Film-Tech Forum ARCHIVE: Christie platter center rollers & DTS

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Posted by Mike Blakesley (Member # 26) on 11-03-1999, 06:37 PM:

After reading the platter tweeking tips here, I have a question about the center roller tension spring....in the tips, it says to remove this. I tried that at one point, but then there is not enough tension in the film and it results in speed variations thru the DTS reader. This makes the sound waver in pitch.

I've tried other solutions such as greasing that center roller spring, but within one or two shows, the roller is dragging again. How can I remove that spring, but still have enough tension to make the DTS reader track properly?

I have an AW3 with non-removable brains, if that makes a difference.

PS: Has anyone seen/heard the new DTS logo trailers yet?

Posted by Joe Redifer (Member # 3) on 11-03-1999, 07:19 PM:

DTS is charging for the new trailers and they are not being shipped automatically. I learned this after calling DTS. You might be able to con some free ones out of them, but nobody in their right mind should ever have to pay for them, so I doubt too many people on this planet will ever see it.

As far as the Christie center roller spring, I have found that with it in it will cause the timecode to drop in and out. When this was happening I would pull excess slack (no tension) and the timecode would read perfectly. So having the spring out is really advantageous for me.

The DTS is wavering in pitch? I have actually heard this happen before (sounds like wow and flutter) but I was using a Strong platter and not a Christie. And it only happened once. I think that perhaps something is wrong with the DTS unit, as it should not do this. If the film is running through at 30 frames per second (just for example) on a 24 fps movie, it should not even attempt to play. Anyone from DTS care to respond to this?

What you can do for tension on the DTS drum is take some industrial strength "paper towels" (I forget the brand that Brad uses) and tape it so the DTS reader drags against it a little bit. I have never needed to do this, but Brad does this, so perhaps he can shed a bit more light on the subject.

Posted by Jim Ziegler (Member # 86) on 11-04-1999, 03:48 AM:

I have started removing the center springs in the brians, and have so far had no problems, DTS or otherwise.

Posted by Brad Miller (Member # 2) on 11-04-1999, 04:54 AM:

Mike, the problem you are having is one (or even all 3) of the brain rollers are damaged and wobbling. Take a look when it is running and you will see the rollers wobble as they turn. That is your problem. You must replace them and tell your guys to BE CAREFUL with those film clamps, as one good hit will do that.

If you look at the UA Galaxy pics in the warehouse, you will see a white piece of folded over "Value Choice" wipers stuck behind the main drive roller and taped down on the backside of the reader. The thickness should be played with on the bench so that there is a definite drag to the roller, but by no means will it be tight enough so it will freeze. This is a one time thing and then you simply remount it to the bracket and let those rollers bounce and wobble all they want from that point on. The DTS will track smooth due to the drag.

Another problem with DTS "wowing" is people who mount an DTS reader on top of an SDDS reader. The SDDS reader has a "bouncing" roller that wreaks havoc on the DTS unit! It can cause all sorts of dropouts and the "wow" you describe. If you theater has done this, simply reset the timecode delay to bypass that SDDS reader straight down (through the 70mm rollers). Alternatively, flip the DTS readers upside down as I have in the UA Galaxy pics so that the "bouncing" roller on the SDDS is completely bypassed, but both penthouse readers are threaded. The latter is my preference.

Note: For theaters with all 3 flavors of digital penthouses, setting them up as seen in the UA Galaxy pics will allow all 3 to be threaded at the same time, even on a 70mm projector with magnetic penthouse, as the stretch of film is substantially less through the readers when set up this way. TRIPLE BACKUP SOUND!!! Also, two DTS 70mm readers can be mounted in typical "forward scan" configuration on top of the SRD reader and threaded straight down...and even those will have enough delay too!

Posted by Scott Norwood (Member # 30) on 11-04-1999, 07:33 AM:

Dumb question regarding digital/mag penthouses: do you have to remove the DTS/SDDS/SR-D penthouses when running 70mm? Or can the film be threaded around them? (Obviously DTS-70 would require replacing the DTS unit...)

Posted by Mike Blakesley (Member # 26) on 11-04-1999, 12:28 PM:

Thanks Brad for the tips, I'll check those out tonight.

I also had a discussion with my service tech about the DTS problem I was having a couple weeks ago, where the UltraStereo processor would kick into "digital" on a timecoded trailer, even though that trailer's sound wasn't on the DTS disk. He thinks the problem could be that DTS is re-using old serial numbers on new trailers. The machine recognizes the serial number and switches to digital, but the machine doesn't "know" that there's no actual sound there....it just looks for the serial number...so it doesn't default back to analog. He is going to check with DTS. Sounds like a good guess to me, but the irritating thing is it doesn't do it all the time. (If I'm standing next to the damn thing, it works perfectly every time!?)

On those DTS trailers, my service guy is selling them for $40 for four (two flat, two scope). Has anybody else paid for them, and what kind of price are you getting?

Posted by Brad Miller (Member # 2) on 11-04-1999, 02:24 PM:

No, you don't have to remove any of the digital penthouses to run 70mm. The 35mm runs down the right side of the penthouses and the 70mm runs down the left side of the penthouses. Nothing needs to be removed or changed when set up in that manner. It is the only way to do it on a 70mm machine to be able to run EVERY possible format.

$10/each for the DTS trailers doesn't sound too bad, but if they want their product to continue to thrive, they'd better start giving those out. Sony charges some ridiculous $30-40 per logo trailer.

Posted by Joe Redifer (Member # 3) on 11-04-1999, 03:45 PM:

I just have to mention this:

Back when I worked for UA and we had SDDS galore, I was told to call Sony and order more SDDS logo trailers. The lady told me that they were $90 EACH! This was when only the original SDDS trailer was available. I told her "$90? I don't think so!" Then she said "Well I can probably get them to you for $80 each". I told her that I needed 4 scope and 4 flat. We continued to haggle prices until I told her that I was only allowed to spend $80, so she sent all of them for $10 each!