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Old 06-29-2017, 04:11 PM
AeroDog AeroDog is offline
 
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Location: New London, NC (near Charlotte), Boulder, CO
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Default page 31B-17 step 5

Page 31B-17 step 5 says check for no continuity between the nut on the jack and ground. I had continuity on all. I had assumed that the idea behind the stepped washer was that the smaller OD on the washer would fit inside the hole in the seat ramp, thereby isolating it electrically. Problem is, the hole in the seat ramp is .375 and the smaller OD on the stepped washer is .434. I'm missing something here. Thanks for any advice.

Jerre
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  #2  
Old 06-29-2017, 04:43 PM
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Tony_T Tony_T is offline
 
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AeroDog,
Well, I think I have the answer for you. My plane was an early build and my seat pan was 2009. The jacks installation was shown on 31-10 sheet dated 05/05/09. On that sheet the hole for the Headphone jack is 3/8" and for the D-180 fuselage wiring harness the headset jack was grounded to the seat pan with no insulating washers. The Mic jack was a larger hole and it was insulated from the seat pan.

When I did an upgrade to SV last winter I installed the latest SV wiring harness and found the situation that you describe on page 31B-17. With both the old plans and the new plans on hand it was obvious what was going on so I used a step drill to enlarge the 3/8" holes for the headphone jacks and insulated them per 31B-17.

This was for SV panel and GTR200 radio and if you are installing something different you best check with Van's.
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  #3  
Old 06-29-2017, 04:57 PM
rvbuilder2002 rvbuilder2002 is offline
 
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This was a design change that older fuselage kits wont have incorporated.
Both holes should be sized (or enlarged) for the insulating washers.

Also keep in mind that the continuity check is happening at a point in the plans where the other end of the cable has not been connected to anything yet.
If you have made connections prior to doing the check you might see the jack body connected to ground.
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  #4  
Old 06-29-2017, 06:01 PM
AeroDog AeroDog is offline
 
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Thanks Tony and Scott,

I'm still unsure (one of my natural states) why it would depend on which SV panel and radio I'm using. I'll be using the SV HDX with whatever the latest and greatest radio is, presumably the GTR-200. Thanks again.

Jerre
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  #5  
Old 06-29-2017, 07:22 PM
Mich48041 Mich48041 is offline
 
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Quote:
I'm still unsure (one of my natural states) why it would depend on which SV panel and radio I'm using.
Installing an insulating washer is not dependent on what avionics are installed. The audio system might work fine without the insulating washer. Then again, it might not. Best practice is to insulate the headphone jack from local ground. When both ends of the coax are connected, the headphone jack will have continuity to ground because the other end of the coax is grounded at the instrument panel. Grounding coax only at one end prevents ground loops. There are exceptions. Follow manufactures recommendations.
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