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Author Topic: Benchtesting CP50 and CP65 Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 06-03-2007 01:22 AM                     Hello , I received a few CP50 and CP65 as part of a deal and I'd like to know if there is a way to bechtest htem, without having to hook it up to a sound reader and do all hte set up for it. Basically what I want to do is checking them to see what's working and what isn't,reset preamps,equalizer input/output levels and so on.. make sure the CAT150 are working ok and calibrate the CAT64's input/outputs (often found mis-set here) before sending them out .I don't have a working projector at the moment (mine are dismantled ,parts lying all over the place in boxes and cans waiting for free time to work on them)to run test films then an external device to generate a signal is needed.. but I don't know what signal and level to use for hte test, need some input on it too. Thank you  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 06-03-2007 07:46 AM                        The B chain is simple; just generate the tone or pink noise and measure it on a scope. The A chain wants to see a signal about equal to a microphone; so -55 or -60 db should do it. You could use the output of another CP to generate what you need and pad it down appropriately. Louis  |  IP: Logged Kenneth Wuepper Phenomenal Film Handler Posts: 1026 From: Saginaw, MI, USA Registered: Feb 2002 posted 06-03-2007 11:56 AM                     If you have the sound head for your projector with the motor in running order, you could make a small accululator for 10 or 15 feet of audio test film and feed the scanner output signal into the various processors you are testing. The advantage to this system is your ability to have a known source for comparing all of the processor units tested. The signal could be from various changeable loops of test film, Pink noise and Dolby Tone. The picture portion of the machine is not required for your testing purposes. KEN  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 06-03-2007 12:22 PM                        But Ken, Luciano siad he did NOT have a working projector or even just sound head available right now. That was the whole point of the post. As Louis said, testing the B chain related components is easy, and the A cain components can be tested by feeding them a tone from a generator, too. I have never done that, but I believe a level of about 120mV should be appropriate for the projector inputs. However, that needs to be confirmed by somone who has actually done that "on the bench". But - Luciano, you can not set up the A chain on the bench and then just send the units out for plug and play. Each individual projector and processor combination needs to be aligned. That is the whole point of the A chain alignment process. You do not know how well a projector is aligned until you hook it up to the processor and play the test loops. Even if you know that the projector is well aligned as far as left-right, illumination uniformity, focus and azimuth are concerned, you still need to calibrate the level within the actual setup.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-03-2007 02:43 PM                     120mV at the projector inputs is WAY too high...however here is a little trick that will work with ANY Dolby preamp (and probably most others)... For each channel use two 47K resistors...one each on the positive and negative terminals (4 resistors total for both channels)... You can then connect any normal line level source to the inputs via the resistors (the resistors are used in SERIES with your signal source)...you can use a signal generator, CD player...whatever you have.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 06-03-2007 03:32 PM                        What's the correct voltage coming out of the preamp when the Dolby level is set? It's not 300mV, but I can't remember exactly what it typically is. Apparently not 120mV.  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 06-03-2007 04:18 PM                     Hello again, Atr hte moment, I don't have anything I can run a film loop working,both of my projectors are in pieces. I know the A-chain can't be done nor anything else but that's not the intention at this moment. I just want to test and make sure the processors are in working order and verify the internal level setups ( mostly hte CAT64 inputs/outputs levels, since htose are often messed up by others in the theatres around here resulting in saturated output cards,distorted signals or then low levels in the auditorium and high noise. Also want to make sure the CAT150 is working right. (fortunately one of the CP50 and the 65 has the CAT150E,only the ohter CP50 has a lower version,dual card CAT150D if I'm not wrong) Is there any use for the dolby tone generators built in the NR modules? ( liking the test points on the meter cards in the CP50 activates it) would it be suitable to set the equalizers in/out levels? Been a while since I had to deal with those old processors that I forgot most of the procedures for them Luciano  |  IP: Logged Ben Wales Jedi Master Film Handler Posts: 602 From: Southampton. England Registered: Jul 99 posted 06-03-2007 05:03 PM                     All the Internal Dolby Tone was a Signal Level, ideal to check you get signal path through the CP50. You will need a Cat85 (Pink Noise) Gen card to set the EQ, make sure all the Cat64 (input) are set to min and adjust the output to 150mv, also the 27 1/3octave pots are set flat, ie 12oclock position. I would make sure the output card gain is turn down, say 5 turns on each channel as a starter, before all that I would check the Solder joins on the Back Plane of the CP50 as that tends to be a issue with dry joins.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 06-03-2007 07:57 PM                       The 2 Dolby tone signals from the CP50 will not stay in phase with each other so are not much use except to tell you the Cat. No. 150 is steering the audio signals randomly all over the place; kind of like a car with no steering wheel.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 06-03-2007 08:21 PM                        Sam - why? Please explain further! What's the input range of voltages that can be accepted coming from the solar cell preamp and accomodated by the level range on the processor's preamp card, and what is the voltage of the signal coming out of the preamp card?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-03-2007 09:16 PM                     The output of all Dolby optical preamps from the CP50 onward (I'm not sure about the CP100 nor the digital units since it may be in the digital domain at that point) are at 300mV. You CAN use the Dolby Tone of the Cat 22s to set up the Cat 64 output trims IF you only use one Cat 22 (say left channel) and then switch each EQ card into the Left position and set your 150mV level (referenced on the Cat 111, 117 or Cat 517). As others have mentioned...since Dolby Tone resides in the 800Hz region (and is modulated)...one should have at least 630, 800 and 1K pots centered before setting the output trim. Steve  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 06-03-2007 09:49 PM                     Lonnie had told me a better and more accurate way to set the Cat 64 card outputs with the pink noise gen., but I forget exactly how. Maybe Sam knows.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 06-03-2007 10:04 PM                        quote: Steve Guttag The output of all Dolby optical preamps from the CP50 onward (I'm not sure about the CP100 nor the digital units since it may be in the digital domain at that point) are at 300mV. Here is where I am getting confused a little bit, because in many cases when I measured the output from the analog preamp card after setting Dolby level, I found the level more around 233mV. Or was it 266mV? I can't remember now. In any case, markedly lower than 300mV, a greater deviation than can be explained by the known variance in some color stock test loops.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-03-2007 10:05 PM                     Yes, in the day, I used the PN card since then you don't need to fool with worrying about where the individual frequency bands are set. However you really need an analog meter with you to do it right. The level one set escapes me at the moment...it has been a LONG time since I've needed to reset a Cat 64a.  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 06-03-2007 10:47 PM                     Hello again, Steve, thanks for the information regarding the pre-amps output levels and the tip regarding the use of internal Dolby tone generator to reset the CAT64. I could only start the works in one of hte CP50 and already got a busted CAT150, it doesn't surprize me it's the older,dual card version. it's surround channel is popping and hissing almost constantly, with or without signal, it's the last of the dual card CAT150, I believe, since it has the signal leds in it. Also found a few damaged trimpots in one pre-amp card and thoseold,grey,can-type capacitors in the PSU with the usual brow stuff leaked out and dried.a little bit of fun for hte next day's nights. and yes, I have those analog audio AC meters and signal generator Going to use the meter soon on them And I did notice hte effect Sam mentioned in his post, having the two NR cards in with the signal activated,the center chanel puts out a weird ( to ears) signal and the surrond comes and goes at random. While I'm doing the testing, I'm using a small bech amplifier. will save hte big one for the final testing,so I can really annoy the neightboors Thanks again!  |  IP: Logged

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