8mm Forum: st 1200 optical sound

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Posted by Chip Gelmini (Member # 44) on September 28, 2003, 02:56 PM:

Could you please tell me about the OPTICAL PREAMP. I am trying to determine if the projector is worth fixing, and what the repair would involve. The projector is an Elmo ST1200D single track mag unit /w/ optical built in. Until now, the unit has always worked very good. I bought the unit new in 1987 and it has never had any other type of repairs beyond bulb changes (lamphouse) and minor tuneups, all of which I have done by myself. Thanks in advance.

ps....I have already looked at the gearbox and checked the fuses. They are OK. I noticed near the elevation knob there is one capacitor or resistor, 2 inches long, maybe 1/2 inch diameter appears to be linked to the optical bulb socket based on following the wires as best that I could. Also checked the amplifier circuit board. Nothing that I could tell seems to be burned out or smoked. No residue or anything like that, and/or bad smells. Everything looks clean. Keep in mind I know NOTHING about cicuit boards or sound reproduction when it gets involved like this. I definately need a technician for this if I am to get it repaired.

Posted by Douglas Meltzer (Member # 28) on September 28, 2003, 05:09 PM:

Chip!
Pardon me for straying from your topic, but I just wanted to welcome you back to the forum. It's nice to see you posting again! If no one here is wise in the ways of the preamp, I'm sure Leon Norris (610-275-1225) would be happy to help.
Doug

Posted by John Whittle (Member # 22) on September 28, 2003, 07:53 PM:

Chip
Is the exciter lamp lighting up? If not you might check the bulb or if this normally only comes on when the projector is in optical you may have nothing more than a dirty or oxidized switch. However to really check it out you nned to use a multimeter and know where to check.

John

Posted by Paul Adsett (Member # 25) on September 28, 2003, 08:17 PM:

Chip,
Welcome back! You have been missed.

Posted by Chip Gelmini (Member # 44) on September 28, 2003, 10:42 PM:

Hi guys. Thanks for your warm wishes. For me it's been a crappy year. I still owe dealers (film, that is) and I want EVERYONE to know I am only asking for insight to this problem. I won't get it fixed until other things are DONE.
Since I referrecened DRUGS, I am being treated for allergies and it has not been fun. I just turned 43, and have had two attacks that sent me to the ER at the local hospital once. The second I was lucky enough to get to my regular DR the same day. It turns out I am addicted to nasal spray, and I am working to get better. Now on Claratin, I am doing better.
I have not done much with super 8, but I am working on a new 35mm to super 8 conversion. Like the scope lens, you'll all be able to do this next thing too. But for the moment I'll keep you wondering what it is. But let me say this. For the recent posts about super 8 and is it doomed......now you can keep wondering what I've got planned. For those of you know how good the scope lens works.........

Thanks again for your nice comments.

Chip G

Posted by Chip Gelmini (Member # 44) on September 29, 2003, 09:35 AM:

The optical light does turn on, and magnetic sound is nice and strong.

chip

Posted by John Whittle (Member # 22) on September 29, 2003, 02:09 PM:

Chip,

Since the exciter lamp lights and the mag sound is good, it's either the solar cell (very unlikly unless physically damaged) or the leads to the amp or the switch and first stage of the amp. Really need a schematic to check this out.

John

Posted by Chip Gelmini (Member # 44) on September 30, 2003, 10:56 AM:

John Whittle:

If the solar cell is damaged, how could that happen? Is it possible the print could have done it? Is the solar cell the glass lens right at the optical bulb, or inside near the sound flywheel roller? The film I ran when this problem developed was a pinkish print (color fade) and whereas the sound seemed abit low overall.

Chip

Posted by John Whittle (Member # 22) on September 30, 2003, 05:30 PM:

The solar cell is inside the flywheel. The exciter lamp, optics, film, solar cell.

Have you tried other prints? One problem with 8mm optical sound is that it is a dye track and as film fades so does the sound. If you have a black and white optical sound print try that. The problem may not be the projector at all.

John

Posted by Kevin Faulkner (Member # 6) on October 05, 2003, 03:53 PM:

Welcome back Chip. Another pos is mag oxide on one of the optical components. Make sure the optical lens is clean at both ends as well as the surface of the solar cell. A can of compressed air is good for this or a cotton bud soaked in isopropyl alchohol.

Kevin.

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