bobair8(at)msn.com
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 Posted: Tue May 15, 2007 7:21 pm Post subject: Comm and Intercom Interconnection: Expected Results? |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> Hi,
I'm installing a Garmin GNC250XL VFR GPS/Comm and a PS Engineering 1000 II intercom.
I've been checking for opens and shorts between my mic and headphone jacks and the connectors at the end of the harnesses for the Comm and Intercom. (As detailed below, I've installed three sets of jacks in this two-place airplane -- pilot, copilot and aux.)
Is the following behavior to be expected? I don't want to wait until the windshield is in and everything is installed before I find out something is wrong. (The asterisked items show my specific concerns/questions.)
***Mic Tip: Continuity for Pilot's and Aux Mike jacks to correct pin on both Comm and Intercom connectors. The copilot mic tip has continuity to Intercom pin but shows 164 ohms resistance to Comm pin whether PTT button is pushed or not.
***Mic Audio Hi: Continuity for both pilot's and aux mic jacks to both Comm and Intercom. Copilot's mic jack has continuity to Intercom but is "open" to Comm pin.
Mic Audio Lo: All three jacks show continuity to both Comm and Intercom.
***Headphones Tip: Pilot's and copilot's phone jacks show continuity to Intercom but are "open" to Comm. Aux phone jack shows continuity to both Comm and Intercom.
Headphones Ring: All three jacks show continuity to both Comm and Intercom.
Additional details about my installation follow:
The wiring diagram for the Comm shows (numbers in parenthesis are pin numbers on that units connector):
- (4) Mic Key to Mic Jack
- (2) Mic Audio Hi to Mic Jack
- (3) Mic Audio Shield (Low) to Mic Jack
- (5) Comm Audio Hi to Audio Panel
- (6) Comm Audio Low to Audio Panel
The wiring diagram for the Intercom shows:
- (12) Aircraft Radio PTT to Aux Mic Jack
- (25) Aircraft Mic Audio Hi to Aux Mic Jack
- (13) Aircraft Mic Audio Low to Aux Mic Jack
- (17) A/C Radio Phone Audio Hi to Aux Headphone Jack
- (4) A/C Radio Phone Audio Low to Aux Headphone Jack
I've installed an aux mic jack and aux headphone jack in addition to the pilot's and copilot's jacks. I've soldered the wires from both the Comm and the Intercom to their respective points on the aux jacks. That way if my Intercom dies, I can plug directly into the Comm and completely bypass the Intercom. The PTT wires for the Aux Mic Jack run to a two-pin Molex connector just downstream from the pilot's control stick. The respective wires from each of the pilot's and aux jack are crimped into one pin. (I didn't attach the shields together here to avoid a ground loop. Shields are connected together elsewhere.)
I'm also using two conductor 22 AWG shielded wire and am using the shield for the "Lo" conductor.
Thanks in advance.
Best regards,
Bob
GlaStar
N248BF
[quote][b]
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