Film-Tech Forum ARCHIVE: Very spotty surround sound

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Posted by Dan Chilton (Member # 2288) on 01-08-2006, 07:15 PM:

Ever since our theater opened, a little over three months ago, we've had issues with our surrounds. Our little auditorium is set-up like so:

1 Center
1 Sub
6 surrounds

We have an Ultra Stereo JS 5/95 in the booth with a Ultra Stereo Surround EQ (JSE 05). Typically when we're listening to pre-show music or screening from a DVD, the non-sync works perfectly. However, it's hit or miss when we're running off of film.

The first time I called my tech and told him about it, he told me to switch a few of the mode switches on the back of the processor. As of now, the mode switches are set (from left to right) - on, on, on, off. The first three are labeled as F/B, with the first two having X and Y beneath them. The fourth, labeled L/R/S, is switched off. Also, on the other side of the processor above the inputs there is another set of 4 tiny switches (labeled L, C, R, S - with a low on the top and a high on the bottom). All four are switched to the off position.

At first, setting these switches seemed to make a difference... but then it started getting spotty again, so we switched out the Surround EQ with a new(er) one. Now everything's up in the air. Sometimes the non-sync plays on the surrounds, sometimes not. Some films will have surround all the way through, others won't.

And I'm not talking about "why can't I hear the surrounds during talking scenes?" I'm talking about, "why can't I hear the surrounds during loud action scenes, or scenes with lots of music - like the credits." During those scenes, there is literally NOTHING coming out of the surrounds.

Please help! I'm at a complete loss. [Confused]

Posted by Steve Scott (Member # 630) on 01-08-2006, 07:51 PM:

When was the last time the A-chain was aligned? The exciter/LED level may be out of alignment. Run a loop of Dolby Tone and adjust the preamp level with a small screwdriver as per the operator's manual.

If you are running fine in N/S, its likely something out of alignment in your soundhead. Is the format card actually switching to Stereo? You might also try turning up the output level pot on the Surround EQ card to see if you can goose anything out of those speakers.

Posted by Brad Miller (Member # 2) on 01-08-2006, 08:18 PM:

Nah, it's something else. If the A-chain was off, odds are he would be FLOODED with sound coming from the surrounds.

I'm not familiar enough to be of much help with that unit, as it's been a long time since I worked with one, but I'm sure Clint or someone else will be along shortly. [Cool]

Posted by Richard Hamilton (Member # 321) on 01-08-2006, 08:35 PM:

It has been a problem since opening? Can your tech not come and fix it? It is obviously a used unit, I would try, with the power off, remove each card and clean the contacts with a pencil erasor. Make sure they get re-seated very well. Sounds like a bad connection somewhere because the problem is intermittent. You say you replaced the surround EQ card, what about the levels and EQ settings? Do you still have the old one?

Posted by Gordon McLeod (Member # 33) on 01-09-2006, 06:53 AM:

Probably the bypass switch on the format card or the relay on the EQ card

Posted by Darryl Spicer (Member # 711) on 01-09-2006, 09:39 AM:

Does it have the older type format card in it. They have a switch on them that will turn the surrounds on and off when playing in stereo. Make sure the switch is on.

Posted by Clint Koch (Member # 1179) on 01-09-2006, 10:41 AM:

Hello Dan,
The 5/95 series dates back to the mid and late 80's so this is a pretty old unit. The reply's above are all correct and I thank these gentlemen for stepping in with the suggestions. The mode switches you mention above are in the correct positions for a front back system. I am leaning towards the relay on the surround card or Rick's suggestion of the contact. Although Darryl may also be correct with format module being the problem as the mode switches in the older format may also have lost contact. The best way to try and get this rsolved would be to call me at 805-549-0161. Once we get through this we can post the solution for the others to read. It is now 8:40 AM Pacific time on the 9th. I will be here all day.

Posted by Dan Chilton (Member # 2288) on 01-09-2006, 03:18 PM:

quote: Richard Hamilton
Can your tech not come and fix it?

He lives over four hours away, so we try to solve the majority of the problems over the phone.

quote: Gordon McLeod
Probably the bypass switch on the format card

We run the films with the SVA / SURR switches thrown. I don't use bypass.

quote: Richard Hamilton
You say you replaced the surround EQ card, what about the levels and EQ settings? Do you still have the old one?

It was a fix and switch replacement. I sent the old one to my equipment dealer who in turn sent me another Surround EQ card. I set the levels to match the old card.

quote: Darryl Spicer
Does it have the older type format card in it.

It's a JFM-05A, which I'm guessing is old(ish). The surround switch is always on.

So, I've removed the cards (with the power off), cleaned the contacts with a pencil eraser, and reset them firmly in their place. I don't have any Dolby tone loop, however, so testing it on film is going to be tough. Clint, I'll give you a call right now.

Posted by Dan Chilton (Member # 2288) on 01-10-2006, 05:50 PM:

I spoke to my tech, and he suggested I wait until the surrounds are on, and then wiggle the surround EQ and the format card to see which one might be the cause of the problem. Does that seem a bit problematic? Is it okay to wiggle the cards when the processor is powered on? If the surround EQ card comes out, the surrounds will obviously shut off... likewise with the format card. So how does that help me narrow down where the problem is?

Does anyone else have some suggestions?

Posted by Richard Hamilton (Member # 321) on 01-10-2006, 06:05 PM:

I am assuming the problem is still happening. Do you have another unit that you can swap the Format card with?

Rick

Posted by Clint Koch (Member # 1179) on 01-10-2006, 06:14 PM:

Dan, you called and left a message with me yet you did not leave a phone number. I will be in tomorrow and would like to talk to you over the phone. 805-549-0161

Posted by Phil Hill (Member # 371) on 01-10-2006, 06:22 PM:

I'd be careful Dan... I think Clint is hitting on you... [Smile]

Posted by Clint Koch (Member # 1179) on 01-10-2006, 06:45 PM:

Dan and I have spoken and I am leaning towards a flaky power supply. The JPS-05 is a really old power supply that is not even repairable. It needs to be upgraded to a JPS-10 which should resolve the problem. I'll use the analogy of a 8 cylinder car running on 6 cylinders, yes, it will run yet it will not run right. The JPS-05 has a +15 and -15 volt regulators in it and one of these may be getting a bit tired or it may also be the transformer in the JPS-05 that is getting tired. Either way the best test for now is to get a JPS-10 power supply in the unit and let it run for a bit as Dan has already replaced the surround and format cards to no avail. Will let you all know what happens when we get the JPS-10 to him.

Phil, I hardly know him! LOL

Posted by Dan Chilton (Member # 2288) on 01-10-2006, 07:33 PM:

Clint: when we spoke, I was relying on an inventory sheet that I made during booth installation. However, upon further inspection, we DO have the JPS-10, as opposed to the 05 that I mistakenly told you we had. I'll give you another call in the morning before I call the equipment dealer.

Thanks again for all your help!