8mm Forum: Need optical sound help...

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Posted by John Capazzo (Member # 157) on July 29, 2014, 06:26 PM:

I have an HD M/O but can't get the optical to work. I've taken out the sound drum and cleaned it; replaced the exciter and positioned the drum so it's aligned with the filament on the lamp. I have an original ST 1200 M/O and the optical works fine on that. I've scrutinized the optical area on that machine and made sure everything was exact on the HD as the 1200. It's not the print I've used since I've run it on the 1200 M/O and playback was fine. The magnetic is fine on the HD and since it is, the optical track should be aligned with the main sound head as the magnetic is. Anyone have any thoughts on what I may have missed? Thanks--John

Posted by Jon Addams (Member # 816) on July 29, 2014, 08:21 PM:

Hello John,

I can send you troubleshooting steps along with schematics if that will help you.

Jon

Posted by John Capazzo (Member # 157) on July 30, 2014, 09:19 AM:

Jon,

I already have the service manual for the HD and I've done everything it dictated except removing the main sound head which isn't the problem; unless you're referring to another source?

Thanks

Posted by John Hermes (Member # 1367) on August 02, 2014, 08:41 PM:

John, I have an ST-1200HD M/O TC (telecine). My optical was not working either. I sent it to Leon Norris. I sent him a lot of replacement parts from a parts machine, including a sound lens and solar cell chip. After much troubleshooting, it turned out to be the pre-amp section of the amplifier had gone bad. He replaced the IC or whatever the part was and the sound returned. I've had a sound lens go bad on one of my ST-180 ETC projectors. It became clouded or stained and would not pass light.

My problem now on my ST-1200HD is the sound lens alignment has gotten off and it's tough to realign. The parts are so small and adjustments microscopic in nature. Getting the lens angle correct using the three screws is difficult. Then you have to have the sound lens focused correctly and the exciter lamp lined up perfectly. All this needs to be precisely aligned to get clean, full, undistorted sound. It's so easy on a 16mm projector.

Posted by Josef Grassmann (Member # 378) on August 04, 2014, 01:50 PM:

if exciter lamp is switched on and sound lens clear and in original position and mag. sound playback is good, then 3 faults remain:

1) defective optical preamp, as already mentioned,
2) broken photo sensor, is 0.4mm thick,only and very brittle!!
3) faulty switch,

Hint: Note that voltage to exciter lamp is increased as soon as film transport is turn ON. Bulb gets lighter,easy visible.

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