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Author Topic: Setting Dolby Tone with Dodgy CAT 109 Matthew Taylor Expert Film Handler Posts: 186 From: Essex, UK Registered: Mar 2004 posted 09-05-2005 05:12 PM                     I have recently bought a CP-50 but it got damaged during transit from the US. Both meters on the CAT 109 got smashed. The seller is sorting out a replacement card but in the mean time, is there a way of roughly setting up the preamps by perhaps using a multimeter or something like that just until the card arrives?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 09-05-2005 05:41 PM                     Snappy answer: Yes More complete answer: Connect your meter (preferably an accurate one that reads true RMS) to the test points on the optical preamp (Cat. 108). Red is Left and Green is right...the ground terminal is still on the Cat. 109 though I think they added on for the Cat 108C...can't remember. Anyway, thread up and run some Cat 69T (Dolby tone) and meaure the tone at the test points, set both to exactly 300mV.  |  IP: Logged Matthew Taylor Expert Film Handler Posts: 186 From: Essex, UK Registered: Mar 2004 posted 09-06-2005 12:10 PM                     Thanks Steve.  |  IP: Logged Matthew Taylor Expert Film Handler Posts: 186 From: Essex, UK Registered: Mar 2004 posted 09-07-2005 10:50 AM                     I did what you said but the minimum voltage I get with the meter set on AC is 1.6v - several times too much I think. To be fair, I couldn't find a grounding point on the cat109 so I grounded the other lead on first the case and then the metalwork of the cat64's. There are 2 meter points on the cat109 - a black and white - should I be using the black? My 6v cinemacannica exciter lamp is running at 6v. Should I turn this down?  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 09-07-2005 10:54 AM                       I would bet you still have voltage wthout the projector running as in no ground when you are trying to measure Dolby level. The black wire test point is the ground. I hope you are not paying too much for a replacement Cat. 109.  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 12-18-2005 01:33 PM                     Hmmm one time i got same problem. With what kind of meter you set 300mV?? Did you use regular multimeter, digital or analog?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-18-2005 08:14 PM                     Hi Marin, Use a true RMS meter for doing this and any other meter read settings. There are many available but they do cost a bit more. Mark  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 12-19-2005 02:40 AM                     How i can know is it thrue RMS? If i do this with osciloscope what level that would be? Or can we measure with normal multimeter?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 12-19-2005 11:45 AM                     With a scope (assuming the signal is a sine wave) then measure the peak voltage and the rms is the sine of 45 degrees of it  |  IP: Logged

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