Help with SL 30 and Apollo Audio

[F1R]

Gentlemen,

I have an Apollo NAV/Com Stack that used to perform flawlessly.

CD 15, GX60, SL30& SL70 All was fine for about 270 hours. Either radio works fine either TX or receive, without the intercom.

Also the intercom may be on with the radios off and all is silent, volume up or down, normal intercom function.

The problem is that when the SL30 is on and all is normal as soon as the CD15 intercom is turned on, there is deafening static in either headset.

Reducing the radio volume lowers the static however this also reduces any incoming radio voice at the same time. Switching off the intercom restores silence in the radio even with the volume turned way up. Normal transmit and reception is back again.

If anybody can suggest what has changed or what might be done to cure the problem, it would be greatly appreciated.

Thanks in advance,

Richard

 

[chipf]

I had a similar problem on a rental plane recently. Someone had turned up the volume on the NAV identification audio channel. Once I turned that off, all was well.

 

[RV6_flyer]

I hope I understand the problem and do not have you going down a wrong path.

Check the NAV button on the SL30. I have seen a similar issue with the NAV button being on ID or VOICE and forgetting to switch it back to out. If that does not help, tune to a different VOR. Have seen a couple of VORs that was transmitting static or at least my NAV picked up static when I was tuned to it. When you ID a VOR, you need to press the NAV button TWICE to get back so that there is no noise on the NAV radio audio output.

My SL30 was sent to the shop last week 9 years and 2 months to the day after it was installed. It has a COMM only audio distortion. Turn the COMM volume to full volume, and the distortion goes away. IMHO, there is something wrong with the audio amp. The NAV audio works perfect. Yes it is $450 for the repair and it MUST go through a Garmin dealer. (I purchased the GX60 and SL30 from Van's back in 2001.) Use a local dealer for the return.

 

[Bob Axsom]

Well what is with the CD15?

The SL-30 I recently installed is a bit of a pain IFR operationally because of all of the software controlled functionality. It has a very wide range of functionality but I am having to develop procedures to eliminate the "radio operation distraction" when I have to focus on flying the airplane on instruments. I hooked mine up to a Terra audio panel along with a SL-60 and a Terra NAV radio and the fact that I could not get the code from the SL-30 VOR audio when I turned the Terra NAV 1 audio panel switch to headset was a bit depressing. Using the SL-30 Pilot's Operating Manual I found that the "ID" button on the SL-30 controls 3 NAV audio output states. It works fine but it has to be in the right state for the VOR coded identification to be heard.

The way you describe you situation it sounds like your condition exist regardless of any NAV function or state. You may have done this but your description doesn't really state it so I would turn the SL-30 off at the unit and turn of the CD15 (whatever that is - I assume an audio panel) then power up the avionics and turn on the CD15. If there is no noise then the problem is definitly an interaction between the SL-30 and the CD15. Turn on the SL-30 and make sure the squelch is set to squelch the low level noise and only pass good strong receptions. It will probably make no difference but it is a quick check just to fill up the knowledge base. There is a set up mode in the SL-30 that is activated when the power is off, the flip-flop button and the SYS button are held in and the power is turned on. I don't remember if there is any parameter in there that could effect the condition you are experiencing or not - and their are some operational mode adjustments that may effect your problem - you need to look at all of them and do your best - the manual is very superficial so you need to really read between the lines to ferret out the possibilities. I suspect that your problem is somewhere in the interface wiring - shield strands shorting to primary conductors - shielded twisted pairs hooked up backwards - grounding problems, etc.

Good luck with the SL-30 does everything magic box - I'm still trying to get familiar with mine.

Bob Axsom

 

[F1R]

Thanks for the leads. I'll post when I resolve it. Hopefully it is just a finger problem of my own making.

 

[F1R]

Resolved

Thanks RV6 flyer! Evidently I must read that manual. I had tuned a distant VOR a few weeks ago while solo. The readout and CDI worked just fine, however the ident code was not audible over the static when I turned on the intercom a week later. Thanks for joining the dots for me.

Richard