REFLECTOR: Avionics wiring - SL-30 to GMA 340

[Al Gietzen]

  After completing the Tax Headache, I reread your post on wiring. 

I completed the tax headache also, and am now getting back to wiring.

 

I take it you are getting 100 Ohm when reading resistance from pin 7 to pin
13 thru the SL30. 

Yes; the assumption was that if they are both grnd, then there would be zero
resistance, as there is in my other COM.  But in any case, that issue is
resolved after looking at FIG 8 in the install manual where pins 7 and 13
are tied together.

  

Some additional input I can add is : sometimes they wire the transmit key
directly to the mic ground. YOu don't want that because it will require the
use of one of those ugly aftermarket mike key switches. 

 

I ended up (after double checking with the manufacturer) running my mik-key
thru my stick grip PTT, then to ground. Leaving the connection from
mik-to-mik ground open. That way, the PTT works. 

 

I'm not sure I understand this.  Are you putting the PTT in the circuit
between the SL30 pin 7 and grnd?  I'm guessing that only keys that COM.  If
another COM is selected at the Audio Panel, then what?  Maybe I
misunderstand what you did.

 

I have the PTT in the control handle as well, and it is wired to grnd, a
common aircraft grnd with the freq flip-flop and trim switches.  However,
the Audio panel wiring shows the PTT between the mic tip and sleeve, for
either pilot or co-pilot mic; the sleeve is not aircraft ground
(necessarily).  I have been advised to go in and re-wire the grip switch to
bring out another lead so it can connect across pins 34 and 35 on the GMA
340 (between mic key and sleeve).

Am I missing something here?

 

Thanks for your willingness to help.

 

Al

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