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dean.psiropoulos(at)veriz
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 Posted: Sat Nov 10, 2007 11:56 pm Post subject: RV-List Digest: 3 Msgs - 11/07/07 |
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Functional checkout of my electrical system has gone well so far with no
smoked wiring or equipment. I bought an equivalent of an Odyssey 680 a
couple years ago and trickle charged it occasionally hoping it would at
least be good enough to do electrical checkout, first engine start and maybe
a few times around the pattern. But it appears that is not the case.
Voltmeter says there is 12.5 volts at the terminals but it can't produce
enough amps to fire the battery contactor or even make some sparks when
shorted, pretty pathetic. I substituted a Panasonic 4.5 amp hour sealed lead
acid battery that I bought second hand about 6 years ago. It's got enough
oomph for the checkout but I'll need a new 680 for 1st engine start.
I did a test on my magneto P-lead (one mag on left side, electronic on right
side)with an ohm meter. Thinking that when the key switch is in the off
position, the resistance across the p-lead should measure close to dead
short and, it does. By the same logic, I thought that when the mag was
ungrounded the resistance across the p-leads (I used a shielded wire with
the shield grounded at the magneto through the key switch, no local
grounding). But when I measured across the p-leads at the magneto the
resistance only went from 0.2 ohms to 0.4 ohms when I turned the key. Not
an appreciable increase in resistance but it was consistent (happens every
time) and measurable. I thought maybe I had a faulty key switch but not so,
I removed one p-lead from the mag and made the same measurement and the
resistance with the key in that mag's position read infinite. I suspect
that there is some thing about magnetos I don't know and that this is not a
problem but would like to be sure. Anybody ever done this test? Did you get
the same results?
Also checked out the VM-1000 and it seems to work fine except for dimming.
I used one of the B&C dimmers connected to the VM-1000 dimming input but I
don't seem to get any dimming action (backlight works ok). Anyone else
experience this? Have I missed something in the VM manual and it doesn't use
an external dimming input? Any thoughts? Thanks.
Dean
RV-6A N197DM
closer to 1st flight.
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acepilot(at)bloomer.net
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| Posted: Sun Nov 11, 2007 5:19 am Post subject: RV-List Digest: 3 Msgs - 11/07/07 |
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Remember that inside the mag, there is the set of points. One side of
the points is connected to ground and the other side is connected to the
P-Lead and one side of the coil. If the points are closed, you would
read very close to a short to ground (as you did). You might have to
rotate the engine (and I would suggest turning the prop backwards to
avoid an accidental start!). At some point, the points should open and
you would read an open with the ohm meter.
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)
DEAN PSIROPOULOS wrote:
| Quote: |
Functional checkout of my electrical system has gone well so far with no
smoked wiring or equipment. I bought an equivalent of an Odyssey 680 a
couple years ago and trickle charged it occasionally hoping it would at
least be good enough to do electrical checkout, first engine start and maybe
a few times around the pattern. But it appears that is not the case.
Voltmeter says there is 12.5 volts at the terminals but it can't produce
enough amps to fire the battery contactor or even make some sparks when
shorted, pretty pathetic. I substituted a Panasonic 4.5 amp hour sealed lead
acid battery that I bought second hand about 6 years ago. It's got enough
oomph for the checkout but I'll need a new 680 for 1st engine start.
I did a test on my magneto P-lead (one mag on left side, electronic on right
side)with an ohm meter. Thinking that when the key switch is in the off
position, the resistance across the p-lead should measure close to dead
short and, it does. By the same logic, I thought that when the mag was
ungrounded the resistance across the p-leads (I used a shielded wire with
the shield grounded at the magneto through the key switch, no local
grounding). But when I measured across the p-leads at the magneto the
resistance only went from 0.2 ohms to 0.4 ohms when I turned the key. Not
an appreciable increase in resistance but it was consistent (happens every
time) and measurable. I thought maybe I had a faulty key switch but not so,
I removed one p-lead from the mag and made the same measurement and the
resistance with the key in that mag's position read infinite. I suspect
that there is some thing about magnetos I don't know and that this is not a
problem but would like to be sure. Anybody ever done this test? Did you get
the same results?
Also checked out the VM-1000 and it seems to work fine except for dimming.
I used one of the B&C dimmers connected to the VM-1000 dimming input but I
don't seem to get any dimming action (backlight works ok). Anyone else
experience this? Have I missed something in the VM manual and it doesn't use
an external dimming input? Any thoughts? Thanks.
Dean
RV-6A N197DM
closer to 1st flight.
|
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acepilot(at)bloomer.net
Guest
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| Posted: Sun Nov 11, 2007 6:04 am Post subject: RV-List Digest: 3 Msgs - 11/07/07 |
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Oops, disregard my last post. Going through my Eisemann magneto service
book, it looks like no matter if the points are open or closed, you will
be reading through the primary of the coil to ground, so what you saw is
probably correct...ie a reading of 0.2 ohms or so greater than when the
switch was grounding the P lead through the ignition switch. I'll go
back under my rock now...;(
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)
Scott wrote:
| Quote: |
Remember that inside the mag, there is the set of points. One side of
the points is connected to ground and the other side is connected to
the P-Lead and one side of the coil. If the points are closed, you
would read very close to a short to ground (as you did). You might
have to rotate the engine (and I would suggest turning the prop
backwards to avoid an accidental start!). At some point, the points
should open and you would read an open with the ohm meter.
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)
DEAN PSIROPOULOS wrote:
>
> <dean.psiropoulos(at)verizon.net>
>
> Functional checkout of my electrical system has gone well so far with no
> smoked wiring or equipment. I bought an equivalent of an Odyssey 680 a
> couple years ago and trickle charged it occasionally hoping it would at
> least be good enough to do electrical checkout, first engine start
> and maybe
> a few times around the pattern. But it appears that is not the case.
> Voltmeter says there is 12.5 volts at the terminals but it can't produce
> enough amps to fire the battery contactor or even make some sparks when
> shorted, pretty pathetic. I substituted a Panasonic 4.5 amp hour
> sealed lead
> acid battery that I bought second hand about 6 years ago. It's got
> enough
> oomph for the checkout but I'll need a new 680 for 1st engine start.
>
> I did a test on my magneto P-lead (one mag on left side, electronic
> on right
> side)with an ohm meter. Thinking that when the key switch is in the off
> position, the resistance across the p-lead should measure close to dead
> short and, it does. By the same logic, I thought that when the mag was
> ungrounded the resistance across the p-leads (I used a shielded wire
> with
> the shield grounded at the magneto through the key switch, no local
> grounding). But when I measured across the p-leads at the magneto the
> resistance only went from 0.2 ohms to 0.4 ohms when I turned the
> key. Not
> an appreciable increase in resistance but it was consistent (happens
> every
> time) and measurable. I thought maybe I had a faulty key switch but
> not so,
> I removed one p-lead from the mag and made the same measurement and the
> resistance with the key in that mag's position read infinite. I suspect
> that there is some thing about magnetos I don't know and that this is
> not a
> problem but would like to be sure. Anybody ever done this test? Did
> you get
> the same results?
>
> Also checked out the VM-1000 and it seems to work fine except for
> dimming.
> I used one of the B&C dimmers connected to the VM-1000 dimming input
> but I
> don't seem to get any dimming action (backlight works ok). Anyone else
> experience this? Have I missed something in the VM manual and it
> doesn't use
> an external dimming input? Any thoughts? Thanks.
>
> Dean
> RV-6A N197DM
> closer to 1st flight.
>
>
|
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http://www.matronics.com/Navigator?RV-List |
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