Film-Tech Forum ARCHIVE: Help With Mod IIB

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Posted by Don Furr (Member # 1469) on 05-21-2004, 09:31 PM:

In a nutshell, dual projector setup, ModIIB processor, distortion in both surrounds. Changed out surround amp...no change. Same distortion from both sound heads. In every case, the first part of the surround passage is clear but the longer the passage last the worst the distortion becomes. In a few seconds the racket is PURE noise. Which card in the ModIIB is the most likely culprit?
Thanks....

Don

Posted by Jack Ondracek (Member # 1466) on 05-22-2004, 02:41 AM:

Have you confirmed this isn't a print problem? Did this happen with the show you ran last week? Your description indicates the problem gets worse with time. If you leave the sound system on overnight... or if you come in and turn it on earlier than you normally would, does the problem start earlier?

I'd want to eliminate the print as a problem first... especially as you're a changeover booth.

Posted by Oscar Neundorfer (Member # 458) on 05-22-2004, 06:29 AM:

Don,

First, since you are in Atlanta, why don't you bring the MOD IIB to our factory Monday morning, and we will attempt to repair while you wait. We are in Norcross. Call 770-449-6698 Monday morning to arrange a time.

You mentioned BOTH surrrounds. The MOD IIB has only one surround output.

Most likely problems would be Matrix card or time delay card. We can supply you with both cards, and you can see which one helps.

Please look at the time delay card and tell me if it has DIP switches or a rotary switch to set the time delay for surrounds. The older style with the DIP switches was prone to drift over time and to become distorted. It had 2 bias adjustments to set the operating point of the time delay chips, and these are fairly critical. They are factory adjust only.

Hope this helps.

Posted by Don Furr (Member # 1469) on 05-22-2004, 07:08 AM:

The problem occurs with any reel, any print.

Oscar, I pass within 2 blocks of your office on Monday morning at 7am. How early can I drop it off? This unit has the dip switches which have always been turned off. This is used in a 23 foot throw screening room. Would it make any difference if I turned on the delay?

Thanks for your help guys [beer]

Don

As a follow-up I did turn on the time delay....no difference. After running another reel this morning it seems that the quieter surround passages seem to pass o.k. It's the louder tracks that seem to go from clear to distorted. If I'm not mistaken I hear some minor cross talk. Hope this helps.

[ 05-22-2004, 08:44 AM: Message edited by: Don Furr ]

Posted by Gordon McLeod (Member # 33) on 05-22-2004, 09:03 AM:

Have you checked the A chain level is it possible that you are overloading the input

Posted by Don Furr (Member # 1469) on 05-22-2004, 09:26 AM:

Hi Gordon......
The chain was set about 1 year ago. Nothings been touched. This problem started out with a crackling noise then got worse with time. All the other channels sound great.

Don

Posted by Oscar Neundorfer (Member # 458) on 05-22-2004, 09:06 PM:

Don,

I am USUALLY in between 6:30 and 7:00 AM most mornings. No guarantees on a Monday morning, but I will try my best to be there by 7.

Call 770-449-6698 and when the night message picks up, dial 304 and see if I pick up. If I don't pick up, just listen to the prompts and press the appropriate number (2 I think) to have me automatically paged.

Or just stop by. If my green Grand Caravan is in the parking lot, I am there. Just press the doorbell button on the front door, and give me a minute to make my way up front. I will have a pot of coffee in the works, as I can't do much without my first cup to brace me.

Based on your later description of the problem, my bet is on the time delay card as the culprit. This is because the problem I previously described with the bias adjustments is usually worse with louder passages.

Hope to see you on Monday.

Posted by Don Furr (Member # 1469) on 05-22-2004, 09:41 PM:

Oscar.........
Thanks a million. That's what I call 5 Star service.
See you Monday morning.

Don

Posted by Michael Schaffer (Member # 1204) on 05-23-2004, 05:34 AM:

Don`t say that lightly. You have no idea how bad the service for the 5Star and associated parts can be. [Big Grin]

Hahahaha.

What I couldn`t figure out about the ModIIB so far - why are there no test points on the preamp card, but those outputs on the back?

Posted by Oscar Neundorfer (Member # 458) on 05-23-2004, 06:34 AM:

Michael,

You can blame the lack of test points on the Chief Engineer. He can be such a dummy at times.

Oh, wait... that would be me.

<...slinks away and hides...>

Posted by Gordon McLeod (Member # 33) on 05-23-2004, 10:05 AM:

Don't hide just blame your predecessor [Smile]

didn't that card evolve from the earlier MOD2 preamp?

Posted by Don Furr (Member # 1469) on 05-26-2004, 06:44 PM:

There is an end to this story.....here it is:
Took the unit to Smart Devices. Oscar hooked it up and really didn't find anything wrong. He cleaned all the edge connectors on the boards and after reinstalling it at the house, it works perfectly!! Thanks Oscar for your help.
I'm back in business. [beer]

Don