  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 06-28-2005 09:07 PM                     Thanks Louis, I did clean the lens and led. I ran new film to test with. Everything ran smoothly.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 06-29-2005 07:40 PM                     Richard, The LED current can be adjusted inside of the 701 to compensate for LED fade. If this has been running a long time then having it tweeked for correct video level is a good idea. I can guarantee you that video level will be low! Cleaning the lens and optics may get you by and gain you just enough extra video level to be able to decode, but not for long. I had a customer that had turned his voltage level up too high for what ever dum reason and this also caused the input opf the Video card to bury the datalevel into the pedestal causing a constant F reading. The adjustment is simple but a scope is necessary for this!! Mark  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 06-29-2005 09:11 PM                     Thanks Mark. I thought there might be voltage adjustment. I'll bring the scope and try it.  |  IP: Logged Ken Jacquart Film Handler Posts: 82 From: San Francisco, CA, USA Registered: Mar 2000 posted 06-30-2005 11:56 AM                        Additionally, if you ever replace the LED, remember to turn the current back down in order to preserve it's life expectancy. Incidentally, you can RXO the LED / heat sink assembly. It is Dolby part number 83308. If it has been in service for six years, you are fortunate that it's still produce enough video amplitude.  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 07-11-2005 07:00 AM                     Just a quick note. I raised the LED output level slightly and the error rate dropped from 7 to 3. It plays perfectly now. I will just have to lower the LED level whenever I change the LED. Thanks again everyone.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 07-11-2005 02:43 PM                     Just an FYI in the simplest terminology that I can explain here... Although you probably greatly improved the calibration of that reader by upping the led output to the point where a "7" print is now tracking at a "3", you could've also been running a bit of a "dark" SRD track at the time and as such "lighter" tracks will now F due to having too much light shining through the track. Make sense? Of course if it's been running for 6 years, maxing it out is honestly probably what needs to happen to achieve level as close as possible to ideal.  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 07-11-2005 03:16 PM                     It does make sense, Brad. This has been happening over the last few months with many prints. They just don't tell me things that are going wrong until much later than they should. I did not have to max out the adjustment, either. Just a little bit of gain did the trick.  |  IP: Logged David Graham Rose Expert Film Handler Posts: 187 From: Cambridge, UK Registered: Sep 2002 posted 07-12-2005 03:14 PM                     Greetings to you all Louis is indeed correct. Hello Louis - good to hear from you and hope you are well. We met many years ago at ShoWest! Hope you still have your aeroplane for emergency call outs!! All the projectors that I have ever researched here in Cambridge have been modified to switch on the LED array with the commencement of the motor. I have calculated that one will obtain many additional months life from an LED switched in this manner, unless of course the theatre is running continuos performances, as occurred here in the UK in the '40's and 50's. From Cambridge, Goodnight  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-12-2005 05:43 PM                     quote: Brad Miller Although you probably greatly improved the calibration of that reader by upping the led output to the point where a "7" print is now tracking at a "3", you could've also been running a bit of a "dark" SRD track at the time and as such "lighter" tracks will now F due to having too much light shining through the track. Make sense? Actually what happens is thhe equivelent of having a tv camera iris too far open. You actually overload the video stages at some point in the chain. I'm not sure if it occurs in the camera or on the video input card itself... doesn't matter much though..... you still need a scope to properly set it up. Mark  |  IP: Logged

All times are Central (GMT -6:00)

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.