Film-Tech Forum ARCHIVE: Eiki RT-0 - Azmuth/exciter bulb

This is topic Eiki RT-0 - Azmuth/exciter bulb - sound problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Brett Bonner (Member # 10378) on 02-27-2018, 10:37 AM:

I began having sound problems on my Eiki a few months ago. I cleaned everything well and all seemed OK but it didn't last. And this time cleaning did not help. I decided perhaps my exciter bulb was going bad and replaced it. In doing so I moved my azmuth lens. Now I can't seem to get a clear sound again. Is there any way to correctly align the azmuth without special equipment? I can get some degree of sound but it is very muddy and at very low levels.
From my understanding the lens needs to be close to the film and the light should exit the lens horizontally correct?
Anyone have any advice? Would be greatly appreciated!

Posted by Scott Norwood (Member # 30) on 02-27-2018, 11:16 AM:

The lens needs to be clean and focused properly on the film (so that you see a clear horizontal line on the soundtrack area). Most Eikis have an adjustment screw to control the lateral position of the lens, too. The exciter lamp itself shouldn't matter much unless the filament has sagged significantly.

In total, you have three adjustments (focus, azimuth, lateral position). Without any test films, you will need to play a film that you know has a good soundtrack and adjust all three factors to obtain the clearest possible sound with the most high-frequency information and without noise from scanning the image area or the edge of the film.

Note that 16mm films usually have the emulsion side towards the lamp (as with 35mm), but some may have the emulsion side towards the lens. This will affect the proper sound focus adjustment. Whatever you are using for a test film should have the emulsion towards the lamp unless you have a large number of films with the reverse orientation.

Posted by Brett Bonner (Member # 10378) on 02-27-2018, 03:52 PM:

Thanks. I think the lateral screw may be part of my problem.
How close should the lens be set to the film?
Does the photo cell need to be cleaned too?

Posted by Gary A. Hoselton (Member # 3447) on 02-27-2018, 06:07 PM:

When sound drops off, it is almost always a sagging filament in the exciter lamp which is no longer in front of the slit lens. Wish they had a height adjustment for the exciter lamp. Never mess with the slit lens, else you have to align it, which you are up against now.

Keep your eye out for the 16mm SMPTE "Jiffy" test film, P16-PP or PPC about 5 minutes long. It contains tests for about everything in the projector, and you can cut out the parts of the sound head alignment you need and make a loops, then replace when done. The slit lens is focused for sharpest sound and the most high frequencies, so move it in and out till you find the sweet spot. You also have to rotate it in azimuth (use azimuth part of Jiffy), and may have to move film sideways to center track in light beam (use buzz track portion of Jiffy test film).

The 35mm Jiffy test film is about twice as long, because it tests stereo in projector and around the auditorium.

Posted by Scott Norwood (Member # 30) on 02-28-2018, 09:25 AM:

The solar cell needs to be clean, but these can be fragile. Just blowing the dust off of it with a can of air should be sufficient. Do not use lens cleaner or anything else.

As for the focus adjustment: you want to focus a sharp line on the film. This is accomplished by moving the sound lens closer to and farther away from the film. You can get this in the ballpark by eye, but you really need to listen to (or measure with test equipment) the output in order to get the adjustment right. An out-of-focus sound lens will reduce high-frequency response.

The lateral adjustment is needed to avoid scanning the picture area or outer edge of the film. Generally, this can be set to whatever gives the maximum volume level without extraneous noise or distortion. This may need to be adjusted for old, shrunken prints.

The azimuth adjustment (twisting the lens) will affect HF response and also the "muddiness" of the sound.

Posted by Gordon McLeod (Member # 33) on 02-28-2018, 10:07 AM:

The lens (optical slit) must be focused to as thin of line as possible as it and the azimuth (rotation) will determin the high frequency output
generally it is best with a high frequency tone loop and one adjusts to get maximum output
It is rarely on 16mm a sagging filament as they are too short in length

Posted by Rick Raskin (Member # 1561) on 02-28-2018, 04:35 PM:

Quick and dirty: Place film in the projector as tightly as possible around the sound drum. Focus the light to as thin a line as possible on the soundtrack as stated above. Then align the beam as close to perpendicular (90 degrees) to the film edge as possible. While not perfect it should get you well within the ballpark.

Posted by Gary A. Hoselton (Member # 3447) on 02-28-2018, 11:55 PM:

Tried to improve my earlier post, but time to edit had passed. Here it is:

When sound drops off with a solid state amplifier, it is almost always the filament in the exciter lamp has sagged and is no longer in front of the slit lens. Happens every 5-10 years in my B&H 2592's. Wish they had a height adjustment for the exciter lamp. Never mess with the slit lens, else you have to align it, which you are up against now.

Keep your eye out for the 16mm SMPTE "Jiffy" test film, P16-PP or PPC about 5 minutes long. It contains tests for about everything in the projector, and you can cut out the parts of the sound head alignment you need and make a loops, then replace when done. The slit lens is focused for sharpest sound and the most high frequencies, so move it in and out and rotate it till you find the sweet spot. The Jiffy focus film has emulsion first on one side and then the other, so can focus half way thru the film and get same results whichever side the emulsion is on, which won't yield quite the best high frequency response but we do encounter emulsion on opposite side of filmbase now and again. You also have to rotate the slit lens in azimuth (use azimuth part of Jiffy), and may have to move film sideways to center track in light beam (use buzz track portion of Jiffy test film).

The 35mm Jiffy test film run time is about twice as long, because it tests stereo in projector and around the auditorium.