Film-Tech Forum ARCHIVE: Tracking down an intermittent sound problem.

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Posted by Brian D. Whitish (Member # 825) on 05-23-2011, 10:35 AM:

I am going crazy trying to track down an intermittent sound problem. It is a high pitched whistling out the surround speakers. I can happen several times in a day or not at all for several days. When it happens I turn the amps off. Usually I can turn them back on for the next show and its fine again for the rest of the day. Equipment is Qsc 1500a amps, CP500, Surround EX unit, and component engineering monitor. Have replace one of the two surround amps in the last year and it still happens.

Posted by Louis Bornwasser (Member # 3063) on 05-23-2011, 11:13 AM:

Do you have another CP-500 where you can swap ALL of the boards?

Is the small jumper added to the chassis ground to the output low? (Only on later instruction manuals; first ones were wrong.) Louis

Posted by Andres Briano (Member # 4621) on 05-23-2011, 03:45 PM:

I´ve had this problem before. If you switch the SA10 (EX adapter) to Bypass, it´ll go away. That´ll solve your problems in the short term. I have not been able to fix it in the long term.

Andrés

Posted by Christopher Schaffner (Member # 6132) on 05-25-2011, 09:39 PM:

I had the same problem before too. putting the SA10 in bypass also fixed it

Posted by Tony Bandiera Jr (Member # 2365) on 05-25-2011, 09:43 PM:

Sounds like one of the op-amp chips in the SA-10 is oscillating. Best advice is to get rid of the SA-10 altogether. I don't think Dolby even supports it anymore.

Posted by Chase Taylor (Member # 778) on 05-26-2011, 12:35 AM:

Same hear with the SA-10. Pulled it and the problem went away!

Chase

Posted by Brian D. Whitish (Member # 825) on 05-26-2011, 04:05 AM:

I tried putting mine in bypass, but it didnt work. I do think the sa10 is the problem. Im going to take it out and see what happens. Thanks for the ideas. I was sure not able to figure it out.

Posted by Mark Gulbrandsen (Member # 72) on 05-26-2011, 08:59 AM:

If you have to have EX I know where there is a stack of Panastereo EX units sitting that have also been pulled out.

Posted by Tony Bandiera Jr (Member # 2365) on 05-26-2011, 12:51 PM:

Yeah, great idea Mark, let's remove something not supported by its' maker and replace it with something worse.... [Roll Eyes]

Posted by Gordon McLeod (Member # 33) on 05-26-2011, 02:25 PM:

What is wrong with the Panastereo equipment?

Posted by Tony Bandiera Jr (Member # 2365) on 05-26-2011, 04:56 PM:

Gordon/Mark, disregard previous post, had early morning brain fart and mixed my brands up...oops.

Posted by Eric Robinson (Member # 2966) on 05-30-2011, 01:17 AM:

I have sent several Dolby EX units in for repair to curtail this problem. The annoying thing is that it pisses off all the customers because they are the ones who have to report it. Sometimes you can cure it yourself for a short period by pulling the EX motherboard from the backplane and reseating it. I have had one in bypass for over 6 months and I am planning on removing it from the audio system all together.

Posted by Ian Parfrey (Member # 5122) on 05-30-2011, 04:15 AM:

Well, Smart DID buy Panastereo .. unfortunately. [Roll Eyes]