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Author Topic: Dolby digital reader needing adjustment?
Garry Knapp
Film Handler

Posts: 50
From: Mississauga Ontario Canada
Registered: Oct 2016


 - posted 03-11-2018 03:00 AM      Profile for Garry Knapp   Author's Homepage   Email Garry Knapp   Send New Private Message       Edit/Delete Post 
Hi Guys. My dolby audio sounds great. I run a DA20. One problem i'm having is, the output signal strength is sometimes not very good. I really notice this when running reels of trailers. My signal strength number is usually around 6-7. Some get really good, around 4-5. Apart from cleanliness, Are there any simple things I should look at to enhance the strength?

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Marco Giustini
Film God

Posts: 2713
From: Reading, UK
Registered: Nov 2007


 - posted 03-11-2018 04:56 AM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
Hi,

The number is called the error rate. If some of your content reads 4, then your head is probably ok. There is nothing you can do without using an oscilloscope and test loops.

Unless you have a CP650 sound processor? You can check the video amplitude with that and adjust the voltage.

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99


 - posted 03-11-2018 06:08 AM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
The error rate display on a Dolby Digital is a golf score. The lower the better.

6 or 7 is bad. If it goes any higher than 7, the display will read "F" and your Dolby Digital processor will revert back to analog sound.

4 or 5 is decent but, if you have somebody who knows how to tune a Dolby reader, you should be able to get it lower than that.

With a good, clean print and a well tuned reader you should be able to get 3 or better.

A couple of tricks you can do to make sure that your error number is as low as it can go without the need for a tune-up is to make sure the reader is threaded with the right amount of tension.

Set the tension arms so that they just line up with the white marks on the back wall/plate of the reader.

Also, you can apply just a smidgeon of back tension on the film.

Once you've done the basics... keep it clean and in proper working order... you've done just about all that you can do without an oscilloscope and/or special tools and software.

However, I might suggest that you have somebody check the LED in your reader. As they age they tend to get weak. Replacing a weak LED will help you get that error number down as low as possible.

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Mark J. Marshall
Film God

Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002


 - posted 03-11-2018 07:18 AM      Profile for Mark J. Marshall     Send New Private Message       Edit/Delete Post 
I haven't touched a Dolby reader in years, but for what it's worth it was not uncommon for ours to run 0s and 1s.

Make sure your film is clean too, not just the reader. Use Film Guard if you're not already. It helps.

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Carsten Kurz
Film God

Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 03-11-2018 08:13 AM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Most private users will not have access to lab-fresh prints, so it is pretty common to not have low numbers with the typical privately owned feature and trailer prints.

If you have used prints that reach 3-4, I guess everything is okay. Dig up the reader installation manual from the warehouse and read through it. What type of reader is it? Some use LEDs, the older ones tungsten lamps.

- Carsten

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 03-11-2018 11:23 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
Is yours a basement vic 5 reader as i find them the hardest to get good results with

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99


 - posted 03-11-2018 11:27 AM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
quote: Mark J. Marshall
I haven't touched a Dolby reader in years, but for what it's worth it was not uncommon for ours to run 0s and 1s.
Yeah, I would start getting phone calls and e-mails when the Dolbys at my theaters (that I was responsible for) started getting in the 5/6 range.

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Victor Liorentas
Jedi Master Film Handler

Posts: 800
From: london ontario canada
Registered: May 2009


 - posted 03-11-2018 12:55 PM      Profile for Victor Liorentas   Email Victor Liorentas   Send New Private Message       Edit/Delete Post 
On a cat700 white light reader,after a few years of not being used much,I believe the lamps reflective coating can deteriorate causing 6 7 f. That's what I'm getting lately. I've bought some new lamps but not had a chance to install one and compare the error rate.
I hope that's all it is. Any advice on carefully cleaning the light pipe surface? Without damaging it?

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99


 - posted 03-11-2018 01:07 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
quote: Victor Liorentas
On a cat700 white light reader,after a few years of not being used much,I believe the lamps reflective coating can deteriorate
The coating typically just clouds up and it is easily cleaned with a cotton swab and lens cleaner. I have never seen a lamp of that type in a Cat 700 or other piece of equipment where the coating is damaged. In my experience the two best penthouse readers are the Cat 700 and the BACP.

If you have a Cat 701/702 then the video level may be low and in need of adjustment from the normal fade rate of the Red LED. Also check the lateral guide roller to see how worn it is. It's the upper roller (I believe) of the two tight loop rollers. They do not last for ever and sometimes are so worn they have to be replaced.Lateral drift of the film in bad cases can really raise the error rate, some times to the point that tracks can no longer be read.

Mark

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003


 - posted 03-11-2018 03:52 PM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
I wonder if someone can comment on the base error rate these days, now that films are not made as often and by only one lab in the USA, anyway? It could be that the error rate has started to go back up.

I do stock the last of the Dolby LEDs, if anybody needs them. I don't have the Dolby LED in a heat sink, somebody would need to solder it in to the heatsink.I do have stock of the LED/heatsinks for BACP analog and digital reader though. I also have stock of the bulb for the Cat. 700 as well.

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Julian Antos
Film Handler

Posts: 76
From: Chicago, IL, USA
Registered: Nov 2009


 - posted 03-12-2018 01:51 PM      Profile for Julian Antos   Email Julian Antos   Send New Private Message       Edit/Delete Post 
The last few NEW prints I've run have gotten 0s and 1s no problem.

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Louis Bornwasser
Film God

Posts: 4441
From: prospect ky usa
Registered: Mar 2005


 - posted 03-12-2018 09:29 PM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
I also have hundreds of Dolby LEDS. Also a few of the ones in the heat sink.

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003


 - posted 03-13-2018 12:26 AM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
So, sell them already. You are very hard to catch.

How many new 650's you have in stock?

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Garry Knapp
Film Handler

Posts: 50
From: Mississauga Ontario Canada
Registered: Oct 2016


 - posted 03-13-2018 05:22 PM      Profile for Garry Knapp   Author's Homepage   Email Garry Knapp   Send New Private Message       Edit/Delete Post 
WOW...thank you guys for all the great input...I don't know where to start. I can't figure out how to reply individually, so i'll just reply to everyone.
Marco: I have a CP65...
Randy: most of my prints read pretty high...6-7 range. I do get a few times where it falls off and reverts back...
I've been trying to get a hold of someone up here, but the person is very busy it seems...
I run a vic5...theres not much tension adjustment options that I know of...
It's not terribly old either. It only ran in for 7 years before it was pulled out.
Mark J.: Cleanliness helps, this I found out...I will add the film guard to my cleaning unit (kelmar) Haven't been...
Carsten/Gord: Yes, its a basement reader...not much to play with as far as adjustments...It runs LEDs

Thanks everyone...this will help things quite a bit.

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Max Hayman
Film Handler

Posts: 16
From: London, England
Registered: Jan 2015


 - posted 03-13-2018 05:23 PM      Profile for Max Hayman   Email Max Hayman   Send New Private Message       Edit/Delete Post 
hmmmm I always thought a higher number was better...thats not good...our SR-D head seems to stop working every now and again.

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