---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 11/03/20: 16 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:35 AM - isolation resistors (rd2) 2. 05:56 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Ernest Christley) 3. 07:00 AM - Re: isolation resistors (Charlie England) 4. 07:22 AM - Re: Engine compartment fuse? (johnbright) 5. 08:43 AM - Re: isolation resistors (rd2) 6. 09:28 AM - Magnetos (Efraim Otero) 7. 10:06 AM - Re: Magnetos (user9253) 8. 10:41 AM - Re: ADS-B and Transponder antenna... (andymeyer) 9. 10:43 AM - Re: Magnetos (Sebastien) 10. 10:44 AM - Re: isolation resistors (dj_theis) 11. 11:32 AM - Re: Magnetos (Charlie England) 12. 12:57 PM - Re: Magnetos (Kelly McMullen) 13. 01:49 PM - Re: Re: isolation resistors (rd2) 14. 02:05 PM - Automotive spark plugs () 15. 02:20 PM - Re: Magnetos (Stuart Hutchison) 16. 07:21 PM - Magneto Switch (Paul Millner) ________________________________ Message 1 _____________________________________ Time: 05:35:01 AM PST US From: rd2 Subject: AeroElectric-List: isolation resistors Hi group, I need to merge 3 audio signals (all low power) and feed them to pin T (non-switched audio input) of a King KMA 24 audio panel. The purpose is to sufficiently isolate the signals without significant attenuation. The KMA 24 input impedance is listed as 500 ohm. The impedance of the sources is not known except that they are intended to be amplified. The sources are: Warnings from Monroy Traffic Scope, Traffic Warnings from GNX 375, and AoA warnings from uAvionix AV-20-S. Should I use resistors in series with each source and what value would you recommend? 4.7 kohm ? Thanks Rumen ________________________________ Message 2 _____________________________________ Time: 05:56:58 AM PST US From: Ernest Christley Subject: Re: AeroElectric-List: DIY LED landing light -- Wing skin as heat sink? Good gawd!=C2- Those lights are ridiculous bright. Here's a question:=C2- If I strap enough of these to my wings, will it ef fectively nullify the day only restriction on my operating limitations?=C2 - :-) On Monday, November 2, 2020, 9:19:22 PM EST, Finn Lassen wrote: On 11/2/2020 6:05 PM, Ernest Christley wrote: As for reflectors, are they really needed?=C2- The LED has a light patt ern that puts nearly all of the light forward to begin with.=C2- And LEDs with a 45 degree pattern are available.=C2- The ones I used from MPJA ha d a 160 degree spread, but a chart of the intensity showed very little at t he ends of that range. Well, my goal is to light up at least 1,000 feet of the runway, preferably 3,000. Charlie referred to a landing light with a 3 degree beam width. I guess with a strong enough LED (like 100W or 9,000 lumens) the bean widt h may not be all that important. For the reflector for the https://www.stratusleds.com/module is "the beam is around 15 degrees with a soft falloff". But definitely a good point. Finn | | Virus-free. www.avast.com | ________________________________ Message 3 _____________________________________ Time: 07:00:45 AM PST US From: Charlie England Subject: Re: AeroElectric-List: isolation resistors On Tue, Nov 3, 2020 at 7:40 AM rd2 wrote: > > Hi group, > > I need to merge 3 audio signals (all low power) and feed them to pin T > (non-switched audio input) of a King KMA 24 audio panel. The purpose is to > sufficiently isolate the signals without significant attenuation. > The KMA 24 input impedance is listed as 500 ohm. The impedance of the > sources is not known except that they are intended to be amplified. The > sources are: Warnings from Monroy Traffic Scope, Traffic Warnings from GNX > 375, and AoA warnings from uAvionix AV-20-S. > Should I use resistors in series with each source and what value would you > recommend? 4.7 kohm ? > Thanks > Rumen > Since all are aviation devices, they *should* be capable of driving a 600 ohm load at adequate volume. So the goal is to keep the load they see above 600 ohms. Each source impedance will likely be either a resistor in series with its output, or the very low impedance of the output stage itself. If you assume that source impedance is zero for each device (it'll more likely be 50-100 ohms), then the load each device will see will be the series-parallel total resistance of its own series resistor (which you're adding) and the audio panel input (600 ohms), and the series resistors of the other two sources. The signal level will be attenuated by around 50%, which will usually be OK. Being lazy & avoiding the math, if you start with around 1K ohms for each series resistor, it'll likely work fine. You might be able to go as low as 300-400 ohms. You're balancing signal loss to series resistance, vs signal loss due to overloading the output with too low a combined load resistance. (Little risk of damage; just a signal that's too weak.) The above may or may not work if you add consumer electronics to the mix. There are zero 'standards' to how consumer gear does things, and the output levels are almost always too low to work without 'help'. Charlie ________________________________ Message 4 _____________________________________ Time: 07:22:40 AM PST US Subject: AeroElectric-List: Re: Engine compartment fuse? From: "johnbright" This may be more than what the OP was asking but I made notes for myself and I'll share them here. Speaking of bolt-down fuses and current limiters, from what I have seen there are three bolt center-to-center distances: 61 mm, 2", and 30 mm. B&C shows only 61 mm on their website: Bussman ANL current limiters and their holders. 61 mm centers: Bussman ANN 10 to 800 A fast-acting current limiters. Bussman ANL 35 to 750 A current limiters. I gather ANL is originally a Bussman term that has been co-opted by others. Renology ANL 61 mm fuses. Renology calls it a fuse and it looks about as fast as an ANN fast-acting current limiter. 2" centers: Bussman AMG 100 to 300 A fuses. Littlefuse MEGA 40 to 100 A fuses. 30 mm centers: Bussmann AMI 30 to 150 A fuses. Seems to be practically the same as MIDI. Littelfuse MIDI 23 to 200 A fuses. Littlefuse BF1 23 to 200 A fuses. Seems to be practically the same as MIDI. Various offerings of fuses under the generic name MANL, mini ANL. When fusess are listed as MEG they mean MEGA. -------- John Bright, RV-6A, at FWF, O-360 Z-101 single batt dual alt SDS EM-5-F. john_s_bright@yahoo.com, Newport News, Va https://drive.google.com/drive/folders/1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K Read this topic online here: http://forums.matronics.com/viewtopic.php?p=499220#499220 ________________________________ Message 5 _____________________________________ Time: 08:43:09 AM PST US From: rd2 Subject: Re: AeroElectric-List: isolation resistors Thanks Charlie. R ----- Original Message ----- From: Charlie England Sent: Tue, 03 Nov 2020 09:52:24 -0500 (EST) Subject: Re: AeroElectric-List: isolation resistors On Tue, Nov 3, 2020 at 7:40 AM rd2 wrote: Hi group, I need to merge 3 audio signals (all low power) and feed them to pin T (non-switched audio input) of a King KMA 24 audio panel. The purpose is to sufficiently isolate the signals without significant attenuation. The KMA 24 input impedance is listed as 500 ohm. The impedance of the sources is not known except that they are intended to be amplified. The sources are: Warnings from Monroy Traffic Scope, Traffic Warnings from GNX 375, and AoA warnings from uAvionix AV-20-S. Should I use resistors in series with each source and what value would you recommend? 4.7 kohm ? Thanks Rumen Since all are aviation devices, they *should* be capable of driving a 600 ohm load at adequate volume. So the goal is to keep the load they see above 600 ohms. Each source impedance will likely be either a resistor in series with its output, or the very low impedance of the output stage itself. If you assume that source impedance is zero for each device (it'll more likely be 50-100 ohms), then the load each device will see will be the series-parallel total resistance of its own series resistor (which you're adding) and the audio panel input (600 ohms), and the series resistors of the other two sources. The signal level will be attenuated by around 50%, which will usually be OK. Being lazy & avoiding the math, if you start with around 1K ohms for each series resistor, it'll likely work fine. You might be able to go as low as 300-400 ohms. You're balancing signal loss to series resistance, vs signal loss due to overloading the output with too low a combined load resistance. (Little risk of damage; just a signal that's too weak.) The above may or may not work if you add consumer electronics to the mix. There are zero 'standards' to how consumer gear does things, and the output levels are almost always too low to work without 'help'. Charlie ________________________________ Message 6 _____________________________________ Time: 09:28:24 AM PST US From: Efraim Otero Subject: AeroElectric-List: Magnetos Dear All: I wanted to see if I could get inputs to understand an issue I am having with my Bendix magnetos. My biplane, an O 200 powered Fisher Celebrity has what I call a partial Electric system. One 12 V 18 Ah battery that connects directly to a skytec starter. This starter has a switch that in turn leads to a starter pushbutton. It also has a key switch for the magnetos: Off, Left, right, both. I tried to start the engine and it motors while pushing the starter pushbutton, with the starter switch on and magnetos on both. However the engine does not catch. Also, if I turn the mags off, the engine also motors but obviously does not ignite. What might be going on? -Battery issues? not enough charge/power? -Mag issues? not getting any spark (Should the engine be turning at some specific revs on cranking for it to generate a spark? -Ignition harness? -Spark plugs? Any suggestions as to how to troubleshoot? I am getting fuel to the engine as I can smell it. It has no fuel pump, justgravit feed. Starter motors slowly, although it does not "seem un normal" (purely perception of mine!) Please advise, Efraim ________________________________ Message 7 _____________________________________ Time: 10:06:09 AM PST US Subject: AeroElectric-List: Re: Magnetos From: "user9253" Possible magneto impulse coupling failure? -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=499231#499231 ________________________________ Message 8 _____________________________________ Time: 10:41:47 AM PST US Subject: AeroElectric-List: Re: ADS-B and Transponder antenna... From: "andymeyer" Bob, If you'd like a set of antenna to test and try out with the VNA, I can get a couple on their way to you - where do I send them? Andy nuckolls.bob(at)aeroelect wrote: > At 06:46 PM 11/1/2020, you wrote: > > > > > Here's another useful resource for learning the nanoVNA. It's a demo board that you connect to the device in order to learn what the test response should look like for various kinds of circuits. > > > > https://preview.tinyurl.com/yxz2hast (https://preview.tinyurl.com/yxz2hast) > > I'd seen that offered on Banggood . . . probably > ought to have one. > > I do have an earlier version of the NanoVNA that > was barely used used before I acquired the VNATiny > that comes with some sophisticated PC based > management apps . . . but it's NOT self contained. > There are some apps that run in hand held Android > devices . . . I need to explore that further. > > I ordered a 4", 1.5G version of the NanoVNA last > night . . . much handier for field and/or quick > look-see tasks. I just may have a very slightly > used NanoVNA for sale pretty soon! > > > > Bob . . . Read this topic online here: http://forums.matronics.com/viewtopic.php?p=499234#499234 ________________________________ Message 9 _____________________________________ Time: 10:43:27 AM PST US From: Sebastien Subject: Re: AeroElectric-List: Magnetos My advice would be to have a mechanic troubleshoot. In the meantime, is this a new installation that has never run or is this a new problem? On Tue, Nov 3, 2020 at 9:37 AM Efraim Otero wrote: > Dear All: > I wanted to see if I could get inputs to understand an issue I am having > with my Bendix magnetos. > My biplane, an O 200 powered Fisher Celebrity has what I call a partial > Electric system. One 12 V 18 Ah battery that connects directly to a skytec > starter. This starter has a switch that in turn leads to a starter > pushbutton. > It also has a key switch for the magnetos: Off, Left, right, both. > I tried to start the engine and it motors while pushing the starter > pushbutton, with the starter switch on and magnetos on both. However the > engine does not catch. > Also, if I turn the mags off, the engine also motors but obviously does > not ignite. > What might be going on? > -Battery issues? not enough charge/power? > -Mag issues? not getting any spark (Should the engine be turning at some > specific revs on cranking for it to generate a spark? > -Ignition harness? > -Spark plugs? > Any suggestions as to how to troubleshoot? > I am getting fuel to the engine as I can smell it. It has no fuel pump, > justgravit feed. Starter motors slowly, although it does not "seem un > normal" (purely perception of mine!) > > Please advise, > Efraim > ________________________________ Message 10 ____________________________________ Time: 10:44:02 AM PST US Subject: AeroElectric-List: Re: isolation resistors From: "dj_theis" rd2(at)dejazzd.com wrote: > Hi group, > > I need to merge 3 audio signals (all low power) and feed them to pin T (non-switched audio input) of a King KMA 24 audio panel. The purpose is to sufficiently isolate the signals without significant attenuation. > The KMA 24 input impedance is listed as 500 ohm. The impedance of the sources is not known except that they are intended to be amplified. The sources are: Warnings from Monroy Traffic Scope, Traffic Warnings from GNX 375, and AoA warnings from uAvionix AV-20-S. > Should I use resistors in series with each source and what value would you recommend? 4.7 kohm ? > Thanks > Rumen This may be overkill but I had a similar need and used the DIY board from Proffessor Nuckolls. http://www.aeroelectric.com/DIY/Audio_Iso_Amp_9009-700L.pdf Wired it up and tested it on the bench with the wiring shown in the attached and shown in the lower right corner. All tested well with good volume control and excellent isolation. Have not yet run the engine on the plane but don't expect any problems. the PM3000 has an auto music silence fetaure when recieving or PTT is depressed. All worked well. Very pleased with the outcome. Dan Theis -------- Scratch building Sonex #1362 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=499235#499235 Attachments: http://forums.matronics.com//files/z16m_revmaster_2300_r9_sht_2_115.pdf ________________________________ Message 11 ____________________________________ Time: 11:32:35 AM PST US From: Charlie England Subject: Re: AeroElectric-List: Magnetos On Tue, Nov 3, 2020 at 11:37 AM Efraim Otero wrote: > Dear All: > I wanted to see if I could get inputs to understand an issue I am having > with my Bendix magnetos. > My biplane, an O 200 powered Fisher Celebrity has what I call a partial > Electric system. One 12 V 18 Ah battery that connects directly to a skytec > starter. This starter has a switch that in turn leads to a starter > pushbutton. > It also has a key switch for the magnetos: Off, Left, right, both. > I tried to start the engine and it motors while pushing the starter > pushbutton, with the starter switch on and magnetos on both. However the > engine does not catch. > Also, if I turn the mags off, the engine also motors but obviously does > not ignite. > What might be going on? > -Battery issues? not enough charge/power? > -Mag issues? not getting any spark (Should the engine be turning at some > specific revs on cranking for it to generate a spark? > -Ignition harness? > -Spark plugs? > Any suggestions as to how to troubleshoot? > I am getting fuel to the engine as I can smell it. It has no fuel pump, > justgravit feed. Starter motors slowly, although it does not "seem un > normal" (purely perception of mine!) > > Please advise, > Efraim > If the impulse coupler is working, and you have a combustible mixture in the cylinder, the engine should fire as the piston passes top dead center, even if the prop is barely moving. You can troubleshoot the impulse-coupled mag by: 1. remove ALL the spark plug wires, and at least one plug from each cylinder (safety) 2. screw the plugs onto the plug wires for the impulse mag, and make sure the shell of the plugs is touching the engine. 3. switch on the impulse mag. if you're not absolutely sure which side is the impulse mag, turn the mag switch to 'both' to ensure that the impulse coupled mag is hot. 4. rotate the prop, and watch the plugs each time the impulse coupler fires (makes a sharp 'clack' sound). One plug should spark each time the impulse coupler fires. Continue to rotate the prop, watching the plugs, until you've heard at least 8 'clacks' (enough to fire each plug twice). If you get no spark on any of the plugs attached to the impulse mag, either the mag is grounded, or something inside the mag is defective. It's remotely possible that all 4 plug wires are bad, or all 4 plugs are bad, but that's not where I'd start. All the above assumes that this is a 'new' problem; that the engine has recently been running OK. If you're running mogas (at least here in the USA), know that if fuel has been sitting in the fuel bowl of the carb for more than a couple of weeks, the engine will be very hard to start until all the stale fuel is pumped out of the bowl, and fresh gas fills the bowl. (Ask me how I know this....) Charlie ________________________________ Message 12 ____________________________________ Time: 12:57:08 PM PST US Subject: Re: AeroElectric-List: Magnetos From: Kelly McMullen All good advice. The left mag is normally the impulse mag. So for the test only activate the left mag. If nothing try again with only right mag on. Note, engine will crank faster with a plug out of each cylinder. Voltage only matters to starter, not to mags, as they don't get any battery power. If you hear noticeable slowing in the cranking, time to recharge the battery. On 11/3/2020 12:21 PM, Charlie England wrote: > > > On Tue, Nov 3, 2020 at 11:37 AM Efraim Otero > wrote: > > Dear All: > I wanted to see if I could get inputs to understand an issue I am > having with my Bendix magnetos. > My biplane, an O 200 powered Fisher Celebrity has what I call a > partial Electric system. One 12 V 18 Ah battery that connects > directlyto a skytec starter. This starter has a switch that in turn > leads to a starter pushbutton. > It also has a key switch for the magnetos: Off, Left, right, both. > I tried to start the engine and it motors while pushing the starter > pushbutton, with the starter switch on and magnetos on both. However > the engine does not catch. > Also, if I turn the mags off, the engine also motors but obviously > does not ignite. > What might be going on? > -Battery issues? not enough charge/power? > -Mag issues? not getting any spark (Should the engine be turning at > some specific revs on cranking for it to generate a spark? > -Ignition harness? > -Spark plugs? > Any suggestions as to how to troubleshoot? > I am getting fuel to the engine as I can smell it. It has no fuel > pump, justgravit feed. Starter motors slowly, although it does not > "seem un normal" (purely perception of mine!) > > Please advise, > Efraim > > > If the impulse coupler is working, and you have a combustible mixture in > the cylinder, the engine should fire as the piston passes top dead > center, even if the prop is barely moving. You can troubleshoot the > impulse-coupled mag by: > > 1. remove ALL the spark plug wires, and at least one plug from each > cylinder (safety) > 2. screw the plugs onto the plug wires for the impulse mag, and make > sure the shell of the plugs is touching the engine. > 3. switch on the impulse mag. if you're not absolutely sure which side > is the impulse mag, turn the mag switch to 'both' to ensure that the > impulse coupled mag is hot. > 4. rotate the prop, and watch the plugs each time the impulse coupler > fires (makes a sharp 'clack' sound). > > One plug should spark each time the impulse coupler fires. Continue to > rotate the prop, watching the plugs, until you've heard at least 8 > 'clacks' (enough to fire each plug twice). > > If you get no spark on any of the plugs attached to the impulse mag, > either the mag is grounded, or something inside the mag is defective. > It's remotely possible that all 4 plug wires are bad, or all 4 plugs are > bad, but that's not where I'd start. > > All the above assumes that this is a 'new' problem; that the engine has > recently been running OK. If you're running mogas (at least here in the > USA), know that if fuel has been sitting in the fuel bowl of the carb > for more than a couple of weeks, the engine will be very hard to start > until all the stale fuel is pumped out of the bowl, and fresh gas fills > the bowl. (Ask me how I know this....) > > Charlie > > > ________________________________ Message 13 ____________________________________ Time: 01:49:52 PM PST US From: rd2 Subject: Re: AeroElectric-List: Re: isolation resistors I am sure this would work, but I already have an audio panel - which in itself is an iso amp and already using all the inputs (except for the ADF, which recently failed; yes there is such a thing like ADF :) - so adding another iso amp would really be overkill in this case.... besides it's a certified bird... and I was looking for a lazy non-complex solution. Thanks anyway. R ----- Original Message ----- From: dj_theis Sent: Tue, 03 Nov 2020 13:36:21 -0500 (EST) Subject: AeroElectric-List: Re: isolation resistors rd2(at)dejazzd.com wrote: > Hi group, > > I need to merge 3 audio signals (all low power) and feed them to pin T (non-switched audio input) of a King KMA 24 audio panel. The purpose is to sufficiently isolate the signals without significant attenuation. > The KMA 24 input impedance is listed as 500 ohm. The impedance of the sources is not known except that they are intended to be amplified. The sources are: Warnings from Monroy Traffic Scope, Traffic Warnings from GNX 375, and AoA warnings from uAvionix AV-20-S. > Should I use resistors in series with each source and what value would you recommend? 4.7 kohm ? > Thanks > Rumen This may be overkill but I had a similar need and used the DIY board from Proffessor Nuckolls. http://www.aeroelectric.com/DIY/Audio_Iso_Amp_9009-700L.pdf Wired it up and tested it on the bench with the wiring shown in the attached and shown in the lower right corner. All tested well with good volume control and excellent isolation. Have not yet run the engine on the plane but don't expect any problems. the PM3000 has an auto music silence fetaure when recieving or PTT is depressed. All worked well. Very pleased with the outcome. Dan Theis -------- Scratch building Sonex #1362 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=499235#499235 Attachments: http://forums.matronics.com//files/z16m_revmaster_2300_r9_sht_2_115.pdf ________________________________ Message 14 ____________________________________ Time: 02:05:40 PM PST US From: Subject: AeroElectric-List: Automotive spark plugs Hi, is there any experience using a slick magneto with automotive spark plugs and automotive ignition wire. Appreciate reading what you saw with that configuration. I am flying a Lancair 360 with a Lyco 360, one electric iginition and a standard Slick magneto. Thanks for your reply, Peter D-EPSO ________________________________ Message 15 ____________________________________ Time: 02:20:44 PM PST US From: Stuart Hutchison Subject: Re: AeroElectric-List: Magnetos For safetys sake, I think its worth clarifying some potential aspects of your setup Efraim. Normally a rotary Off, Left, Right, Both switch also has a Start position, which momentarily grounds the Right magneto as long as the switch is in the Start position. I you have a separate start button (which is not likely to ground the Right magneto), then be very certain whether or not your Right magneto also has an impulse coupling to retard the spark(s). If it does, then by all means start on Both. If not, you only ever want to be starting the engine on Left magneto. This ensures the Right magneto is grounded and cannot fire the plugs well before Top Dead Centre (TDC), which can cause engine kick-back and damage the gearbox and accessories or worse, you if you happen to be hand-swinging the engine. Some Bendix magnetos have a tab inside the capacitor cover that grounds the magneto when the P-lead is removed, but if you disconnect the magnetos P-leads for any reason there is real potential for the magnetos to be LIVE and dangerous. Dont forget that magnetos generate their own spark independent of whether the electrical system is on or off, so the only way to stop them working is by grounding the magneto circuit via the 'P-lead and switch, which must be maintained in good condition for obvious reasons. V/r Stuart > On 4 Nov 2020, at 7:48 am, Kelly McMullen wrote: > > > All good advice. The left mag is normally the impulse mag. So for the test only activate the left mag. If nothing try again with only right mag on. Note, engine will crank faster with a plug out of each cylinder. > Voltage only matters to starter, not to mags, as they don't get any battery power. If you hear noticeable slowing in the cranking, time to recharge the battery. > > On 11/3/2020 12:21 PM, Charlie England wrote: >> On Tue, Nov 3, 2020 at 11:37 AM Efraim Otero > wrote: >> Dear All: >> I wanted to see if I could get inputs to understand an issue I am >> having with my Bendix magnetos. >> My biplane, an O 200 powered Fisher Celebrity has what I call a >> partial Electric system. One 12 V 18 Ah battery that connects >> directly to a skytec starter. This starter has a switch that in turn >> leads to a starter pushbutton. >> It also has a key switch for the magnetos: Off, Left, right, both. >> I tried to start the engine and it motors while pushing the starter >> pushbutton, with the starter switch on and magnetos on both. However >> the engine does not catch. >> Also, if I turn the mags off, the engine also motors but obviously >> does not ignite. >> What might be going on? >> -Battery issues? not enough charge/power? >> -Mag issues? not getting any spark (Should the engine be turning at >> some specific revs on cranking for it to generate a spark? >> -Ignition harness? >> -Spark plugs? >> Any suggestions as to how to troubleshoot? >> I am getting fuel to the engine as I can smell it. It has no fuel >> pump, justgravit feed. Starter motors slowly, although it does not >> "seem un normal" (purely perception of mine!) >> Please advise, >> Efraim If the impulse coupler is working, and you have a combustible mixture in the cylinder, the engine should fire as the piston passes top dead center, even if the prop is barely moving. You can troubleshoot the impulse-coupled mag by: >> 1. remove ALL the spark plug wires, and at least one plug from each cylinder (safety) >> 2. screw the plugs onto the plug wires for the impulse mag, and make sure the shell of the plugs is touching the engine. >> 3. switch on the impulse mag. if you're not absolutely sure which side is the impulse mag, turn the mag switch to 'both' to ensure that the impulse coupled mag is hot. >> 4. rotate the prop, and watch the plugs each time the impulse coupler fires (makes a sharp 'clack' sound). >> One plug should spark each time the impulse coupler fires. Continue to rotate the prop, watching the plugs, until you've heard at least 8 'clacks' (enough to fire each plug twice). >> If you get no spark on any of the plugs attached to the impulse mag, either the mag is grounded, or something inside the mag is defective. It's remotely possible that all 4 plug wires are bad, or all 4 plugs are bad, but that's not where I'd start. >> All the above assumes that this is a 'new' problem; that the engine has recently been running OK. If you're running mogas (at least here in the USA), know that if fuel has been sitting in the fuel bowl of the carb for more than a couple of weeks, the engine will be very hard to start until all the stale fuel is pumped out of the bowl, and fresh gas fills the bowl. (Ask me how I know this....) >> Charlie > > > ________________________________ Message 16 ____________________________________ Time: 07:21:58 PM PST US Subject: AeroElectric-List: Magneto Switch From: Paul Millner > Normally a rotary Off, Left, Right, Both switch also has a Start position, which momentarily grounds the Right magneto as long as the switch is in the Start position The shorting function is selectable by jumper... on start, you can ground the right, the left, none, or if you're perverse, both... by changing jumpers. 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