This is topic Eumig Mark S-710D Nothing But Hum -- Last Recourse? in forum 8mm Forum at 8mm Forum.

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Posted by Chad Gayle (Member # 3602) on March 19, 2013, 03:05 PM:
I've got a Eumig S710D that produces a loud buzzing hum with the volume turned all the way up and no sound with the volume turned down.

After scouring the forum for all of the related threads, I tried the following:

1. Exercised red record button many times with projector set to reverse.

2. Checked speaker contacts for corrosion (none).

3. Checked for fuse -- and this is weird: on my unit, there is a spring installed instead of a fuse! As it appears to fit perfectly, I think it was made that way.

4. Tried to exercise DIN output switch in several different ways. No improvement.

5. Tried hooking external guitar amp directly to wires meeting at the back of the DIN switch; amp duplicated same loud hum.

6. Tried moving each of the hum coils slightly with no effect. Mine has a white and a red coil; there is another coil below the sound head.

Following instruction in the Eumig manual, I have tried to pull the sound head out to have a look at it, but on mine, after I get the spring release out of the way, there is a metal bar that blocks removal of the head. I can loosen it enough to peer in with a flashlight, but not much else.

Note that there is NO sound when I turn the volume all the way down, so that seems to rule out any problems with the speaker.

Anyway, I'm just about ready to give up -- unless any of you guys have some ideas??
Posted by Zechariah Sporre (Member # 2358) on March 19, 2013, 09:10 PM:
This is probably a dumb question but did you flip the switch under the front cover close to the sound head for playing super 8 sound or regular 8mm sound films?
Posted by Chad Gayle (Member # 3602) on March 19, 2013, 09:21 PM:
No, not a dumb question -- yes, I forgot to mention that in my list of things that I did. I switched it back and forth from N to S several times to make sure the contacts got some "exercise" -- and the proper S gates are in; switch is set to S.

I'm wondering if maybe the caps are bad? Has anyone had the same issue and fixed the ound by replacing the large caps?
Posted by Bill Brandenstein (Member # 892) on March 20, 2013, 01:32 AM:
Absolutely. I have an 800-series projector that still hums, but was worse before replacing a couple of big caps. Go for it.
Posted by Zechariah Sporre (Member # 2358) on March 20, 2013, 01:02 PM:
I have another dumb question. What parts are you refering to when you say caps?
Posted by Alessandro Machi (Member # 461) on March 20, 2013, 01:24 PM:
Just a shot in the dark. If you have cable, and the cable box is nearby or connected to the same wall outlet, that might create hum as well.

Ideally you would want to find an entire circuit in your residence with nothing hooked up but your projector and see if there is any difference in the level of hum you are having.
Posted by Chad Gayle (Member # 3602) on March 20, 2013, 01:56 PM:
I should clarify: there is NO sound except a loud buzzing hum. However, the hum / buzz disappears when the volume is turned all the way down.

By caps, I meant capacitors.

The machine is far away from any potential electrical disturbance.

I would hate to replace the capacitors, which would take me several hours (between getting them and soldering them in) only to find out that the sound head or something else was bad, so I'm hoping that is my last resort.
Posted by Pasquale DAlessio (Member # 2052) on March 20, 2013, 02:09 PM:
You didn't mention cleaning the volume control? [Confused] [Wink]
Posted by Chad Gayle (Member # 3602) on March 20, 2013, 02:14 PM:
I didn't -- I wiggled the volume control, but I didn't clean it. I'll try that tonight, but I don't think that's a likely issue, since there isn't any "crackle" in the sound. I've dealt with bad pots before in audio equipment, and when they go bad, they usually either introduce a lot of crackle or just die.

But a good suggestion, nonetheless -- thanks.
Posted by Maurizio Di Cintio (Member # 144) on March 20, 2013, 03:50 PM:
Bear in mind a certain amount of hum is inherent with these line of projectors. Also a bad soundhead does not result in increased hum: it just cuts meiddle-high frequencies output before dieing (At which point you get no sound at all).

In my experience, dealing with hum issues has always had to do with moving those coils you mentioned: whan I say moving, I do not mean just touch them and move a little bit, but actually gently forcing them so as to vary their positions as opposed to each other. That usually works. If you want better hum reduction, go for an 824: same sturdy mechanics, same dual format capabilities but better sound quality.
Posted by Chad Gayle (Member # 3602) on March 20, 2013, 04:23 PM:
The problem is that I have no indication, at the moment, that there is any sound being picked up by the sound head -- which is not to say that it is a bad sound head, but simply that the only sound that is produced at all with a sound film in the gate is a very loud buzzing hum.

I have tried adjusting the hum bucking coils without noticing any effect.
Posted by Chad Gayle (Member # 3602) on March 22, 2013, 08:09 PM:
Did some investigating tonight on this and I am posting a new question to a new thread.
Posted by Jean-Marc Toussaint (Member # 270) on March 23, 2013, 04:46 AM:
To check if your soundhead is picking up something, tap very gently on it with the tip of a small screwdriver.
As Maurizio said the cause of hum on Eumigs comes genrally from the coils.
Posted by Chad Gayle (Member # 3602) on March 23, 2013, 09:12 AM:
It's the sound head.
Posted by Robert Blackie (Member # 6597) on September 12, 2018, 01:31 AM:
5 years on but..anyone ever suss this out ?
i have the same PJ with the same issue ?
cheers rob
EDIT its ok fixed with the red record button fix [Big Grin]

open back, spray contact cleaner on the switch on the board that comes from red record button.. press record button a few times.. and it worked.. we have sound.

[ September 12, 2018, 02:47 AM: Message edited by: Robert Blackie ]

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