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Richard:: Just a starting point: It sounds to me like the wires on the mike input to the KY-97 might have the Push to talk line either grounded, or shorted to the mike audio line. On some of the older transceivers there is a voltage present on the PTT line to energize either a carbon (Lip mike) or an electret mike such as found in the David Clark Headsets, necessitating an isolation resistor to keep the voltage on the PTT line at about 1 volt above ground when the PTT is activated. This is a very low current source so about 1, 000 ohms should suffice. Headset audio in the Narco radios is considerably lower (50 milliwatts) compared to the 100 -250 milliwatt output of the King stuff. Both brands use 4 ohm speaker outputs. The reason for the switch is to turn on the external amplifier in the audio panel for the Narco Radio, while the King radios have an internal amplifier for speaker output, and must be padded down to the Narco level. Kinda complicated, but some Avionics Techs have built careers out of figuring out audio distribution in aircraft with mixed brand, and radio configurations. Maybe this will help, maybe it won't, but it was worth a chance! Good luck Wayne [EMAIL PROTECTED] wrote: > ----[Please read http://ercoupers.com/disclaimer.htm before following > any advice in this forum.]---- > > I just installed a Ky-97A in 99904. It replaced a King 150B that was > installed in 1968. The Coupe has another Com unit (COM 120). It also > has an ADF, Narco Nav unit, transponder all running through a King 20 > audio panel. It has had a switch mark "Speaker" that until I > installed the 97A, > I didn't realize that it was a power switch for the audio panel (makes > sense to switch the unit). Before the 97A, all radios worked with > headphones with the "speaker" switch turn off. I only turned on the > "speaker" switch when I wanted to use the aircraft speaker. > > Now the old COM 120 works just like it always had with the audio panel > on or off. The 97A will work only if the audio panel is on (speaker > or headphones). The 97A goes into a transmitter mode if the audio > panel is > > turned off. It is not a problem to run the audio panel all the time, > but the question comes up what do I do if the audio panel goes out. > Today the > COM 120 will work, but I plan on replacing it and the Narco Nav unit > soon. Should the 97A work with the audio panel off? Did I have hook > something up wrong, ground missing, or is the audio panel bad? Any > suggestion would help. > > I had to install the radio myself because I could find no one who > would work on the old Coupe within 200 miles (at an airport I can fly > VFR to). > > Richard. > N99904 > -- Mr. D. Wayne Woollard, CPBE AIM: DWWoollard ICQ: 124132836 "Why fly a Spam can when you can have fun and fly an Ercoupe?" ==^================================================================ This email was sent to: [EMAIL PROTECTED] EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Sid.bAhN69 Or send an email to: [EMAIL PROTECTED] T O P I C A -- Register now to manage your mail! http://www.topica.com/partner/tag02/register ==^================================================================
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