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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » CP-500/70mm (Page 1)

 
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Author Topic: CP-500/70mm
Sigurd Wik
Film Handler

Posts: 36
From: Bergen, Hordaland, Norway
Registered: Feb 2011


 - posted 01-08-2018 05:46 PM      Profile for Sigurd Wik   Email Sigurd Wik   Send New Private Message       Edit/Delete Post 
I'm looking into using a Dolby CP-500D for processing 70mm magnetic soundtracks in combination with an old MPU-1, and I wonder if I have understood everything right. Maybe someone can help clarifying if not?

Having a CP-500D, as I undestand it I will need two Cat. 222A modules in addition to the Cat. 222SR/A for getting six channel noise reduction capabilities. Also I will need Cat. 669 adapter card and Cat. 685. And I haven't found the pin configuration of the magnetic input connector on the CP-500.

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Axel Fransberg
Film Handler

Posts: 9
From: Helsinki, Finland
Registered: Feb 2010


 - posted 01-09-2018 06:17 AM      Profile for Axel Fransberg   Email Axel Fransberg   Send New Private Message       Edit/Delete Post 
I'll trade you a CP500-70 with all the cards for a MPU [Smile]

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Axel Fransberg
Film Handler

Posts: 9
From: Helsinki, Finland
Registered: Feb 2010


 - posted 01-10-2018 12:37 AM      Profile for Axel Fransberg   Email Axel Fransberg   Send New Private Message       Edit/Delete Post 
The pin configuration should be in the install manual, it's the analog accessory connector.

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Sigurd Wik
Film Handler

Posts: 36
From: Bergen, Hordaland, Norway
Registered: Feb 2011


 - posted 01-10-2018 03:59 PM      Profile for Sigurd Wik   Email Sigurd Wik   Send New Private Message       Edit/Delete Post 
Thanks! Sent you a PM.

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Stephan Shelley
Jedi Master Film Handler

Posts: 527
From: castro valley, CA, usa
Registered: Nov 2014


 - posted 01-10-2018 11:10 PM      Profile for Stephan Shelley   Email Stephan Shelley   Send New Private Message       Edit/Delete Post 
another way is two cat 300 sr/a and one cat 222. If you ever want to do optical that will give you real sr.

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Gary A. Hoselton
Film Handler

Posts: 34
From: Portland OR U.S.A.
Registered: Nov 2005


 - posted 01-11-2018 12:29 AM      Profile for Gary A. Hoselton   Email Gary A. Hoselton   Send New Private Message       Edit/Delete Post 
The CP500 does not supply power for the MPU1, so you will need an 18V to 24VDC power supply for it. I use a Phoenix Contact 24VDC supply mounted on a DIN rail on side of rack.

If you do changeovers, you must supply a contact closure for each of projector 1 and 2 to the MPU1, to energize output relay for each of two channels on cat92 preamplifier boards to put correct projector's outputs on conductors that go to Analog input connector on CP500. I use two Schneider 24VDC relays on same DIN rail, powered by above 24VDC supply routed thru Douser relay on each projector.

From what I've seen, the cat92 preamplifier cards in early MPU1s have trimpots on front for low and high frequency gain and most have a third pot glued on for mid frequency gain. Later cards have low and high frequency trimpots on front and a round pot for midrange in middle of card so need a proprietary extender card to get at it. The last cards, cat92C I think, have three trimpots for each channel on front but no relay to switch outputs so must have solid state switching of some sort--I've not seen a schematic. The few cat92C's I've encountered did not work, they were used ones of course.

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Sam D. Chavez
Phenomenal Film Handler

Posts: 1975
From: Martinez, CA USA
Registered: Aug 2003


 - posted 01-11-2018 01:45 AM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
quote: Gary A. Hoselton
If you do changeovers, you must supply a contact closure for each of projector 1 and 2 to the MPU1, to energize output relay for each of two channels on cat92 preamplifier boards to put correct projector's outputs on conductors that go to Analog input connector on CP500
There is a way to wire the MPU so it makes an internal changeover where projector one is normally active and you use maintain ground for projector 2.

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Gary A. Hoselton
Film Handler

Posts: 34
From: Portland OR U.S.A.
Registered: Nov 2005


 - posted 01-11-2018 12:15 PM      Profile for Gary A. Hoselton   Email Gary A. Hoselton   Send New Private Message       Edit/Delete Post 
Want to improve my description of relay connection that I posted 11 hours ago, but message says time limit for editing post has expired. Here is complete post, improved:

The CP500 does not supply power for the MPU1, so you will need an 18V to 24VDC power supply for it. I use a Phoenix Contact 24VDC supply mounted on a DIN rail on side of rack.

If you do changeovers, you must supply a contact closure for each of projector 1 and 2 to the MPU1, to energize output relay for each of two channels on cat92 preamplifier boards to put correct projector's outputs on conductors that go to Analog input connector on CP500. I use two Schneider 24VDC relays on same DIN rail, wired as an RS flipflop, powered by above 24VDC supply and switched by above 24VDC routed thru Douser Pulse relay in controller (Components Engineering TA-10) for each projector.

From what I've seen, the cat92 preamplifier cards in early MPU1s have trimpots on front for low and high frequency gain and most have a third pot glued on for mid frequency gain. Later cards have low and high frequency trimpots on front and a round pot for midrange in middle of card so need a proprietary extender card to get at it. The last cards, cat92C I think, have three trimpots for each channel on front but no relay to switch outputs so must have solid state switching of some sort--I've not seen a schematic. The few cat92C's I've encountered did not work, they were used ones of course.

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Sigurd Wik
Film Handler

Posts: 36
From: Bergen, Hordaland, Norway
Registered: Feb 2011


 - posted 01-11-2018 12:48 PM      Profile for Sigurd Wik   Email Sigurd Wik   Send New Private Message       Edit/Delete Post 
Thanks guys, this is very useful.

Anyone have a Cat. 222A and a Cat. 669 laying around that you are interested in selling/renting? Or do you know of someone I can contact?

Thanks,
Sigurd

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 11729
From: Annapolis, MD
Registered: Dec 1999


 - posted 01-11-2018 12:59 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
I'm unaware of ANYONE supplying both projector 1 and projector 2 commands to the MPU-1. It defaults to 70mm projector 1. If put the link on the switch card to "Normal" both Projector 1 and Projector 2 outputs are hot at all times. The switch on the front or a remote contact closer can be used to select between 35mm or 70mm. If you move the link from Normal to Remote, then EITHER projector 1 OR Projector 2 are hot. To switch to projector 2, ground (E) the C/O terminal on the rear. For remote 35/70 selection, the 35/70 terminal on the rear selects 35mm.

I suppose, if you remove the switch card, you could use the discrete terminals to select which cards you want on line...but why? I've never seen anyone do that!

As for the various preamps. The CAT92 up through CAT92/4 had level and gap loss on the front via trimmers. They label it as HF but it is just for the head gap, not treble. It is set like a slit loss correction on an optical preamp. The MF and LF controls are single turn pots and one does need the extender to get to them.

the CAT92C moved it all to the front with LF and MF still single-turn pots. The CAT92C also has a fringing connection filter if you are running old tracks (pre-1983) with a narrower recording width but with later heads (post-1983). The CAT92C also is direct coupled (no transformers) and has a bit better range of accommodation with a high/low level link.

I'd suggest a 24VDC suppy rather than being near the bottom of the range.

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Sam D. Chavez
Phenomenal Film Handler

Posts: 1975
From: Martinez, CA USA
Registered: Aug 2003


 - posted 01-11-2018 03:07 PM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
I was waiting for Steve. He's right on point as usual.

Care to comment on why the 92Cs don't work? Gary, I can get the cards repaired by the person who designed them if need be.

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Gary A. Hoselton
Film Handler

Posts: 34
From: Portland OR U.S.A.
Registered: Nov 2005


 - posted 01-12-2018 02:00 PM      Profile for Gary A. Hoselton   Email Gary A. Hoselton   Send New Private Message       Edit/Delete Post 
Sam, Joel Miller has the non-working cat92C cards. He'd left 3 or 4 of them here for me to see how they worked, and none did, so he has them back. Sounds like an improved design. I'm running 35mm changeovers, not 70mm. I suppose Bob Leader has this working for 70mm, I haven't talked with him about it.

Steve, looking at my drawing, I see my problem was I had only douser pulse signals to work with, so built a flipflop relay to provide constant E (earth) to C/O CONTROL for MPU-1. Works fine, just have to switch dousers from one projector to the other and back at power up to synchronize flipflop and MPU-1 to CP500 initializing on projector 1. Could have put a delay on one relay coil so FF would initialize with C/O CONTROL open, but didn't seem worth doing, given tight spacing of relay socket terminals.

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Sam D. Chavez
Phenomenal Film Handler

Posts: 1975
From: Martinez, CA USA
Registered: Aug 2003


 - posted 01-12-2018 02:38 PM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
The 92C was the last version of the Dolby Mag preamp and used an active, balanced, transformer-less design. Failures are pretty rare and I'm thinking they may work but theres an issue with the circuit that turns the output on.

We used to use a mechanical latching relay coil across the douser wiring to convert a pulse to latch and then used one on the dry contacts to do a sound changeover.

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Scott Norwood
Film God

Posts: 7863
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99


 - posted 01-12-2018 02:41 PM      Profile for Scott Norwood   Author's Homepage   Email Scott Norwood   Send New Private Message       Edit/Delete Post 
This might be a stupid question, but what could possibly be the use of having both projector 1 and projector 2 inputs active at the same time? Why is this even a possible configuration?

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Sam D. Chavez
Phenomenal Film Handler

Posts: 1975
From: Martinez, CA USA
Registered: Aug 2003


 - posted 01-12-2018 04:41 PM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
Scott,

I think you mean MPU outputs.

I think Dolby may have designed the MPU that way to be compatible with the 70mm sound systems of the day. For instance, Ampex used dual Ledex switching for changeovers; so to be compatible with that arrangement, you needed to feed both Ledex projector one and two inputs. FYI, Ledex was a multi channel motorized wafer switch. Quite a nice device for its time.

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