Film-Tech Forum ARCHIVE: CP650 Sound Failing With Apogee Projector

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Posted by William Collins (Member # 3773) on 05-18-2006, 12:49 AM:

Hi all, I'm after a bit of help. I have a Dolby CP650, X-90 with Apogee Projector. this fault has been gradually getting worse an i have consulted as many people as i possibly could without the use of the internet.

When i start a film no matter whether its a new print or not, the fail rate of the digital sound is amazing, now at first thought i assumed there might be a focus issue and that it would run thought the entire length of the film, but as the film goes on, the fail rate declines and about 30 mins into any film its almost perfect again with the odd fail every few minutes or less.

I had the same trouble with one of my other projectors recently and discovered the flywheel bolt had worked its self loose, but have checked its not that problem. what can i do, does anyone else know what the problem could be?

Cheers

Posted by Sam D. Chavez (Member # 1841) on 05-18-2006, 10:14 AM:

Which Dolby Digital reader are you using? A Dolby Cat. No. 701/702, BACP DSTR-20, or a reader in the projector?

This will help to diagnose the problem.

Posted by Brian Middleton (Member # 3725) on 05-18-2006, 03:21 PM:

I've been having MAJOR headaches with this too. Our theater has 14 of these Apogee beasts using the sound readers built in the projector and CP650s. We've had sound issues on a few screens since we opened. Two of them are getting to the point now where we've had to cancel shows and give readmits. We've only been open for a little over 3 months, and our tech has already been by a few times for preventative maintenance and to fix other minor issues. The problems keep coming back, if they even get fixed at all.

This is my first post here (Hi everyone!), but I've been reading through here for the past month or so trying to figure out what's wrong with these projectors. Basically, we're getting the same fail rate issues as William, but they don't seem to get any better as the film plays. Probably 5 or 6 of our projectors are showing a high fail rate (5-7's with an occasional F). At the moment, two of these projectors are constantly back and forth between a high number and F. In these theaters the sound is pretty bad. It comes out warbling, like the sound of a bad cassette tape, as mentioned before in several CP650 threads here. Those threads seemed to think that it was due to the film not running steady. We switch it back to analog SR manually, and it's a little better, but not much.

I looked at our projector while it was running and I could see the film fluttering back and forth as it left the roller immediately after the intermittent, the one that the intermittent pad roller arm covers. I'd look up the technical name for that piece, but apparently it's a redesign because even our hardcopy projector manuals show a totally different assembly there.

Anyway, if I put pressure on that arm assembly, pushing it closed harder, the film leaving that roller steadies and the error rate goes down to 3-4. Since I can't do that myself for the length of the feature, I tried to see what I could tighten to keep it like that. When I loosened the two hex-head screws at the back of that assembly, I was able to turn the two rollers and change the pressure where the larger roller touches that cover and where the other roller touches the intermittent itself. The question is, where should they be set to? Looking at our other projectors, even the ones that are working fine, the adjustments are all over the place. This even after our tech was out less than a week ago and supposedly did complete A-chain alignments, cleaned, and tightened everything.

So, this morning, I set the bottom roller to be almost as close as possible and the top roller just about touching the intermittent. It was pretty much the only spot that seemed to make a difference. I'm worried if this might end up scratching the print or wearing things down. It did seem to fix the problem somewhat, but I'm not satisfied with it. I still get an occasional F on the CP650 and the adjustments seemed far too precise for me to believe it was supposed to work that way.
This was the only thing I could find that seemed to have any effect on sound errors. Does anyone have any suggestions? I may be completely on the wrong track. I'll have to check the flywheel bolt when I go in this evening.

I'm going to attempt to post a picture I took of the rollers. I took it with my camera phone, so the quality is kinda crummy, but you should be able to see what I'm talking about. You can see at the bottom of the picture where the film leaves the smaller roller and moves to the large one. That's where I can see the film bouncing up and down as the projector is running before I tightened the other two rollers (the two silver-handled ones near the center of the picture). When I turn the bottom one of the two, it pulls the red piece to the right closer to the film traveling over the roller next to it, which seems to help.

Well, I hope this made some sense and I'd be grateful for any suggestions anyone might have on this.

Posted by Manny Knowles (Member # 1171) on 05-18-2006, 04:39 PM:

If the situation repeatedly improves after about 30mins, I would be inclined to suspect that the splice between reels 1 & 2 is correcting a threading error.

Find the correct threading diagram and update your manual.

Posted by David Stambaugh (Member # 1102) on 05-18-2006, 04:44 PM:

Suggestion: Add "with Apogee Projector" to the title of this thread.

Posted by Steve Guttag (Member # 268) on 05-18-2006, 05:04 PM:

This really does sound like a projector issue, not a processor issue. Digital electronics normally dont self-heal though cold solder joints will cause erratic behavior.

The Apogee has had so many redesigns between the intermittent and the sound drum I can't imagine which one you have. If there isn't a "break sprocket" between the intermittent and the drum, you have an older design. The brake sprocket has a pad shoe that closes the film onto it and merely put drag (damping) on the film so the film steadies out after the intermittent as well as to apply tension to the film to cause the drum to have enough friction to keep up with the film.

What Strong seems to be missing on this design is that they have to choose...tight loop or loose loop sound...NOT BOTH, which is what they've chosen. If they want a loose-loop, they can skip the brake sprocket and have a pinch roller (That only hits the edges of the film) and also LOOSE the flanges on the rollers after the drum. Or go with a tight loop system and come with with some proper tensioners.

To investigate what the problem is, I would hook a scope up and see how it is tracking...if the data is jiggling and weaving on the scope...you have guidance issues at the scan point as well as lack of proper damping.

Posted by Richard Fowler (Member # 893) on 05-18-2006, 05:23 PM:

Greatly agree with Steve. The scope will definately help find the problem on "which" anti-flutter roller is causing the jitter. There is another brand of projector where the side weave affects the Dolby Digital which is apparent with a scope....either due to sloppy install, wear over time or corrosion issues.

Posted by William Collins (Member # 3773) on 05-19-2006, 12:55 AM:

First I must point out, and to this is mainly for Manny's benefit. This problem is occouring on more than one film, and its doing it even on new prints.

I didn't think about modifying the rollers that Brian mentions but i will have a look into it.

BTW The Projectors were brand new, and i think were made January. So i have the same setup that Brian has essentially.

Another point, I have had to start running interlocks on The Da Vinci Code, to which I had great fun sorting out. firstly I discovered that the motor controllers were sent with slightly different factory settings, so one of the projectors was accelerating a couple of seconds faster than the other.

When I run an interlock test for the first time, I noticed that one of the projectors was faster than the other, as my accumulator indicated as it slowly climbed the wall! I therefore had to modify the speed settings of the motors so that they run at the same speeds. Now I have one running at 60.2 Hz and the other at 59.7Hz, and its the one with the slower speed thats having the sound issues but even with the speeds set slightly higher or even lower than 59.7Hz the sound still remains to fail, and then slowly get better.

(Added Later due to forum rules not allowing me to post twice in a row!)

Had a look at the rollers Brian mentions and I can't see any noticeable change in the sound quality when i apply more pressure to the friction roller.

I did however try something else. The projectors I used in the job before my present one were Century's and I was told my tech that the quieter the loops sound the better for the film. This does not seem to apply in this case.

I tried making my bottom loop larger in the last film I laced up and imeadiatly the sound seems better, less fail rates instead of around 7. all the time its sitting at 4.

Lets see if it works on my next lace up [Smile]

(Added Later AGAIN! due to forum rules not allowing me to post twice in a row!)

It works. it would appear all this time it was just my bottom loop after the intermittent that was causing the sound trouble. The film I noticed the problem most with, i have just laced up and started. The sound is steady at 5 now, much better than the 7-8/F I was getting before.

So Brian, this maybe a point you would like to check out.

I would still like to hear any other suggestions on this problem, anything else that might help get this number lower!

[ 05-19-2006, 03:45 AM: Message edited by: William Collins ]

Posted by Mark Gulbrandsen (Member # 72) on 05-19-2006, 07:10 AM:

quote: Steve Guttag
The Apogee has had so many redesigns between the intermittent and the sound drum I can't imagine which one you have.

Humm, I can't help but to chuckle to myself.... I told them it wouldn't work the first time I saw it. Shades of Christie P35GP..... But at least the new Christie Cone X-35 works and works VERY well, including the basement SRD reader.

Mark

Posted by Mark J. Marshall (Member # 1409) on 05-19-2006, 08:13 AM:

Well, you could try a penthouse reader... but then you'd probably have to deal with warbling.

Or just do like we do now, and just run everything in SR.

[Razz]

Posted by Michael Schaffer (Member # 1204) on 05-19-2006, 11:46 PM:

Or you could just get better equipment. I looked at the Apogee myself and thought the soundhead design was not very...convincing. It took me several months to convince our owners that we should rsther buy some real equipment, although it cost a little more. We finally did get 14 Kinoton FP50A with basement combo reader (which is actully cheaper than any penthouse reader, so that brings the end price down a little), and as expected, they have been running over a year without any problems. I actually went to the location last night to check the situation, but here wasn't much to do. Most of the prints ran at error rates like 1 and 2.
Like my mother always says: you buy cheap - you pat twice.

Posted by Kyle Anderson (Member # 3504) on 05-23-2006, 03:00 AM:

If you're getting 4-5 to F back and forth repeatedly (even on new prints), one of the things to check for is dirt stuck to the drum - screws up the scan point focus enough to fail. Had this problem for WEEKS until I finally figured it out ><

Posted by William Collins (Member # 3773) on 05-23-2006, 04:45 PM:

I'll check the drum again. I had some news passed on to me about my equipment a couple of days ago, that might have the answer. we had an oil leak on the projector during shipment and the holdback sproket may have had some oil get into it, which loosened it. unfortunatly for me im not confident enough to pull it apart to try resolve it as im moving on to bigger and better things next wednesday, though it would be nice to have it fixed so keep the ideas on how to sort it coming!

Posted by Brian Middleton (Member # 3725) on 05-23-2006, 09:58 PM:

Finally got a chance to run up to the booth again to check on a few things. Won't be working a shift up there till Thursday, so I'll have more time then to really work on it.

Still having the really poor sound on that one projector. Not quite warbling as bad as it was before I tightened the rollers, but still pretty bad. According to the updated page I found in our manual, I'm supposed to leave two film thicknesses between the rollers I adjusted, so I do have them a little too close, but it's the only thing making it tolerable and it doesn't seem to be damaging the print.

I checked briefly for dirt on the drum and other rollers, but didn't find any. On that one projector, I can still see the film bouncing slightly at the point I mentioned in my first post. I'll experiment more with loop sizes next shift. I thread 'up' with pretty much identical loops on every projector, and only these few are giving me problems.

Another thing I should mention, because I just realized how bad it is, some (i.e. most) of these projectors have a fairly unsteady picture. I just watched Da Vinci Code at another theater last night and the picture was rock solid, the credits rolled smooth as silk. On our machines, I don't think I've ever seen credits that weren't jumpy. Up/down and even side to side. On one projector that's particularly bad, the CP650 immediately reverts to SR. Looking at the projector, I don't see the bouncing where I do on that first projector, but it's there after the next roller, the one barely visible at the lower left of the picture above.

From my limited experience, my first thought would be to increase the film tension. Looking at the indicator, most of the projectors are already adjusted towards the middle of the range. I mentioned that to one of the other operators and he said they were specifically told by the tech not to mess with the tension. Is there anything else that I can check to help steady the film? Should the tension need to be that high on these units? Our tech was just out a couple weeks ago for the scheduled preventative maintenance, but these issues have been ongoing pretty much since we opened.

Also, another somewhat related CP650 issue that's been bugging me. All of our 650s are calibrated such that 5.0 is the 'proper' volume, and we are instructed to leave it set there unless there are complaints. 7.0 is definitely too loud. Does that seem odd? Looking through the manual, it seems that after the extensive calibration required for these units, setting them to 7.0 would use those calibrated levels exactly. How do you calibrate one of these to rest at 5.0?

Well, that's pretty much it for this update. Thank y'all for bearing through my long posts and thanks for all the suggestions. Just trying to get an acceptable presentation out of these things.

Posted by Sean McKinnon (Member # 612) on 05-23-2006, 10:30 PM:

The proper calibration point for A Dolby processor is "7". This had to do when they used linear potentiometers, and to attain a good signal to noise ratio. If your system was calibrated at 5 all that means is that the Sound Pressure Levels were set to 85db (per channel, except the subwoofer which is not set using an spl meter) with the fader set at 5.0, In order to calibrate it at "7" you would have to reset the output gains on each channel with the CP650 set-up software. I dont think (but I may be wrong) that with the digital faders used by Dolby now that setting the fader at 5 would add more S/N so I dont think it compromises your system to not have them set at 7, the only problem is that almost everyone calibrates at "7" (Any CP adjustments or repairs should only be done by a qualified service engineer with suitable test equipment.)

Posted by Sam D. Chavez (Member # 1841) on 05-23-2006, 11:17 PM:

The fader issue is a real can of worms. Even though the dubbing theatre was set up to record at 85dBC at 7, it sounds too loud to many people in real theatres, so the fact that 5 runs OK does not always mean the house was set up using the wrong fader level.

The original idea of 7 of 10 was to have 10dB to spare on the volume control for any number of reasons, old prints not recorded to the Dolby standard, etc.

Today it is useful to have only 10dB to spare as too much room on the fader will lead to someone blowing a subwoofer out the entrance.

The subs in Dolby applications are set to be able to hit 103 dB max at fader 7. Add 10 dB to this and you have a very difficult to achieve SPL of 113, in a theatre of any size.

Posted by Steve Guttag (Member # 268) on 05-24-2006, 06:50 AM:

Er Sam...the subs on a Dolby Digital film, with the fader set to 7.0 CAN achieve 113dB since the digital output for the subs adds 10dB right out of the gate.

Adding 10dB to that gets one 123dB.

Anyway...another issue with the CP650 is that its 85dB is not the same as ALL previous processors...it will give you a 2 dB louder system. Why? Because the Cat 85 Pink Noise generator was set up that way...I believe it was set for 380mV output instead of 300mV. This PN level was carried into the CP500 era but was changed for the CP650 where it became 300mV reference...the net result is the PN in the CP650 is 2dB quieter which means you will turn the outputs up an additional 2dB and thus the whole system is 2dB hotter than previous processors using the exact same set up procedures.

As to the analog processors using fader setting of 7...there is the headroom that Sam mentions there is also VCA tracking. Take an older processor that used discrete component VCAs (something with say a Cat 117) and set the fader to 7 and set every output perfectly...then reduce the fader to 3 or 4 and now look at the channel to channel balance. As you get towards the lower end of the scale, they will not track as good to each other. So by putting the fater in the 1-2 O'Clock position, you also but the VCAs in an area where they should maintain the channel to channel balance better even if the fader is adjusted a number up or down.

Personally, I have always found that Hollywood mixes their films too damn loud...to the point that ruin the potential dynamic range of the track by having everything so elevated (except the dialog...it is normally too quiet referened to everything else). Larry Blake tends to mix films that are listenable at 7 though (Oceans 11 and 12 are examples). Just look for "Swelltone" on the credits. In fact, he had T-shirts made that said something to the effect of "I listened to Oceans 11 at 85dB and nobody complained."

Posted by Louis Bornwasser (Member # 3063) on 05-24-2006, 08:24 AM:

deleted...others said it earlier. Louis

Posted by Sam D. Chavez (Member # 1841) on 05-24-2006, 10:01 AM:

Sorry, where is my math? Steve is right for once. It's getting boring having the sudent correct me.

Posted by Steve Guttag (Member # 268) on 05-24-2006, 04:09 PM:

So many times, no less [Wink]

Posted by Phil Hill (Member # 371) on 05-24-2006, 04:17 PM:

I have empathy for you Sam. I HATE it when us young know-it-all punks correct the old-timers! HA! [Wink]

Posted by Steve Guttag (Member # 268) on 05-24-2006, 04:20 PM:

Now we know why you HATE so much! [Razz]

Posted by Phil Hill (Member # 371) on 05-24-2006, 04:22 PM:

But Steve, I'm a LOVER, NOT a Hater... [Wink]

Posted by William Collins (Member # 3773) on 05-25-2006, 01:28 AM:

Brian, check the rollers around the sound drum. not for dirt but for the bearings. I've discovered that one of my rollers is binding nicely, its not damaging the film yet, but its certainly not helping. best way to test this is to left all the projectors off in the morning, and just spin it with your fingers, and if it sounds louder than the rest and doesnt spin as freely then it might be the bearings have gone.

I recently discovered this on one of my two, its ok to run for now but im waiting on new parts. i was the guy who set this up that mentioned it to me. and he has spoken to strong and for some strange reason, this is only word of mouth so far so dont depend on it, the core for the roller was made just a bit to small for the bearings to fit, so when new they worked fine, after a bit they wear out, and it also explains why the sound improves. as the rollers heat up due to the heat transferance it expanded just enough to make it loosen up!

Check this out with you gear, might be the same issue!

Posted by System Notices (Member # 2357) on 12-10-2010, 11:12 AM:

It has been 1660 days since the last post.