ctfarmer Posted April 15, 2017 Report Share Posted April 15, 2017 I have a Garmin SL40 and has just experienced the following problem. During a flight, the Tx stopped working but the panel still displayed the dual frequencies. Prior to this issue the unit was working normally. I terminated the flight and started to troubleshoot on the ground. The following symptoms are evident. · Turn the power on using the circuit breaker or avionics switch and the dual frequencies display for about 1-3 seconds then fade or flash quickly away to nothing. · During the 3 seconds, the Tx appears to work until the unit goes off. · Once off as above, the unit has no working functions. · With power on the unit, using the units on/off control knob and nothing shows - the unit doesn’t turn on at all. · the head phones plugged in or unplugged, have no affect on the operation as above. I have measured 12+VDC on pin 1 on the RS232 connector on the cassette mounting plate. I have negligible resistance to the ground/earth on Pin 9 (power earth) back to the busbar located on the passenger side firewall in the cabin. I have not checked the resistance from there to the battery negative terminal but did tighten up the bolts. Everything else works fine connected to that ground busbar and will check further tomorrow. I suspect a ground or power issue but on the basis of the tests i have done, everything looks fine. I will set up a 3-4 amp load and load test from pin 1 to pin 9 measuring voltage at the same time. Anyone got any thoughts. Quote Link to comment Share on other sites More sharing options...
CT4ME Posted April 15, 2017 Report Share Posted April 15, 2017 Check all grounds. And make double-sure it is seated fully in the receiver, so that the connector is all the way in. Quote Link to comment Share on other sites More sharing options...
ctfarmer Posted April 16, 2017 Author Report Share Posted April 16, 2017 Grounds were all fine. Was able to borrow the same radio from another aircraft. No problem with it in my cradle. Opened mine and it smelled slightly of burnt electronics. One cap is clearly cooked. Very odd. Quote Link to comment Share on other sites More sharing options...
ctfarmer Posted June 10, 2017 Author Report Share Posted June 10, 2017 SL-40 failed internally with over voltage to part of the circuit. Not reparable. Installed a new Icom A220 radio. Looks to be, on the surface, far better made and engineered. However, for the entire duration of my first flight, i had what appeared to be a squelch problem - could not be set to overcome noise. Turned out to be a 12V to USB socket adapter i had running my Ipad plugged in in close proximity to the radio. Easy fix once i found the cause and it is a much nicer unit to operate. As well, looking at its design and manufacture, the cast aluminium chassis for example and general feel of knobs, i have far greater expectation it will be more robust electronically. Quote Link to comment Share on other sites More sharing options...
Anticept Posted June 10, 2017 Report Share Posted June 10, 2017 Not repairable? That's really strange for garmin to do that on an aviation unit! Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted June 12, 2017 Report Share Posted June 12, 2017 Seems unusual, in my neck of the woods the SL30/40 radios have a great reputation for reliability. Good luck with the Icom, those radios look very nice indeed. Quote Link to comment Share on other sites More sharing options...
Snoopyeagle Posted June 13, 2017 Report Share Posted June 13, 2017 I pulled out a SL-40 Last week from my CTSW because here in the UK we all have to have 8.33Khz spacing and I installed a Icom 220 and agree with Ctfarmer it does look and feel a lot more robust, I haven't flown it yet but my iPad is plugged in via a USB port next to the radio so I will listen out for the squelch problem. I now do have a working Garmin SL-40 if anyone wants one as it is of no use to anyone in Europe now. Quote Link to comment Share on other sites More sharing options...
Runtoeat Posted June 14, 2017 Report Share Posted June 14, 2017 Snoopyeagle, please send me a email regarding your SL40. reh3335@yahoo.com Quote Link to comment Share on other sites More sharing options...
cgrbu Posted July 26, 2017 Report Share Posted July 26, 2017 To add my situation to problems with the Garmin SL-40, on my last two flights I have got a lot of background static/noise when I transmit. Both push-to-talks on pilot and passenger control sticks have the problem. Other aircraft have confirmed the 'noise' on my transmit. Reception seems okay. Swapped out headsets, Tango to Zulu to DC.... no change in condition. I will try to play with connections in back but I am in the dark... any advice on this would be appreciated... thanks Quote Link to comment Share on other sites More sharing options...
coppercity Posted July 26, 2017 Report Share Posted July 26, 2017 1 hour ago, cgrbu said: To add my situation to problems with the Garmin SL-40, on my last two flights I have got a lot of background static/noise when I transmit. Both push-to-talks on pilot and passenger control sticks have the problem. Other aircraft have confirmed the 'noise' on my transmit. Reception seems okay. Swapped out headsets, Tango to Zulu to DC.... no change in condition. I will try to play with connections in back but Im in the dark... any advice on this would be appreciated... thanks Do you have the Intercom Bypass plugs installed? Have you tried going directly thru them? Quote Link to comment Share on other sites More sharing options...
cgrbu Posted July 27, 2017 Report Share Posted July 27, 2017 I am not sure if the two additional plugs below my PFD Skyview is what you are referring to? Quote Link to comment Share on other sites More sharing options...
cgrbu Posted July 27, 2017 Report Share Posted July 27, 2017 I have tried that long ago but not recent...when I did use them it isolated the passenger system... I will give it a go.... also Tom (a.k.a Roger ) Lee has made some good suggestions that I will address this week-end, (gnd, tray and if all fails, bench test) Quote Link to comment Share on other sites More sharing options...
cgrbu Posted July 27, 2017 Report Share Posted July 27, 2017 I have also noticed recently when intercom is on I get a buzzing sound that I think corresponds to the beacon light cycle which is an LED type. I do not notice that when intercom off (no pxx) Quote Link to comment Share on other sites More sharing options...
coppercity Posted July 27, 2017 Report Share Posted July 27, 2017 Is the noise only when the engine is running? If so, while running does the noise go away if you pull the Generator Circuit breaker? Quote Link to comment Share on other sites More sharing options...
cgrbu Posted July 28, 2017 Report Share Posted July 28, 2017 I have not had avionics on without engine running, I will do a static test next and record the results...also will test when running, gen cb out... Quote Link to comment Share on other sites More sharing options...
cgrbu Posted July 30, 2017 Report Share Posted July 30, 2017 before taking SL40 unit out of tray, tested before starting engine, transmission and reception clear as a bell. Did a quick removal checked pins for damage and re-installed. Did a start up and on initial transmissions had the static. Went flying and with higher power settings transmission okay, back to the barn and static not noticed on ground taxi... will see what happens on next flight....thanks to all who have had some suggestions Quote Link to comment Share on other sites More sharing options...
cgrbu Posted August 3, 2017 Report Share Posted August 3, 2017 to answer coppercity ...today the noise is as loud as before when hooked in to jacks behind pilot/pxx seats and with gen circuit breaker out, no change (engine running). I have had those jacks out and checked for corrosion (emery papered, but I may swap them out for new). I get perfect transmission and reception when I am hooked directly to forward panel jacks (see picture attached). I have added the extra gnd wires from Battery to #3 cylinder and back to the starter solenoid which has the ground wire connected to the interior gnd bus. Also I have installed new spark plugs NGK DCPR8E 4339 gapped at .028. Quote Link to comment Share on other sites More sharing options...
Tom Baker Posted August 3, 2017 Report Share Posted August 3, 2017 Those forward jacks are isolated from the intercom, and just go to the radio. If it is quite there your problem is not the radio, the noise is coming from or through the intercom. Something I have done before trouble shooting noise in the CT is to pull each breaker independently to see if one specific piece of equipment is causing the issue. I had one whos noise was created by the GPS. After installing a ground loop isolator the problem went away. Quote Link to comment Share on other sites More sharing options...
coppercity Posted August 3, 2017 Report Share Posted August 3, 2017 I have seen the aux music jack miswired cause noise, gps audio cable as well. Quote Link to comment Share on other sites More sharing options...
cgrbu Posted August 3, 2017 Report Share Posted August 3, 2017 thank you both for the comments... I will target the intercom. As well the mention of the GPS has me thinking of the recent problems I have had with it not coming online with the start-up. I had the centre console out a couple of times to ensure that the power cord is properly seated and I also shimmed the antennae feed at that time so it would not work loose. With your mention of the ground loop antennae, is that a part you can order from Garmin or an avionics shop? Quote Link to comment Share on other sites More sharing options...
Tom Baker Posted August 3, 2017 Report Share Posted August 3, 2017 It was a ground loop isolator for a 3.5mm plug. It was in the audio input not antenna. here is what I installed. PAC RCA Filter SNI-1/3.5 Here is a link from Amazon. https://www.amazon.com/PAC-SNI-1-3-5-3-5-mm-Isolator/dp/B001EAQTRI Quote Link to comment Share on other sites More sharing options...
cgrbu Posted August 3, 2017 Report Share Posted August 3, 2017 additionally I believe the autopilot servos may have been engaged while on the ground as my control stick has moved with a clicking sound. I pulled the circuit breaker for this as well to see if the noise would stop on the radio transmission, no change. Quote Link to comment Share on other sites More sharing options...
cgrbu Posted August 3, 2017 Report Share Posted August 3, 2017 thank you Tom for the part number Quote Link to comment Share on other sites More sharing options...
Anticept Posted August 4, 2017 Report Share Posted August 4, 2017 The PM3000 intercomms do not filter electrical noise very well. In addition, the choice of wiring used for audio leaves a lot to be desired. Hell, on other aircraft I have even seen untwisted wire used in some installs, it's embarrassing! Twisted wire does a substantial job to noise filtering when in close proximity to other wires that have fluctuating power. Outside of that, the switched mode power supplies used on many of the LEDs on flight design aircraft are garbage and have horrible RFI filtering, and that also likes to propagate back through the system. Quote Link to comment Share on other sites More sharing options...
cgrbu Posted August 4, 2017 Report Share Posted August 4, 2017 anticept, would the new LED landing light just installed have an effect even when not on? Quote Link to comment Share on other sites More sharing options...
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