Kinoton FP25D random sound distortion

[Steve Pike]

Hey all

So, random one - I just tested a short reel of ads and trails plus the first part of a feature film ready for my first screening to family and friends on Friday in the home cinema (now that we can have them inside thanks to some covid restrictions being lifted in England).

Strange thing happened tonight, which has never happened before.

Firstly, ran the same set of ads and trailers the other day and no issues.

But tonight, ran the the ads and trails as I’ve now made up the feature film which is attached to it. Everything ran with perfect sound, then a join went through after a “no smoking” ident into a ident for “feature presentation” and suddenly the sound was distorted and “warbling” a bit. This then had a knock on effect to the sound start of the feature film which is attached to the end of this ident which continued with this distorted/warble sound.

There was a click when the join went through the projector (not like the normal join sound) which I wasn’t sure if that was causing it.

I reran the reel again, and it kept doing the same thing at the same point. Which I thought was weird. Bearing in mind earlier in the week it was fine!

Here is a link to a video - hopefully you can hear the weird sound on the Feature Presentation ident. The audio on the Orange (Dennis Hopper) and No Smoking is clear. Then the audio on Feature Presentation is not right.

So, it tried the following;

- reduced the skate slightly
- respliced the join between the “no smoking” ident and the “feature presentation” ident

I then ran the film again and this seemed to sort it, but it’s puzzled me as to why it’s suddenly happening - at the same point.

Could it literally have been a bad join that caused this?

anyone ever had this or have any other suggestions?

thanks in advance!
steve

[Phillip Grace]

The effect you are hearing is known as "Flutter".
Got a couple of questions. Are you replaying analogue or digital sound? Have you observed the film motion around the soundhead when problem happens?
And a couple of suggestions. Kinoton soundheads have very little positive control of the film as it passes through them. The "O" rings on the lay-on roller must be in good condition and clean at all times. The spring tension is also critical. Too little and the lay-on roller will not damp the film motion sufficiently. Too much and the film will veer off to one side of the film path. The condition of the film itself will influence the result. Badly deformed film is likely to cause problems on a Kinoton which might not occur elsewhere. The bearings in the Kinoton lay-on roller must be lubricated with the viscous Kardan Oil as supplied by them. This is where the damping action comes from. A free-spinning lay-on roller will not damp the vibration of the film as it leaves the intermittent sprocket, and the poor film motion will appear at the scanning point.
You mention that the problem is associated with a splice. This may be related to the spring tension of the pad roller/clamp arm associated with the lower feed sprocket. These arms do not lock into position in the conventional sense. They simply rely on spring tension to hold the film to the sprocket, and the springs loose their tension over time. (There is provision to adjust it). This is all fine with new film in good condition. Film with any degree of shrinkage will ride up of the sprocket teeth, and in combination with high take-up tension, might pull over the sprocket one perf at a time until the lower loop has disappeared completely and the sound will flutter as a result. A stiff splice or a splice made out of correct pitch will certainly cause a problem under these circumstances.
A lesser known problem which sounds like flutter can occur with Dolby Digital sound tracks. This is occasionally noticeable at the end of a feature which has had a long run on a platter system, and a badly worn or damaged digital track, where the digital track fails frequently and the processor flips rapidly back and forwards between digital and the analogue back-up.

[Steve Pike]

Hi Phillip - thanks for your response ... some answers below ...

Got a couple of questions. Are you replaying analogue or digital sound?
Playing analogue sound

Have you observed the film motion around the soundhead when problem happens?

Sort of, it looks like the film loops up slightly as it goes past the soundhead - but then seems to settle. However, touching on a point you make further down, when this join goes through you - I heard this click, which may be the lower feed sprockets clamp. What follows immediately is also a sort of 'shunt' sound (sorry, probably a really bad description) - almost like when you have a bit of sticky film that suddenly gets pulled apart as it comes off the pay-off reel and so there's a bit of a jolt with the tension - I'm wondering if that's what's happening with the lower shoe. And it needs to be tightened. Almost like when the join goes through, it's somehow lifting up the shoe and the film is jumping the sprockets. Is that what you are meaning? Plus, I did increase the take-up tension slightly too.

[Phillip Grace]

Hi Steve.
If the film is jumping over the lower sprocket it will eventually shorten the loop of film between the intermittent sprocket and the soundhead to the point that the film is snagging on something and the motion at the soundhead is no longer smooth. This is possible on a Kinoton because of the design of the shoes, where it would not be on other machines. This should be pretty easy to see. If it progresses far enough it will pull the gate open and badly damage the film. Try threading with a larger lower loop to allow a couple of extra perforations margin. If the film is "singing" as it passes over the sprocket this would indicate the take-up tension is too high, and/or the film itself is significantly shrunk, and riding up on the sprocket teeth.
The problem certainly seems to be related to the join disturbing the equilibrium of the system. The Kinoton soundhead is a peculiar beast. It relies very much on the natural compliance of the film when in normal motion, and doesn't have the kind of "grip" on the film as a more conventional arrangement. I have found after years of trying to coax banged-up horrible shrunk prints through them that a combination of factors are in play. Working out exactly what is going wrong involves a lot of observation, and some very cautious methodical adjustment.
Hope this has been some help.

[Steve Pike]

Hi Phillip

I had a look at the shoe today, and tightened it. It seemed to be OK but I did a little adjustment anyway (something like that has never been done on this projector for many years…if at all!).

Re-ran the film today and all seemed well.

Kept and eye on the shoe, and kept checking to see if any joins loosened its grip but all seemed well.

I also reduced the tension for the takeup reel on the tower. Also noticed that the frame knobs centre marking was pointing over to me / operator side. So I put that back up to match the marking on the projector body (i.e blob on the knob is at 12 o clock). I wonder if this was also a cause?

Anyway, ran the reel of ads and trailers - all seemed well, so continued through to reel one and into reel two of the feature and sound was great.

The wife is out on Wednesday so will have a chance to sit and run the whole feature in readiness for the screening on Friday!

The Kinoton system can be a sod at times, unlike other systems … I “cut my teeth” on a Westar/Century projector back in the day and they were amazing.

Thanks for all your help and suggestions, it’s really appreciated

steve

[Stefan Scholz]

According to the manual, you should set the shoe so, that a spring loaded scale that you pull shows around 200 grams when the shoe opens, and around 400 grams when held fully open.
There is a special tool included in the tool and spares kit that came with the projector, that enables you to keep the outer ring tensioned while fixing the center lock screw..
Also the shoe is to be adjusted to have about 2 film thicknesses of clearance. 2 polyestar film pieces on top should pass, a third should lift the shoe.
It's a nasty thing, when the loop gets lost on a bad splice, or by shrunken film. But on the other hand, a well maintained Kinotone offers pristine images, if it is the last generation of the FP series.
Yours is one of those.

[Steve Pike]

Hi Stefan

I do like the description of the 'special tool' which I also saw in the manual, but I do not have one haha. There were lots of things that we were suppose to have with this projector when it was new (when it was first installed at the theatre I work at) but were never passed to us!! So I used a combination of an allen key and flat screwdriver! Seemed to do the trick