This is topic Strange Eumig incident in forum 8mm Forum at 8mm Forum.


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Posted by Jean-Marc Toussaint (Member # 270) on August 05, 2006, 08:07 AM:
 
I've been trying to revive an 810 over the last few days. I managed to fix all the mechanical parts and got the machine running at the correct speed (hopefully).
But the sound head is completely useless. So I took the assay from a dead 807, drew a sketch of each wire and where it went, and soldered the whole thing to the N/S switch. Got sound. But not the expected one. What I got is either really loud static/larsen noise, or the radio!

Ironically, when I tested it, the song that came from the projector was a famous bluesy number about the closure of local cinemas and how they were being transformed into supermarkets!!!!!

I'm planning to disassemble the switch and remove old soldering material, clean everything and solder back all wires, in hope it will fix the problem.

Anyone ever encountered that kind of issue?
 

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Posted by Osi Osgood (Member # 424) on August 05, 2006, 09:52 AM:
 
Interesting. have a Eumig Mark S (Mag/Optic) that has beautiful optical sound, but the mag heads have a steady "hum" to them, but since I don't use this projector for mags, it's just fine. I have noticed lately, that it starts running a little slower, probably a belt starting to lose it's grip. Do you know of any scources for belts or any nice replacements for belts, (like, from other kinds of machines?)
 

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Posted by Paul Adsett (Member # 25) on August 05, 2006, 10:36 AM:
 
Hi Osi,
that hum you are getting from the mag sound may be due to the hum bucking coil being out of position. Right below the mag sound head is a little copper coil attached to a metal strip. Turn the projector on to the forward with sound position, crank up the volume, and try moving this coil around a bit to minimize the hum.
 

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Posted by Michael De Angelis (Member # 91) on August 05, 2006, 11:53 AM:
 
I agree.
The moving of the coil
will help alleviate the hum,
becuase that noise can be
painful.

A friend (who is now out of 8mm)
eliminated the hum by replicating
the same low base note on his trumpet
for a friend. His friend sampled
the note and created a home made
knotch filter that would select
degrees of the sound and cancel
the hum from the projector.

I don't know how this was accomplished
but as a musician, he was proud of
the results.

For any of the
electronics experts,
on the Forum, this would
be a wonderful project
to create and share
amongst the collectors.

Michael
 

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Posted by Jean-Marc Toussaint (Member # 270) on August 05, 2006, 12:33 PM:
 
I've disassembled the switch, cleaned it, soldered back all amps, coils and head wires... Still nothing (except the radio when I put a metal object close to the switch). Any idea?
 

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Posted by Joerg Niggemann (Member # 611) on August 06, 2006, 02:14 AM:
 
Jean-Marc, did you hear anything when the old sound head was built in? When you say it was useless, what do you mean: worn out or something else?

I don't know the Eumig 810 at all, but the first thing to check was the proper connection of the sound head to the amplifier board and the sound head coil(s) with a multimeter. A simple test could be to disconnect all wires from the soundhead, put the machine into sound playback mode and touch the open cables one by one. You should then find at least one cable which is connected to the amplifier, resulting in a loud hum noise from the speaker when you touch it.

Joerg
 

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Posted by Jean-Marc Toussaint (Member # 270) on August 06, 2006, 03:44 AM:
 
Yup, did that...
 

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Posted by Joerg Niggemann (Member # 611) on August 06, 2006, 04:25 AM:
 
Did you also check the soundhead's ground connection(s)? A broken ground connection could be the reason for radio sound.

Next thing I can imagine is a problem with the soundhead position or insufficient pressure of soundstripe to head gaps...
 

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Posted by Kevin Faulkner (Member # 6) on August 06, 2006, 03:54 PM:
 
That sounds like a bad earth to me or incorrect connections.

BTW guys never put a DC multimeter accross the sound head or erase head connections. The DC current from the mutlimeter can permannetly magnetise the heads. This is the reason why the erase circuit is AC.

JM, if you have done that then I would certainly use a head demagnetiser before running any film through.

Kev.
 

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Posted by Joerg Niggemann (Member # 611) on August 07, 2006, 06:35 AM:
 
JM and Kevin, I agree that demagnetising is a good advice every time you're working close to the head assay (magnetised screwdrivers, ...).

In my (very personal) opinion, checking the coil with a standard multimeter at a DC current less than 1mA doesn't lead to permanent magnetism that could damage existing sound recordings or affect recording/playback quality. In fact, you should'nt use your car battery and a bulb in this case

Any news about the 810?

Joerg
 

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Posted by John Whittle (Member # 22) on August 07, 2006, 09:26 AM:
 

quote:

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I've disassembled the switch, cleaned it, soldered back all amps, coils and head wires... Still nothing (except the radio when I put a metal object close to the switch). Any idea?

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