Film-Tech Forum ARCHIVE: Frequent soundhead misalignment, RSTR2000

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Posted by Ryan Navaroli (Member # 3477) on 10-13-2008, 09:45 PM:

Hello all. We have 11 screens with Bay Area Cinema Products RSTR-2000 reverse soundtrack readers for the analog sound head on each.

It seems that way too frequently these sound heads will be thrown out of alignment. There are even a few houses where it seems they are being thrown off every couple of months. We currently do not do A-chains or B-chains ourselves, they are preformed by our maintenance group that comes out every 4-6 months. In the time between we seem to just align both parts as well as possible and make the sound as good as possible by adjusting the reverse head and trying to reposition the led.

I guess my real question is, why are these messing up so often? Also, is there any good way to aligning aside from getting an oscilloscope? Any other advice on these sounds head would be helpful as 6 of our 11 houses are SR only while the other 5 have DTS as well.

Thanks in advance.

Posted by Jim Cassedy (Member # 4115) on 10-13-2008, 10:08 PM:

What type of sound-head are the RSTR readers mounted in?
I had a similar prolbem in a couple of auditoriums where I had RSTR readers installed in old SH-1000 soundheads.

I found that the clamp that holds the "reader" half of the RSTR (not the "LED" half) were for some reason not able to securely clamp down on the long cylinder that replaces the old exciter lamp lens slit/tube and holds the electronics in place.

It's like the old clamp in the SH-1000 was slightly oversize by a few 1000th's of an inch. If someone bumped the RSTR tube while threading or cleaning the sound-head it would knock it out of alignment. This happend every few months until I found the cause of the problem.

Solved the problem by removing the unit and wraping a small piece of splicing tape around the tube.

Yes, it IS sort of possible to get a passible alignment without an O-Scope, if you know what you are doing.

I've done this once or twice, using a pink noise and L/R sound loops as as a "quickie" fix, but it's always best done with the proper equipment to get 100% performance out of the reader and your sound system.

Posted by Mark Gulbrandsen (Member # 72) on 10-14-2008, 08:18 AM:

Ryan... Hopefully you don't also have those Chineese projectors! We need to know exactly what it is you have there...

Jim,

There is a tiny bit of difference between the hole size for the old B&L slit lenses vs. the Japaneese slit lenses. I think the BACP is the same diameter as the Japaneese lens but Sam would have to confirm that. Sometimes what happens is the die casting actually stretches a bit and distorto... it can usually be corrected. Take the lens clamp assy out and remove the clamping screw. Carefully get a needle file in between the clamping tabs and file it back open just enough to provide a little extra bit of clamping pressure. Be extremely careful when doing this or the tabs may break off... this is a cheapo, very old die casting! If you break it a new one will have to be installed. The lateral guide arm die casting in same sound head also likes to crack and then the lateral guide ends up at a slight angle ... sometimes the film literally walks right out of the scanner!

Mark

Posted by Ryan Navaroli (Member # 3477) on 10-14-2008, 04:55 PM:

A little more info on the equipment

Our theater was built 3 years ago by the way.
Simplex Projectors
JSD-80 Processor

Jim, I am not sure by what you mean what sound head is it mounted in... I thought the sound head was the sound reader but I am obviously wrong.

Posted by Brad Miller (Member # 2) on 10-14-2008, 05:23 PM:

This is certainly not the fault of the BACP reader. Either things are not getting properly tightened down after the alignment, or you've got an issue already explained above.

Posted by Sam D. Chavez (Member # 1841) on 10-14-2008, 11:08 PM:

Hello from Show East.

Can you clarify what you mean by needing alignment? Do you pick up sprocket holes, frame line noise or DTS time code in the sound, or does the sound go out of focus and lose high frequency response?

The readers don't normally drift, but the position of the film can certainly change position relative to the reader lens for a number of mechanical reasons.

We are all here to help you but you need to provide more detailed info so we can make better suggestions.

Posted by Ryan Navaroli (Member # 3477) on 10-16-2008, 07:01 PM:

Sam and everyone else,

My apologies for the short-sightedness in not describing the problem better.

Most frequently the sound we begin to muffle and get quiet. Also, in one theater now the high-frequencies seem to hiss. On occasion we have had the motor boat sound but I think that was lateral guide issues... can't remember.

I do not know about picking up extraneous noises like sprocket holes or DTS code and can't imagine what frame line noise would sound like. It seems all of these would be very apparent especially sprocket holes producing a rhythmic sound?

Oh well lets see if that helps at all.

Posted by Louis Bornwasser (Member # 3063) on 10-16-2008, 08:35 PM:

OLDER Simplex will have issues with the clamping mechanism being oversized OR BROKEN. The only other fault is that 93% of the lateral guide arms were manufactured with a hairline fracture; this causes unstable alignment or the end actually drops off. (Newer Simplex appears not to have this problem.)

There is nothing about the Bay Area unit that is unstable.

We find alignment holds for YEARS. Only the LED will show drop-in-level over the years. Louis

Posted by Demetris Thoupis (Member # 833) on 10-17-2008, 02:00 AM:

When the sound gets low and muffled did you check to see whether the two green level LEDS on the BACP unit blink quite brightly or do they blink dim? If the blink bright and still you have low and muffled sound then there is something wrong with your processor. At least you can start eliminating the great BACP readers as I personally never had any issues with them. They are great, track excellent and are a piece of cake to install in comparison with other companies' readers.
In any case, when we did an install with an DTS XD10P unit (its like the JSD80 unit), I had some strange problems with high frequencies suddenly noising in various channels and had a small muffle in the centre channel. I did a firmware update and all seemed to vanish. Perhaps that is what your technician needs to do first. Clint might be able to poke in and mentioned the latest working firmware that you should have on your processors.
Demetris