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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » Not getting anything from To Power Amps

   
Author Topic: Not getting anything from To Power Amps
Mitchell Cope
Master Film Handler

Posts: 256
From: Overland Park, KS, United States
Registered: Jun 99


 - posted 06-19-1999 04:42 PM      Profile for Mitchell Cope   Email Mitchell Cope   Send New Private Message       Edit/Delete Post 
I just got a Dolby CP50 loaded with cards (Cat 108, 22, 109, 110 bypass, 150, 64, 117, etc.) . I'm getting a good signal from the Pre-Amp Outputs terminal strip, but seems like nothing from the To Power Amps terminal strip. I don't have a manual and I'm not familiar with the equipment, so I'm wondering if I'm doing something wrong. Any ideas?

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Mike Blakesley
Film God

Posts: 12272
From: Forsyth, Montana
Registered: Jun 99


 - posted 06-19-1999 06:10 PM      Profile for Mike Blakesley   Author's Homepage   Email Mike Blakesley   Send New Private Message       Edit/Delete Post 
Did you try re-seating all the cards? (take them out and put them back in) That has saved my butt I don't know how many times.

------------------
Mike Blakesley

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Brad Miller
Administrator

Posts: 17638
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 06-19-1999 06:50 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Check your cat 117 fader card. The pots are probably turned down. They are the 4 tiny screwdriven pots (usually blue or black) towards the bottom of the card labeled L,C,R,S. It is also possible the cards are not in the correct slots. Verify this with the markings on the back of the face plate. I don't have a CP50 manual handy, but if you aren't using a subwoofer card cat 160, you MUST have the bypass blank card in it's place...I believe it is cat 110, but not sure of the card number offhand.

If nothing works, email me directly and I will pull out the manual for reference and talk you through it on ICQ or IM. I can also photocopy the manual if you need.

Good luck.

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Brad Miller
Administrator

Posts: 17638
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 06-19-1999 06:52 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
F.Y.I. The Dolby trimpots are typically 18 turn pots...meaning they do not turn from 7PM to 5PM on a clock, but require many full turns of the screwdriver to make a difference. You can usually tell when you've hit the end by a faint clicking noise in the pot.

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Mitchell Cope
Master Film Handler

Posts: 256
From: Overland Park, KS, United States
Registered: Jun 99


 - posted 06-20-1999 01:18 PM      Profile for Mitchell Cope   Email Mitchell Cope   Send New Private Message       Edit/Delete Post 
I reseated all the cards and made sure they were all where they were supposed to be. The 110 bypass card is inserted with the 110 bypass arrow pointing back (as opposed to the 160 bypass arrow pointing back). I've switched the three Cat 64 cards around to see if this had any affect. I changed the pots on the Cat 117 card and could hear just a trace of some hiss (this is with my amplifier turned all the way up). I getting an expected popping sound when I turn the CP50 on and off, so the terminal strip is not dead (plus I have that faint hiss as well). I have the four shorting strips all set to high level output. I measured points on the backplane and terminal strips marked +12v, -12v, and +24v and all those voltages were there.

Like I said before, I'm getting a good signal from the pre-amp output.

On the back board, there's a shorting strip labeled from top to bottom L, C, R, S, 0v, and the sixth position is unmarked. Over this shorting strip is marked Cat 223. L, C, R, S positions all have shorting terminals in them. The bottom two (0v and unmarked) do not. Would this make a difference?

Thanks for the help guys. If this set of clues doesn't help, then I'll probably want to get that manual (probably need one anyway) and jump into more specifics.

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Brad Miller
Administrator

Posts: 17638
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 06-20-1999 02:34 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Let me think about that one. It's been a long while since I've worked with a CP50.

I'll have to pull the manual out for reference. I can photocopy it for you at the same time if you would like. Send me a mailing address to my email:
Flix@film-tech.com

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Brad Miller
Administrator

Posts: 17638
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 06-21-1999 02:47 AM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Ok, I don't know why I didn't think of this sooner, but after flipping through the CP50 manual, I remembered the CP50 does not have a front panel mounted fader. (Yes, it has been awhile since I've worked on one of those.)

Go to Radio Shack and buy yourself a 100k linear potentiometer. It should only be a buck or two. Connect it to the SK2 terminal strip (center top) onto terminals #5 and 6. They should be labeled "auto fader". Now you have a volume control!

(Note: any grade two conductor wire will do and you can mount that fader in the auditorium if you wish as wire length won't be a factor.)

Hope that is all it is. Let me know. If that doesn't work, I'll talk you through some other possibilities over ICQ/IM/phone.

Also, if you want to upgrade the unit to the latest matrix decoder, SR cards or add a subwoofer output let me know, as I have plenty of extra cards for that unit.

Good luck.

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Mitchell Cope
Master Film Handler

Posts: 256
From: Overland Park, KS, United States
Registered: Jun 99


 - posted 06-21-1999 08:04 PM      Profile for Mitchell Cope   Email Mitchell Cope   Send New Private Message       Edit/Delete Post 
The 100k pot did the trick. Thanks Brad. I never would have discovered that without the manual or some forum help.

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