This is topic Frying eggs on a CP200 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Nick Perry (Member # 361) on 06-29-2000, 04:01 AM:
Dear all,I have encounted a slight problem that I was hoping someone else had experienced. I have two projectors hooked up to a CP200. One has an exciter lamp based soundhead and the other I have just fitted with a reverse scan LED reader. After installing the new reader and getting the alignment spot on, I ran some film and got this crackling sound through the front loudspeakers like eggs frying. Most people whould say this is an old/dirty cell or dirt on the optics but after cleaning these elements the problem remained. I then ran some film on the other projector and found it has exactly the same problem. This has led me to beleive that the problem is not with the soundheads but the processor. The sound is only obtrusive when there is little signal however could prove to be annoying. The CP200 is equip with the old cat 108 optical pre-amp card. Could this be part of the problem or is it something else?
Apparently this sound has been present for some time now.
P.S The loudspeakers and amps are fine. It is crystal clear in SR.D
Regards,
Nick
Posted by Russ Kress (Member # 461) on 06-29-2000, 05:20 AM:
How (and where) is the shield wire connected on the reverse scan reader? I know that they say to connect it at both ends (processor and reader) but I have had to go back and lift it on the projector side in most installations.Russ
Posted by Brad Miller (Member # 2) on 06-29-2000, 06:36 AM:
So the problem happened AFTER you upgraded ONE of the projectors? I think you've just answered your own question. So what if you completely disconnect the wires into the CP200 on the newly upgraded reverse scan? Does the egg frying problem go away?
Check your wiring over on that and get back to us. 
Posted by John Walsh (Member # 168) on 06-29-2000, 08:20 AM:
We just fixed a problem like that. There was a cracking sound while film was playing. It only did it for awhile after the film was started.Turned out to be the Component Eng. reverse scan LED reader. The tech who looked at it said that usually it's the wire screw terminations on the back (they get loose), but in this case it had to be replaced.
Posted by Nick Perry (Member # 361) on 06-30-2000, 04:48 AM:
Sorry, I should have made myself a little more clear! The problem was present before the upgrade. After speaking to other people today who have worked at the location, the problem has been there for a couple of years. It really isn't that bad and most people would not pick it up but I am curious as to the cause. I am convinced that it is not the soundheads. Even disconnecting the new one does not eliminate the problem on projector 2 nor vice versa.
Russ, I shall remove the sheild of the reverse scan and have a listen.Thanks,
Nick
Posted by Gordon McLeod (Member # 33) on 06-30-2000, 10:57 AM:
Does the system have mag capabilities
Try playing some magnetic film and see if it is there
Also try sending a video or audio tape into the magB input and create a format that routes the mag b input to the cat 150B (printmaster operation)
It is possible that an older 150 card is dying
Another possibility of frying eggs is the bypass relays either having corrosion on there sockets or internally
try going to bypass and see if the problem goes away
Also is it there when nothing is playing?
check the powersupply
Posted by David Kilderry (Member # 142) on 06-30-2000, 06:54 PM:
Nick,I consider it could be one of a variety of cards. The processor is now 16 years old, but from memory we a few spare cards for the CP200 in the store.
Is it only audible on optical film sound? If so I would not discount a static charge building and arcing across to the cell.
As stated, test in bypass to start narrowing down the possibilities.
David
Posted by Gordon McLeod (Member # 33) on 06-30-2000, 07:32 PM:
Russ Dolby published a engineering note recomending that each channel be a 3 conductor cable + - E and the shield left floating as always at the projector end
Never had a problem when done that way
Posted by Steve Guttag (Member # 268) on 06-30-2000, 08:14 PM:
Since it only happens on optical you are a good part of the way home as to finding the cause. Since it has been happening for 2 years you can safely eliminate you new reader as the cause as well.You didn't mention if it happens on Non-Sync or not. If it does, then there are only a couple of cards left or the DA-20 has a noisy connector from JM-11 or relay contact. If the problem is just on optical then we have narrowed the problem quite a bit.
One thing to check is the solder connections on the card connectors mounted to the back plane. Rewet them and many strange intermittent problems will evaporate.
What channel is it in? All or just one? The most likely suspect is the Cat 150 for most noise and only optical related in a CP-200
If you are running an older Cat. 108 (prior to the Cat. 108C) then you should upgrade as a matter of course (I doubt it is the source of you noise, but certainly possible, it is just that both projectors share rather little circuity on it). The Cat. 108C will match your new reader's (or narrow slit lens') response MUCH better. With the Cat. 108C you can expect a cleaner, quieter response and MUCH flatter in the high frequencies.
Steve
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"Old projectionists never die, they just changeover!"
Posted by Nick Perry (Member # 361) on 07-01-2000, 03:40 AM:
Dear All,Gordon, Yes it does have Mag capabilities so that's another thing I will try as well as swapping over the C150. Interesting what Russ said about 3 conductor cable for each channel. If I get that desperate i'll do a rough cable run using that method and see how I go.
Steve, it is not present in Non-sync. I don't think it's the DA20.
I'll try to see if we have a 108C floating around. It's worth one anyway now with the improved HF response we get from the reverse scan.
David, if none of these tests fixes the problem, static could be a viable answer. Anyone else had a static soundhead?
One thing that recentlly occured to me is that the SRA5 could be faulty or not installed correctly. It does sound like i'm listening to A-type with little or no noise reduction.
I didn't have time to investiagte this last time I was on but it's worth a look.
The unit was put installed in 98 if I recall correctly.
Anyway, thanks for all the feedback. I have plenty to try now next time i'm in. I'll keep you posted!
Kind Regards,
Nick
Posted by Brad Miller (Member # 2) on 07-01-2000, 05:25 AM:
Aha! The SRA5. Yes, I remember now at one theater where the cable had come loose from the SRA5 and was causing the frying eggs sound! DEFINITELY check that. It'll cause just as many problems as the actual wire from the soundhead would if not wired in properly. I didn't even think about your having that hooked into the CP200. In fact, you might even consider removing it from the system if it the problem continues to rule it out.
Posted by Steve Guttag (Member # 268) on 07-01-2000, 08:34 AM:
Since the noise is not in Non-Sync then you can safely eliminate all cards after the 2nd switch card.This will place the noise problem between the 1st and 2nd switch cards.
So what is left? Cat. 22s, Cat. 109Cs, the SRA-5 and related wiring, Special 1 (and possible poor soldering for SRA-5 modification, Cat. 160 (could be putting noise on the Lt, Rt lines), Cat. 150 (often is the source of noise problems, if yours is a Cat. 150C or earlier, then upgrade to Cat. 150F as a matter of course for improved decoding and quieter) and finally Special 2 (again, possible poor solder joints).
Knowing which channels the noise is in will help isolate the problem further.
Steve
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"Old projectionists never die, they just changeover!"
Posted by Gordon McLeod (Member # 33) on 07-01-2000, 09:17 AM:
If it sounds like there is no A type nr sounds odd
Static from cell pickup is very possible from static on the film discharging to the cell but not a concern on the reverse scan reader
Posted by Rick Long Jr (Member # 541) on 08-07-2000, 09:56 PM:
I didn't notice wether you mentioned wether the noise was there both with the projectors running and at rest. Some other questions; does it vary with the volume control? How about wether the exiters are on or off? What kind of machines are you running? I've encountered similar problems on cinemeccanica machines when the little metal tab inside the sound drum flywheel cover wears out. As for the SRA5 with a CP 200, it is only (in my opinion) worth the bother if you are going to be running a lot of A-type. As almost all prints are SR now, you can simply remove the cat-280T cards from the SRA5 and plug them directly into your processor unit, replacing the cat-22's for left and right(There are four as Im sure you know, remove the first and third ones.) You may have to reach in to pinch the cover on the 280T's so that it will fit past the adjacent card edge connectors and in some extreme cases remove the cover on the left one, but it works. The only thing to remember is, as far as the dolby is concerned it is decoding A-type, so select format 04 and this will give you SR. Do not use 05.
Posted by Scott Morrison (Member # 165) on 08-08-2000, 04:32 PM:
If you take the 280t cards out of your SRA5 and put them in place of the left and right cat 22s, and then play SR prints using format '04', they will play back 3db (approximately 1 fader step) too low.
This has to do with the gain structure inside the cp200 and SR being developed quite a bit later. The cards may be used successfully in this manner if you compensate for the level drop by raising the fader 1 step when running analog. The problem is when running Dolby digital, whatever your fader setting, if the system defaults to analog, it will be 3db lower, making the switch quite noticeable to the audience. A properly installed and working SRA5 is a much better way to go.
Posted by Rick Long Jr (Member # 541) on 08-13-2000, 09:42 PM:
Scott, You are correct. My bad. I forgot. You can get around this by setting your Dolby levels to the top of the dots on the cat 109 meters, as opposed to the middle. And granted it would be preferrable to use the equipment as Dolby intended, but I believe Nick had mentioned that he was not entireley certain that the SRA5 was installed correctly. This may at least rule it or the 280T's out as a source of his sound troubles. Sorry I forgot to mention it the first time .
Posted by Gordon McLeod (Member # 33) on 08-15-2000, 12:19 PM:
Rick that won't work quite right iether as you are affecting the input level to the card and as such it will then mistrack the nr curve