Today's Message Index:
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1. 05:50 AM - Re: Butt Splice for #4 wire (johngoodman)
2. 04:16 PM - Re: Diagnostic Help Please: Audio is Weak and Scratchy (Jared Yates)
Message 1
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| Subject: | Re: Butt Splice for #4 wire |
toaster73(at)embarqmail.c wrote:
> John,
> Did I miss it - I am sorry, but can you explain how you discovered the
> problem? Was it complete disconnect? Was the break on the alternator end or
> firewall end?
> Thanks
> Chris Lucas
> N919AR
> 40072
>
> --
The break was on the starter power lug. I have two wires on that lug - a #2 from
the rear battery, and a #4 that goes around the engine to the lug on an ANL
type fuse connected to the alternator - that's how the battery recharges.
A couple of flights ago I noticed that I only had about 12V on the battery after
start, but my backup battery was fine. I figured the battery was beginning to
fail, or there was some kind of grounded lead. I was getting large amp draws
during start, so I figured that it had something to do with the starter/solenoid.
I pulled the cowling and concentrated on the positive lead on the solenoid,
but the big cables were getting in my way. I decided to remove them to get
more room.
The #4 looked fine as I removed the nut, but as soon as a pulled it off the lug,
the terminal was only hanging on by a couple of thin wires and a small piece
of the heatshrink. The only thing that had been keeping it together was the heatshrink
and the natural propensity of the wire to stay in place.
My only explanation is that the 7", or so, of cable between the terminal end and
the first adel clamp, had enough weight and motion to respond to vibrations,
and eventually fatigue the cable.
Hope this explains it.
John
--------
#40572 Phase One complete and flying.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=398235#398235
Message 2
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| Subject: | Re: Diagnostic Help Please: Audio is Weak and Scratchy |
Here's an update. I took the very nicely detailed instructions from
Charlie to the hangar today and tried running the various inputs
directly to the headset. The good news is that the 430 and iso amp
worked perfectly. When I got down to testing the intercom by itself,
I still had the problem, so I ran new temporary wires to my temporary
test jack, and everything worked. I started rebuilding from there,
with the pilot's mic jack first. When I added the phone jack, the
problem came back. I started checking continuity from the jack to the
intercom connector and found the problem- I had not grounded the
jacks. To verify the problem, I ran a jumper from the jack's ring to
the ground tab, and the problem went away immediately. Back when I
did the initial install, I had the phone jacks grounded locally to the
airframe. Some time later I read that it was better to isolate the
headset jacks from the airframe and ground them up front with the rest
of the avionics grounds, so I drilled the holes up to size and
installed the insulating washers. Then I omitted the step of running
the ground wires! Fortunately my jacks were wired with a 3-conductor
shielded cable, so I had an idle wire in the cable already. I spent a
few hours today getting those cables adjusted so that i could connect
the idle conductor. I had to leave before I could get it all wired up
to test, but I think this was one of my biggest problems. Thanks
again to Charlie for the strategy. Now that I have the equipment and
systems in place, I can test the rest of the wiring as I go, adding
one source at a time to make sure that I don't have any other
problems. This wasn't an option during the initial wiring, because I
didn't have the avionics on hand yet. One thing that I haven't done
yet is to run a separate ground wire for the 3.5mm audio in and audio
out jacks, which are mounted in the panel. Should I try to isolate
their grounds? I'm not sure if I'll be able to find an insulating
washer in that size anyway.
Chris's concern is a good one, which Flightcom addresses by installing
a little toggle switch at each jack station. In mono mode it opens
the circuit between the second audio output and the intercom. In
stereo mode it closes the circuit. If you configure it incorrectly,
the result is either a tone or a non-stereo output, depending on the
situation. That function appears to be working.
On Sat, Apr 6, 2013 at 3:14 PM, Christopher Cee Stone
<rv8iator@gmail.com> wrote:
> Jared...
>
> One other potential low impedance fault is if using stereo headphone jacks
> and connecting both tip and ring to audio high. When a mono headphone plug
> is used it shorts the ring to audio lo (ground) and results in low or no
> audio from the connected source(s).
>
> Chris Stone
> RV-8
>
>
> On Sat, Apr 6, 2013 at 4:52 AM, Jared Yates <email@jaredyates.com> wrote:
>>
>> <email@jaredyates.com>
>>
>> Thank you very much Charlie, I'll try those procedures and report back
>> when complete.
>>
>>
>>
>> On Apr 5, 2013, at 20:46, Charlie England <ceengland7@gmail.com> wrote:
>>
>> > <ceengland7@gmail.com>
>> >
>> > On 04/05/2013 03:40 PM, Jared Yates wrote:
>> >> <email@jaredyates.com>
>> >>
>> >> I've been testing my audio system and have encountered poor
>> >> performance. Does anyone have any suggestions for what to check?
>> >> Here is the problem:
>> >>
>> >> All audio through the headsets is too quiet, and pretty scratchy. This
>> >> applies to radio reception, intercom audio, Dynon voice out, and music
>> >> input. With the intercom volume, headset volume, and individual device
>> >> volume all the way up, the total volume is about where I would want to
>> >> have it with 25% volume selected instead. The issue seems to afflict
>> >> each of the various inputs to a similar degree.
>> >>
>> >> Here is the setup:
>> >> New construction, wired by me (a non-professional, so anything is
>> >> possible)
>> >> The airframe is a steel tube 4-place fuselage with the mic and audio
>> >> headset jacks isolated from ground, as verified by voltmeter
>> >> continuity checks.
>> >> I used shielded cables to connect the intercom and the mic and stereo
>> >> phone jacks, with the shields connected at intercom end to each other
>> >> and not connected to anything at the jacks.
>> >> I have a self-assembled AEC 9009 Audio Iso Amp handling VHF nav audio
>> >> on one channel, dynon warnings on one channel, left music in on one
>> >> channel, and right music in on one channel, with the 9009's output
>> >> going into the intercom aux input
>> >> The intercom is a Flightcom 403, with the pilot wires going to the
>> >> left front seat, copilot wires to the right front seat, and passenger
>> >> jacks to the back two seats.
>> >> The GNS430 is the only radio, with com audio routed directly to the
>> >> intercom per the intercom directions.
>> >> I'm testing with two known-good David Clark headsets (one stereo, one
>> >> mono) and one brand new Lightspeed headset, all with freshly buffed,
>> >> shiny connectors.
>> >> I'm using battery power only, since the engine is not installed
>> >> presently. I've tried the battery by itself and the battery with the
>> >> charger connected. The voltage range is about 13v to 14v for those
>> >> two cases, but I can't see that changing from one to the other makes
>> >> any difference in the audio system issues.
>> >>
>> >> Here is what I have tried so far with no improvements:
>> >> First, I unplugged aec9009. I lost the channels that run through it,
>> >> but the remaining intercom and VHF com audio were still the same.
>> >> Then I swapped intercom for the bypass plug that I built per the
>> >> intercom manual. this plug is designed to connect the pilot seat
>> >> jacks directly to the radio, so that the airplane can still function
>> >> as a single-place if the intercom is removed entirely. As with the
>> >> 9009, I lose intercom function in this configuration (as I should),
>> >> but the vhf com audio is still weak and scratchy.
>> >> I tried changing the Headsets around in various combinations to
>> >> various seats with no appreciable change.
>> >> I changed out the volume resistors in the AEC9009 to increase the
>> >> volume of those channels, and the volume did go up on the channel in
>> >> question, but the quality really suffered.
>> >> I'm not really sure what to try next. Does anyone have any
>> >> suggestions for what to check?
>> > The fuzzy part sounds like some segment in the audio chain is being
>> > overdriven by a source, or is being asked to supply more than it's capable
>> > of giving. The low level could be too much of a load on the output (load
>> > impedance too low). A partial short to ground (from an audio 'hi' to an
>> > audio 'Lo', or to the chassis) is the 1st thing that comes to mind. Having
>> > both fuzzy & low volume from multiple sources *might* mean that you have two
>> > or more outputs trying to feed into each other, with no isolation resistors
>> > between them. (This will make all affected outputs 'think' that they are
>> > effectively shorted to ground because each is trying to drive a very low
>> > impedance load.)
>> >
>> > So to proceed, 'Divide & conquer.'
>> >
>> > It's extremely unlikely that you have the same problem with every
>> > source, so job one is eliminating the known-good items. I'd get a set of
>> > clip leads, and extra phone jack, & start testing each source by itself,
>> > without it connected to any other component. Isolate the output line
>> > (typically 'audio hi' on the hookup diagram) from the rest of the plane.
>> > Hook a clip lead from that wire to the tip terminal of your spare jack. Hook
>> > another clip lead from the ground ('audio Lo') to the shield (ground)
>> > terminal of the jack. Plug in a known-good headset & listen to that source.
>> > Sound ok? If not troubleshoot settings, ground paths, etc. If good, move to
>> > the next source & repeat. Annddd repeat, until you've checked all or until
>> > you find a bad component.
>> >
>> > If all is good, hook one (and only one) source to the iso amp & move
>> > your test jack to the iso amp's output (with it hooked to nothing else). If
>> > bad, there's your problem. All good? that means the iso amp is almost
>> > certainly good, too.
>> >
>> > Hook the iso amp to the intercom's input again (with nothing else hooked
>> > to the input). Move the test jack to the intercom's output (with nothing
>> > else hooked up to the output lead). Listen again. If bad, check intercom
>> > settings (especially if there is an internal gain setting or aux input
>> > volume control in the intercom).
>> >
>> > All good? Without hooking up the 430, add one component to the iso amp &
>> > check for level/quality at the intercom output. (We've actually skipped a
>> > few steps by doing this, but if one iso input is good, odds are high that
>> > all will be good.)
>> >
>> > All sources (except 430) good? Use your test jack to check the 430, with
>> > its output connected to nothing but the test jack. Bad? There's your
>> > problem. Good? Proceed.
>> >
>> > Now look at how the 430 ties to the intercom. In your message, you say
>> > that the iso amp is hooked direct to the intercom. Is this a separate input
>> > on the intercom? It probably is, but if it's tied to the same input with the
>> > iso amp, that might well be your problem. Different input? Move your test
>> > jack to the intercom output & listen to the 430 through the intercom. Bad?
>> > Re-check wiring & intercom settings, then check the intercom itself, if
>> > possible. Still good? Re-check your headphone wiring harness in the plane.
>> >
>> > Having said all that, I'll say this: I've worked on a couple of 430
>> > installations for friends, & they can be real snakes to troubleshoot. The
>> > most common issue is ground pins on the d-Sub connectors. There are quite
a
>> > few, & if you miss one, stuff isn't going to work (not every ground terminal
>> > is common to every other ground terminal in those d-Sub connectors). On one
>> > system, I spoke with directly to a Garmin factory tech while holding the
>> > installation manual in my hand, and read off the pins that were connected.
>> > Even the Garmin tech failed to mention a (ground) pin that needed to be
>> > connected.
>> >
>> > Charlie
>> > (pro audio tech, consumer electronics tech and industrial electronics
>> > tech in various former lives)
>> >
>> >
>> >
>> >
>>
>>
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