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This topic comprises 2 pages: 1 2
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Author
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Topic: Optimizing the dolby error rate
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Paul G. Thompson
The Weenie Man
Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000
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posted 08-25-2002 01:42 PM
Josh, look at the tension rollers in the CAT 700 and check to see how stable they are running. Any bounce is too much. Also, check and see if the center roller in your AW-3 pay-out heads have the holdback tension spring installed and working. Those should help to improve the error rate.Lot of people have removed those springs for one reason or another. Pete Naples is right on target with his post.
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Brad Miller
Administrator
Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99
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posted 08-25-2002 01:58 PM
What's the specific goal here? Are you consistently getting high error readings and want to lower them overall, or is there one print that is giving you grief dropping in and out you want to try and get to play? The reader can be calibrated for a specific film, and there have been a couple of times in the past that I did just that to make it play. However do note that re-aligning it for that one film DID and WILL knock it off for all others to play back properly.When aligning I recommend you use an "average" loop from a Deluxe printed trailer. Just make sure you look at a bunch of different loops on the DRAS to find an "average one" of the variables. I've never been pleased after calibrating with actual Dolby loops. Also note that getting readings below 2 on a cat701 is almost impossible. The cat699 and 700 penthouses are easy to align such that 0-1 is a common reading.
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Pete Naples
Phenomenal Film Handler
Posts: 1565
From: Dunfermline, Scotland
Registered: Feb 2001
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posted 08-25-2002 04:49 PM
Brad, it's not almost impossible to get below '2' with a 701!I've got stacks of those in use up here and regularly see '0'. Admittedly these are the newer type with the large diameter lens on the camera. Also I've never touched the alignment of these, they are exactly as they came out of the box.
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Josh Jones
Redhat
Posts: 1207
From: Plano, TX
Registered: Apr 2000
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posted 08-26-2002 12:21 AM
I was just looking for generic troubleshooting should the need arrise to calibrate the reader. We've got a cat 700 at work and on "The emperor's new clothes, saw the error rate drop to 1 for a brief second, the best reading I've seen here. throughout that reel it was holding constant 2's.Brad, When you said you calibrated the system for a particular film, what exactly did you do to the unit to calibrate it. Josh
It is indeed a sad day, the last day of summer. School begins Monday at 8:25 am <shudder>
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Martin Dean
Film Handler
Posts: 11
From: Duluth, MN, USA
Registered: Aug 2002
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posted 08-27-2002 09:44 AM
If you are using an older penthouse reader, pre LED you may also want to check the bulb. As the bulb degrades the error rates will increase. Put a new bulb in and you usually find the error rate improves back to where it should be.Also if you are running a component engineering basement reader on a Westar or Century you may be having problems with vertical jitter. The problem appears as intermittent 'Fails' of the digital, a poorer error rat and can lead to they system timing out of digital on a regular basis. Endless time can be spent trying to track down the cause (which has may have no other visible effect), or you can do a small mod to help stabalise the top damper arm. This requires hooking a second spring from the top of the exisitng spring down onto the fixed part of the reverse scan assembly between the two tension arms. This will require drilling a small hole and inserting a small self-tapping screw to act as a fixing stud for the lower end of the spring. The spring used should be very similar to the one already fitted. If in doubt try a few springs and shorten them if more tension is required. If you go to tight there will be an effect on the analogue, as you will introduce some wow and flutter. This mod vastly improves the stability of the digital and has no apparent affect on the analogue. I have carried out this mod on quite a few 'problem' machines and every time it has cured the problem. It can also improve wow and flutter effects on both digital and analogue. Care should be taken if you want to do this mod as you will create swarf as you drill the hole. The very early version of this mod used a rubber band wrapped around the head as a temporary measure, but the spring is a more permamanet version. The vertical jitted seems to be more prevalent on this type of sound head due to the lack of film that is wraped around the sound drum. This mod is not official. We recieved all sorts of advice about changing sound drum bearings and the compression springs in the sound drum assembley, as well as adjsting the tension of the sound drum compression spring (this can make a small improvement). But the mod described above was apparently the ultimate cure. ------------------
Martin Dean martinidean@charter.net
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