[Info-vax] grounded MMJ cables

Dave Froble davef at tsoft-inc.com
Sun Jul 18 13:59:49 EDT 2021


On 7/18/2021 12:34 PM, Michael Moroney wrote:
> On 7/18/2021 8:50 AM, chris wrote:
>> On 07/18/21 12:08, Phillip Helbig (undress to reply) wrote:
>>> In article<sd10f5$pd6$1 at gioia.aioe.org>, chris
>>> <chris-nospam at tridac.net>  writes:
>>>
>>>> On 07/18/21 09:35, Phillip Helbig (undress to reply) wrote:
>>>>> In article<sd0n91$i5o$1 at tncsrv09.home.tnetconsulting.net>, Grant
>>>>> Taylor
>>>>> <gtaylor at tnetconsulting.net>   writes:
>>>>>
>>>>>> On 7/17/21 11:22 PM, Phillip Helbig (undress to reply) wrote:
>>>>>>> I'm testing out some MMJ cables (useful for console cables) and
>>>>>>> notice that some (all of which are round rather than flat) have an
>>>>>>> additional wire outside of the plug at each end, which looks like it
>>>>>>> might be intended as ground.  What's the purpose of that?
>>>>>>
>>>>>> How long is it?  I'd expect it to be 3-9 inches if it's meant to be a
>>>>>> ground wire that is attached to something else on the chassis.
>>>>>
>>>>> Yes, about 5 inches.  It has an eyelet at the end, so one could
>>>>> connect
>>>>> it to the chassis via a screw.
>>>>>
>>>>>> I would also have significant worries about ground loops and / or
>>>>>> sneak
>>>>>> currents.  Both of which can be quite dangerous from an electrical
>>>>>> and
>>>>>> safety perspective.  As in more amperage than the wire can safely
>>>>>> handle
>>>>>> turning the wire into a heater that can melt insulation and start
>>>>>> fires.
>>>>>
>>>>> But is that an issue when using a console cable?
>>>>
>>>> Not usually from an interference to the cable  point of view and iirc,
>>>> the added wire is at one end only, which would not enable earth loops.
>>>
>>> I have seen those, but the two I checked today have it at both ends.
>>
>> Ok, but the one I have has just one, but maybe that was third party
>> item.
>>
>
> I have never seen anything like that on a DEC MMJ cable.

Any MMJ cables from DEC that I saw were 6 conductor flat cables.  Not 
that I've seen everything on the planet.

Anybody can make cables with MMJ connectors.  I've done many.  Anybody 
can add anything they want.

-- 
David Froble                       Tel: 724-529-0450
Dave Froble Enterprises, Inc.      E-Mail: davef at tsoft-inc.com
DFE Ultralights, Inc.
170 Grimplin Road
Vanderbilt, PA  15486



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