8mm Forum: Braun visacustic earthing

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Posted by Jose Artiles (Member # 471) on September 06, 2017, 01:46 PM:

I have a Braun visacustic 1000 that have a plug outside, on the projector chassis for earthing,,can someone tell me how i can proceed to do the earthing please?
Thanks in advance friends!

Posted by Steve Klare (Member # 12) on September 06, 2017, 02:40 PM:

It looks like this is an interesting one:

Visacustic Grounding: towards the end of the first post

I guess they were trying to avoid ground loops by offering the user the ability to connect ground as they saw fit

I don't like the idea of operating this kind of equipment ungrounded (been shocked a few times...professional liability!).

If it were me I'd ground that banana jack and bust the ground loops some other way. You'd probably need to make a special cable.

It could be worse: my Eumig 800 series has the three prong power inlet but came with a two prong line cord. I guess the idea there was just float the machine and ground it thorough other connected equipment...or the customer!

(I fixed this.)

Posted by Renzo Dal Bo (Member # 5688) on September 07, 2017, 03:47 AM:

Hi
from the Visacustic user manual:

Posted by Maurice Leakey (Member # 916) on September 07, 2017, 06:27 AM:

Well.
I'm still alive after using my Braun Visacustic 1000 Stereo after nine years, and only connecting to the 2-pin plug with a standard "kettle" lead.
And, no earthing. [Smile]

Posted by Andrew Woodcock (Member # 3260) on September 07, 2017, 06:31 AM:

I think the standard mains IEC plug, lead and socket provide more than adequate earthing for the projector itself.
I would be most surprised if Braun themselves did not use the earth terminal provision on the IEC socket to chassis for the machine itself.

It would appear this is just an additional measure to reduce hum possibly only experienced when the projector is connected to other audio equipment just to reduce any unnecessary hum through the loudspeaker(s).

What I find a little odd about this particular machine, is it is a full true Stereo model yet was only ever supplied originally with one speaker. [Confused]

Posted by Steve Klare (Member # 12) on September 07, 2017, 06:41 AM:

To me it looks like there is no ground through the mains plug, as it says in the post I referenced.

Is it safe to operate the machine ungrounded? Probably. It would be safer to ground it, though.

There's a lot of older machines than this one with metal chassis without any grounding at all. Just like if you take a seat at the wheel of many classic cars there are no seatbelts (never mind airbags).

Your chances of coming out OK are still good in either case, just a lot better with grounded line cords or seatbelts and airbags.

Does this machine have some kind of safety agency mark of it? It just may be double insulated, which would make operating it without the third prong OK. If it has this it's the only projector I ever heard of that does. (This is something usually associated with corded power tools.)

Posted by Andrew Woodcock (Member # 3260) on September 07, 2017, 06:45 AM:

This is very modern machine by Super 8mm standards so despite it's all plastic exterior (double insulated), I have never seen any other similar models without the earth terminal used from the IEC mains inlet socket.

Stuart Reid also has one of these machines so I will check with him how the actual mains socket appears and is connected on these models.

Posted by Steve Klare (Member # 12) on September 07, 2017, 06:48 AM:

A plastic case helps. Many double insulated appliances have this.

It also looks like the supplied inlet is 3 prong, but the original supplied cord is two (like my Eumig).

If the third inlet prong is grounded (and it should be), you could ground the machine by subbing a standard IEC power cord. This is what I did with my Eumig machine.

Posted by Maurice Leakey (Member # 916) on September 07, 2017, 06:58 AM:

The projector only has two pins on its mains input plug. I thought I had made this quite clear.
It does, of course. accept the 3-pin socket on the end of the mains lead, but there is no pin for the earth connection.

Posted by Andrew Woodcock (Member # 3260) on September 07, 2017, 07:03 AM:

That is really unusual then Maurice and thank you for clarification with this.

I cannot for the life of me understand the mindset of the design regarding this appliance then, especially given the era these were made. [Wink]

I cannot think of one similar machine that utilizes this arrangement or any advantages from doing so. [Confused]

Maybe it has an all rubber transformer including it's windings! [Big Grin]

If it were mine, I would place a standard connected socket to it and earth it back to the chassis and transformer just to feel safe using it as these things age.
You never want to risk giving any electrical apparatus the easiest path to earth through the water in your body!

Posted by Steve Klare (Member # 12) on September 07, 2017, 08:04 AM:

Not just water, salt water!

Most of us don't have that kind of musical talent, but at least electrically we are all good conductors!

I can't help but think a reputable company like this went the double-insulated route, and that would include how the transformer is constructed too.

Grounding and audio is a major pain in the butt. This is a creative way to deal with it, to say the least.

It's interesting: I visited my own Eumig 800 series this morning on the way to work, and saw there is no Underwriters' Laboratory mark on the label. I'm betting with a metal case and a two prong cord, they couldn't get the cert.

Posted by Andrew Woodcock (Member # 3260) on September 07, 2017, 08:29 AM:

Yes i'm sure you are quite correct Steve, an attempt to combat the dreaded ground hum issue quite prevalent on smaller bodied machines where the transformer cannot be fitted far enough away really, by attempting this double insulated method of approach again.
i cannot say i am a fan especially as our machines reach old age and if it were my own i would be exchanging that two pin IEC socket for a standard three pin arrangement in a heartbeat!

I'd leave the existing one as is (earth socket) as it is as it is probably routed more directly to the amplifier section and just route some earth flex from the IEC socket terminal to two mounting points on the internal metal chasis at suitable points, one being the transformer and perhaps the motor body also depending on the voltage supplied to it.

Posted by Stuart Reid (Member # 1460) on September 07, 2017, 08:41 AM:

Bang on Andrew, excellent belt and braces approach to stop you bracing for a belt! [Big Grin]

Posted by Steve Klare (Member # 12) on September 07, 2017, 08:44 AM:

I'd almost have to go three prong: I'm a member of the electrical safety committee at work! Being electrocuted would be not only deadly but embarrassing!

Actually the ground loop issue and the internal hum issue are different. The ground loops we usually fight are caused mostly outside the audio components and mostly from voltages induced on the ground conductor by the currents in the hot and neutral wires inside the building wiring. Internal hum is stuff like supply ripple and pickup by the sound heads (you can have a local ground loop inside the projector too).

This is why hum problems can be perplexing to fix: You can have them both, fix either one and still have hum from the other. It's tempting to give up even though you are actually halfway there.

Posted by Andrew Woodcock (Member # 3260) on September 07, 2017, 09:47 AM:

It may very well be trade off by permanently earthing this projector but so long as hum during ordinary playback isn't excessive after doing so, I personally would rather live with that as opposed to handling something that could potentially leave me not watching any films at all in the future! [Wink]

This arrangement could be trialed first without disrupting any of the current set up regarding the IEC socket.

Posted by Steve Klare (Member # 12) on September 07, 2017, 10:37 AM:

True,

The machine could be grounded to the outlet through the banana jack first.

My Amp has a similar arrangement: two prong mains lead and a ground lug on the chassis. I don't use it though. Ground there is through RCA cables to my TV, then through coax to my cable TV provider. (Grounding gets ugly sometimes...) This is why I need ground loop isolation to my cinema setup: it's just plugged into house current and grounded to the water pipes.

-I actually measured 3 volts between these two "grounds" once!

Posted by Andrew Woodcock (Member # 3260) on September 07, 2017, 04:08 PM:

Not bad Steve for something where there should be no real potential difference when you measure across them all! [Big Grin]

Posted by Steve Klare (Member # 12) on September 07, 2017, 05:17 PM:

Should be for certain. Unfortunately it's closely bundled with other wires and their magnetic fields give you kind of an unwanted transformer with the ground wire being the secondary. (I think the major culprit my case is the cable TV system.)

For what grounding is really meant to do, this is no big deal: human contact becomes dangerous above 60 volts. What's a few volts among friends by this standard?

-but then we start mixing line level audio into this mess: a great big 1V RMS signal.

No wonder things hum!

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