8mm Forum: Where's The Hum Gone?

»	8mm Forum » 8mm Forum » Where's The Hum Gone?

UBBFriend: Email this page to someone!

Author

Topic: Where's The Hum Gone?

Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007

posted July 20, 2014 05:47 AM

Years ago I bought new a Eumig 807D. The hum was very noticeable and the amp didn't have much "punch". For my public shows I bought a Craven amplifier, supposedly with a built-in hum filter.

Yes. It not only amplified the projector's output it also amplified the hum to an unacceptable level.

A year or so later it was replaced for public shows by a Bell & Howell DCR which had enough output and even on maximum there was only a slight trace of hum which was quite acceptable.

Recently I have bought a Eumig 810D HQS [High Quality Sound].

Where's the hum gone? No trace of hum and the amp delivers bags of volume. What have the wizards at Eumig done?

It's a nice kit in a fitted case with separate external speaker and a daylight viewing screen.

--------------------
Maurice

| IP: Logged

David Ollerearnshaw
Phenomenal Film Handler

Posts: 1373
From: Penistone Sheffield UK
Registered: Oct 2012

posted July 20, 2014 06:08 AM

This could be the give-away. High Quality Sound.

Eumig did have a poor reputation for hum, one of the reasons I bought ELMO ST1200 (plus 1200ft spools). With the arrival of the High Quality Sound series the reviews seemed to get better on the sound front.

Currently looking for a standard 8 projector myself.

--------------------
I love the smell of film in the morning.

http://www.thereelimage.co.uk/

| IP: Logged

Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted July 20, 2014 07:35 AM

The Eumig 800 series has absolutely miserable internal grounding. When I was developing my sound system I was measuring the voltage between the chassis and the ground at the outlet of various projectors to figure out how bad the ground loop could be. A couple of Elmo machines were running well under .1V, but my Eumig 800 series was about half a volt.

The thing is this voltage winds up mixed in with the audio signal when you run it out to a well grounded external amplifier and the hum can be awful.

If I remember right the problem came down to the ground line running to the power transformer instead of the the projector chassis and the grounding of the chassis was only as good as the contact at the transformer mounting points.

At the time I griped this publicly and found out I'm not the only one to see it.

I set that machine aside as far as the sound system, but I think a couple of star washers installed between the transformer and frame would really improve that contact.

--------------------
All I ask is a wide screen and a projector to light her by...

| IP: Logged

Andrew Woodcock
Film God

Posts: 7477
From: Manchester Uk
Registered: Aug 2012

posted July 20, 2014 07:53 AM

Unbelievable that even in the era these were made, such a basic design flaw would be overlooked and sent to market. Really poor on Eumig's design and marketing teams behalf. Just as well they got it sorted in the later years or else they would probably have gone out business much sooner than they actually did.

--------------------
"C'mon Baggy..Get with the beat"

| IP: Logged

Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted July 20, 2014 11:18 AM

Kevin F. said he actually got a mild shock off of one of these because this voltage grew so large.

So it isn't just an audio quality issue, but a potential safety issue too.

--------------------
All I ask is a wide screen and a projector to light her by...

| IP: Logged

Brian Fretwell
Phenomenal Film Handler

Posts: 1785
From: London, UK
Registered: Jun 2014

posted July 26, 2014 05:03 AM

I remember my old 710D had two coils mounted on flexible steel arms that were supposed to have been adjusted during manufacture to reduce the hum. They didn't!

| IP: Logged

Rob Young.
Phenomenal Film Handler

Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003

posted July 26, 2014 09:46 AM

Yes, Brian, but if you find a used 710 or 810, it is worth moving those coils to try and reduce the hum.

Often they get moved over the years and you can radically reduce the hum with slight adjustments.

Although it never disappears altogether, as others have pointed out, it was a pretty poor design.

| IP: Logged

Osi Osgood
Film God

Posts: 10204
From: Mountian Home, ID.
Registered: Jul 2005

posted July 26, 2014 12:09 PM

"Where has all the humming gone ...
Long time passing ...
Where has all the humming gone ...
Long time ago ...
Where has all the humming gone ...
Gone with good techs everyone ...
When will it ever run?
When will it ever ... run? "

[Big Grin]

--------------------
"All these moments will be lost in time, just like ... tears, in the rain. "

| IP: Logged

Paul Adsett
Film God

Posts: 5003
From: USA
Registered: Jun 2003

posted July 26, 2014 12:23 PM

He's back! [Big Grin]

--------------------
The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj

| IP: Logged

Osi Osgood
Film God

Posts: 10204
From: Mountian Home, ID.
Registered: Jul 2005

posted July 26, 2014 12:34 PM

Yeah, but I gotta go home, I can't play anymore, the wife calls!

Coming honey!! [Smile]

--------------------
"All these moments will be lost in time, just like ... tears, in the rain. "

| IP: Logged

Graham Ritchie
Film God

Posts: 4001
From: New Zealand
Registered: Feb 2006

posted July 26, 2014 01:41 PM

Don't forget folks, that song has a strong reverence to those that have lost there lives in "war" and should not be altered in any way for humour....Its a song that has certainly stuck in my mind since first hearing it way back in the 60s.

Take the time to watch "Where Have All The Flowers Gone?" sung by Marlene Dietrich live at the Royal Variety Performance 1963...its on you-tube.

Graham.

| IP: Logged

Erik Snel
Junior
Posts: 30
From: Leiden, South Holland, the Netherlands
Registered: Nov 2013

posted January 10, 2015 11:05 AM

i know for a fact that the 60o silent series also have ground problems because the metal of the transformer has current too. i know this because it freakin hurted when i touched it by accident. so this may be helped if i better connect the tranfsormer to the ground point of the power inlet? same goes for the sound models is have [Smile]

--------------------
Erik Snel Eumig Expert
ES Filmtechniek

| IP: Logged

All times are Central

Printer-friendly view of this topic

UBB.classic^TM 6.3.1.2