Film-Tech Forum ARCHIVE: CP-65 help..... buzzzz

This is topic CP-65 help..... buzzzz in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Cris Capp (Member # 5476) on 04-16-2013, 07:16 PM:

Hello,

Having some trouble with our CP65. There's a strong 60 hertz hum present in the system. Today we ruled out other building related equipment like blowers, pumps, flourecent lights, and chillers.

What I do know is that if I remove the Cat 242 card... the buzz stops. Also if I put it in Bypass mode, it stops. Any advice on what to do next? Thanks

Posted by Tony Bandiera Jr (Member # 2365) on 04-16-2013, 08:59 PM:

Cris:

OK, time for troubleshooting 101: [Smile]

Is the hum the same regardless of what format is selected? Or does it go away in non-sync or external 6ch modes?

Is it in all channels, or only in select channels? If so, which channels are humming?

Did this come on suddenly? Were there any power issues or outages just before it started? Any equipment changes?

Let's get those answers first and go from there.

Posted by Richard Hamilton (Member # 321) on 04-17-2013, 09:22 AM:

quote: Tony Bandiera Jr
troubleshooting 101

Tony, do they still teach that course? It's a blast troubleshooting over the phone especially when the theater is in another country and there's a language barrier and time difference. That's the advance course [beer]

Posted by Tony Bandiera Jr (Member # 2365) on 04-17-2013, 10:42 AM:

LOL Richard, sadly they do not teach it anymore. It has gone the way of film projectors due to d-cinema and the NOC concept. [Razz]

Hell, even here in the US I still remember nightmare phone calls to my theatres during my RCA service days when the calls went something like this:

Me: "What seems to be the problem?"
Them: "I can't get any sound."
Me: "Did you check the breakers?"
Them: "What are breakers?"
Me: "The little black things you turn on every morning."
Them: "Oh. Yeah I think so."
Me: "Well check them again and be sure."
Them: "Uh, ok....." (Long pause and random noises in the background) "Uh, yeah I think they are all on."
Me: "Well are the amplifiers and processor all on? "
Them: "What?"
Me: "All of the things in the big black tower (no one knew what a rack was) next to the projector."
Them: "Uh...yeah they are all on."
Me: "What format is the processor set to?"
Them: "What's a format?"
Me: "(sighs.) "I'm on my way over."

Only to find that they didn't have a clue and one of the breakers WAS still off, the one to the processor. [Roll Eyes]

The other favorite response was what kind of projector they had (for theatres I hadn't been to) and they always said "Christie", "it's big square and light blue." [Big Grin]

Posted by Richard Hamilton (Member # 321) on 04-17-2013, 11:23 AM:

Tony,
Same stories here. I had one almost identical to what you just said, only the amps were switched off at the rack. I was spending a nice Sat afternoon with friends and family. Kids in the pool, burgers on the grill, beer in hand and couldn't solve the "problem" over the phone. As soon as I hit the top of the booth stairs, I saw it, walked over to the rack, turned the amps on and walked out without saying a word to the manager who I went through everything over the phone with. Ahhh...the good old days [thumbsup]

Posted by Robert Koch (Member # 3728) on 04-17-2013, 01:40 PM:

One of the calls that drove me to retirement was a call from a theater 100 miles away was the complaint that "the sound is freaking out". No more info. This was in the opening days of ushers being introduced to the wonders of the projection room.

Posted by Louis Bornwasser (Member # 3063) on 04-17-2013, 02:57 PM:

Here in Lentucky, most of the folks outside of Louisville are born with a language disability. For example, they say: "Ladders." You have to know they mean "Letters, like up on the markey!" "Bat-tree" is really battery; "whirlybird" is a ceiling fan, etc.

Simply put, if they can say sound, light, or mechanical, I took EVERYTHING with me. (I need a bigger plane!) Louis

Posted by Sean McKinnon (Member # 612) on 04-18-2013, 11:14 AM:

Lol in New England taxi slang a "whirly bird" is a round trip for example "car 2 pick up 22 Main Street he's making a whirly bird to the store"

Sorry for the off topic post.

Posted by Cris Capp (Member # 5476) on 04-18-2013, 04:52 PM:

Sorry for the late reply.... been super busy here lately. To answer your questions Tony:

Buzz is present on all channels, all the time.

However... I had thought that it was at a low level, on all source selections. But I went to double check today and found to my suprise that now some sources are at a new unbearable level.

Source:
Mono- very low
Dolby Stereo A- unbearably high
Dolby stereo SR- unbearably high
Dolby Stereo digital- very low
Non sync- medium low
Mag- very low

I do think that some blackouts in years past (car hitting power poll) may have started things though I can't say that definitively.

Only equipment changes we did were installing BACP reverse scan readers, and Dolby 702 digital heads, plus a DA20. When these additions were done, the buzz was present on all channels and all sources at a low level.

The new super loud buzz on Dolby stereo A and SR settings is completely new.

Posted by Sam D. Chavez (Member # 1841) on 04-18-2013, 06:41 PM:

How about when you put the processor in bypass?

If the hum is still there and goes up and down with the fader it's either the 240 preamp, the reader power supply, or the cabling between.

If the hum goes away when in bypass, it could be the 222, 150 or the 249 power supply. The fact the hum is louder in stereo than in Mono suggests the 222 or 150 card but just a guess.

Posted by Cris Capp (Member # 5476) on 04-18-2013, 07:28 PM:

Hum goes completely away in bypass.

I guess I'll try to buy a used CP65 so I can get some backup cards to test with.

Posted by Tony Bandiera Jr (Member # 2365) on 04-18-2013, 07:43 PM:

Cris, check your PM inbox......