This is topic Having a BIG HF problem with Smart MODIII in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Aaron Flack (Member # 517) on 10-31-2000, 03:06 PM:
Nothing frustrates me more than sound problems, especially when I can't find it. Back in the summer we put MI2 in one of our small theaters and customers started to complain that they couldn't understand a word of vocals. To me it sounded like listening to a cassatte tape with the treble all the way down, probably worse. I didn't want to mess with the equalizers because I knew they hadn't been touched. Since the music format sounded o.k. I thought it was the sound head so I cleaned the solar cell and lens, but that didn't help. B.T.W. I knew it wasn't the print. But the strange thing is it seemed to have fixed itself suddenly after a few weeks. Now it's doing it again. I have followed the wiring from the solar cell to the processor(most of it is jumbled together), and couldn't find a problem. The only thing different that I've noticed is the preamp LED's show the left channel jump whenever someone speaks, and most of the effects sound comes from the right. And when it's in mono all sound comes from left channel.
Posted by Brad Miller (Member # 2) on 10-31-2000, 04:18 PM:
Your preamp levels are definitely off and you may need an A-chain alignment as well. Also, you could have a center channel crossover that is working intermittently.Do you have a Dolby tone loop?
Posted by Gordon McLeod (Member # 33) on 10-31-2000, 06:31 PM:
Check the A chain and also check again the cell wireing and even the condition of the cell
also check the powersupply as I once had a mod3 go a bit snaky and it was due to one of the wall worts
Do you have a SR adapter connected to it?
Posted by Marc Jones (Member # 29) on 10-31-2000, 09:29 PM:
Check the A Chain like suggested above, if you have correct equipment to do so. You possibly could isolate whether or not its a B-Chain problem by your house music and isolating each channels and this could point you in the direction of loose connection, bad amplifier or bad HF Driver.
Good Luck
Marc Jones
Posted by Aaron Flack (Member # 517) on 11-01-2000, 12:19 AM:
Unfortuanitly, I do not have test loop or buzz track to run through the soundhead, and probably neither does anyone else locally under Carmike due to low interest in screen presentation. But I did learn over time that many of our audio problems were due to the position of the exciter lamp. I also learned that I could inacurately balance the left and right channel with stereo screenvisions and some trailers by monitoring center channel vocals or one sound effect that has been split for stereo, like a percussion. I do not have any profesional sound testing equipment but I do have an oscillascope(sorry about spelling) and I might could get an RTA.
No, I we do not use SR cards because the MODIIIB doesn't support that format, only Smart NR. Just to let you know, the theaters with that model processor use a single split-channel amplifier for one front channel and wall surrounds.
Posted by Gordon McLeod (Member # 33) on 11-01-2000, 08:50 AM:
Almost all front surround systems rely on just a L-r signal going to the surrounds so balanceing the A chain is extremely critcle
Also the Mod3 was designed to support SR with an external adapter and the reason I asked was related to a posible problem there
Posted by Aaron Flack (Member # 517) on 11-01-2000, 01:39 PM:
I think that if the A chain was truly misaligned, then there is no way it could have mechanically fixed itself the last time this happened in July. Even though the preamp shows a horribly unballenced signal, when I listen inside the theater 80% of the sound tries to come from the center and the left and right surrounds are indistinctive. The high is so cut you can't hear a shread of noise. When attempting to adjust the exciter lamp all it does is dim the sound.
I will point out that lamp has gone in and out during movies lately, probably just a bad wire.
Posted by Gordon McLeod (Member # 33) on 11-01-2000, 02:21 PM:
Climb up and check if the HF is producing any sound
there is an internal Pinknoise generator in the Mod3 so you ahould here something comeing out the HF horn
If it is Biamped? check the amp that is driving the HF horn
Posted by Greg Pauley (Member # 503) on 11-01-2000, 05:54 PM:
Aaron:You keep talking about adjusting the exciter bulb, are you sure you have the bulb aligned to illuminate both tracks? Take a piece of paper and place between the cell and sound lens and move the exciter bulb in/out until you get equal illumination over the slit. You are really shooting in the dark trying to adjust using anything other than proper test film with sound gear. You could end up creating other problems for yourself, but if Carmike can't afford buzz track or a sound tech what's a guy to do?
Posted by Aaron Flack (Member # 517) on 11-02-2000, 01:35 PM:
I think I should get a little more credit here. Not only do I know where the light should shine directly, I can also see where the light flickers on the solar cell indicating the dynamic of the sound(it is extremely small of course). I have checked the aligned position of the solar cell and it's rock solid, probably hasn't been moved in years. The only thing that I can see wrong is the beam from the lens is a little dim, even with new brightly lit lamp positioned perfectly for maximum output. But thats a long shot for causing my problem. Beleve me, I have improved sound in other theaters greatly with minor adjustments from the lamp and lens, but I have never touched the focus for technition reasons.
I will check the HF driver as suggested, and remind you the music format sounds OK to me.Hey, where is Oscar in this desperate time?
Posted by Randy Stankey (Member # 64) on 11-02-2000, 05:42 PM:
I'd say check the easy things first:Are your speakers/drivers all working? (It has been said above that the Smart processor has a P.N. Gen.) I know you've said music sounds good but recorded music off a tape or CD and film sound aren't quite the same thing. Wiring between the rack and the speakers is something that could be looked at. (An ohm meter would be handy.)
It has been said above that you should climb up behind the screen and personally check. I agree.
Second, I'd look at the amps. This may sound stupid, but are they all hooked up properly? I've seen a LOT of tinkering and when you ask what happened, nobody knows anything. (Boy! I'd like to get my hands on that Nobody guy!) Use your booth monitor to switch between "processor" output and "amplifier" output. (If you have the kind that can do that.)
By this time you should have a good idea where the problem lies. If you have eliminated the speakers, wires and amps (and crossovers) you're left with only two possibilities: The A-Chain or something inside the processor. Personally, I'd verify the A-Chain before I go tearing apart the processor. (Again, I do the easiest things first.) Besides, you've mentioned that the A-Chain had been adjusted without the use of a scope and test film. I don't doubt your ability to do it "by ear" but there's no substitute for doing it with a scope. You'd be suprised at the difference it makes. You can do a really good job at "fixing that baby up" and then you scope it out and it sounds 100 times better.
Now, we're left with one place where the problem could be. The processor. Can you swap out the cards with another house that's known to be good? Take a piece of tape and write the house numbers and slot positions on the cards. (It sounds corny but do it. I, myself, have mixed up cards and it's NOT fun trying to sort them out again!) You should be able to make some educated guesses at which card it might be. (The N.R. card, for example.) By this time you SHOULD have been able to pin down the problem. If not, you certainly know where the problem ISN'T.
Sorry, if I sound like I'm talking down on you. I don't mean to. Let me say this: Do you know how many times I've had problems and had somebody walk up to me and fix it in two seconds? More than I'll ever admit! 
I guess you could sum it up by asking yourself, "Is the TV plugged in?"
Posted by Jon Bartow (Member # 241) on 11-02-2000, 06:05 PM:
What kind of projector is it? The reason I ask is, I had one screen once that had a problem similar to you problem. It was a Simpex 1050. Turned out that the excessive oil leaking out of the projector had penetrated the slit lens causing the light to be filtered/distorted. If you have an oil leak you might try cleaning the lens off with a lens cleaning solution (not windex). Of course don't remove the lens unless you're prepared with a scope and RTA to recalibrate 
Posted by Aaron Flack (Member # 517) on 11-06-2000, 08:30 AM:
That last post gave me an idea. We're running Simplex PR1014 projectors which are at least 20 years old since they are from National Theater Supply, not Strong. Two, including this one, are not 5-Star soundheads but some older model which I don't remember the number but the door has no window and it uses a Howell motor with a large flywheel. Anyway, you said that oil could have accumullated on the lens to cause distorted sound. I had rulled that out since I throughly cleaned all lens surfaces. But the day I discovered the problem the first thing I noticed was the front piece of the lens was loose. Lately that projector has had terrible oil leakage from some idiot over oiling. But what if a tiny amount of oil got in that slightly loose lens? The last few days, the sound has gotten much louder and the solar cell is brighter, but still a little blurred. Could this explain the bad clarity?