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do I need to change my capacitor

 
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AirEupora



Joined: 01 Nov 2009
Posts: 186
Location: Dixon, CA

PostPosted: Tue Jun 21, 2016 6:22 am    Post subject: do I need to change my capacitor Reply with quote

When I built my plane I got a copy of Bob N Electrical manual and started following his advice on the way I should build my system. One of the first things I did was install the capacitor on the Jabiru electrical charging system. That was four years ago and hundred hours. I have had a couple of things happen to charging system. Burnt Molex plug, replace with block and terminals. This last incident was the voltage regulator went out, but it took couple of systems with it. I was flying with the Trio/MGL auto-pilot on and the circuit breaker popped. I waited a minute then pushed it back in and it popped again. I left it out for the rest of the flight. I observed that my voltage had dropped to 12.8, but it did not enter into my mind that I had loss voltage. Over the next couple of flights I started having starting problems after a flight. I finally figured out that my voltage regulator was bad. I replace it. Then started finding burnt resistors on the auto-pilot wiring, a burnt diode on the battery charging wire. It was still working correctly. Then Matt, at MGL found my mother board damaged.

Today I read on the Europa List that I should check or replace my capacitor. Apparently there is only one check I can do. I'm wondering if I should just replace it for peace of mind as I'm planning on heading to KOSH in July.

Rick Stockton
N120EJ
3300L


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PostPosted: Tue Jun 21, 2016 7:55 am    Post subject: do I need to change my capacitor Reply with quote

Subject: do I need to change my capacitor
From: "AirEupora" <AirEupora(at)sbcglobal.net>
To: aeroelectric-list(at)matronics.com


--> AeroElectric-List message posted by: "AirEupora" <AirEupora(at)sbcglobal.net>


When I built my plane I got a copy of Bob N Electrical manual and started following his advice on the way I should build my system. One of the first things I did was install the capacitor on the Jabiru electrical charging system. That was four years ago and hundred hours. I have had a couple of things happen to charging system.

Burnt Molex plug, replace with block and terminals.

These connectors would not have been my
first choice for power wiring . . . I remember
seeing the open-barrel, b-crimp pins from
AMP, Inc back about 1968 when they were being
incorporated into Cessna's production harnesses.
They looked pretty cheesy to me . . . but
they have stood the test of time.

Having said that, they ARE very process and
environment sensitive. They must be properly
crimped and they have to be kept dry. It would
have been interesting to inspect the carcass
to see if we could deduce root cause. In any
case, the 'upgrade' to terminal block was
a safe bet.

This last incident was the voltage regulator went out, but it took couple of systems with it. I was flying with the Trio/MGL auto-pilot on and the circuit breaker popped. I waited a minute then pushed it back in and it popped again. I left it out for the rest of the flight. I observed that my voltage had dropped to 12.8, but it did not enter into my mind that I had loss voltage.

If you had a low volts warning system, it would
have been flashing for anything below 13.5 volts.
The battery cannot be charged with voltages that
low. 14.2 to 14.6 is the target.

Over the next couple of flights I started having starting problems after a flight. I finally figured out that my voltage regulator was bad. I replace it. Then started finding burnt resistors on the auto-pilot wiring, a burnt diode on the battery charging wire. It was still working correctly. Then Matt, at MGL found my mother board damaged.

Where is this diode in the system? Did you pattern
your system to a Z-figure?

Today I read on the Europa List that I should check or replace my capacitor. Apparently there is only one check I can do. I'm wondering if I should just replace it for peace of mind as I'm planning on heading to KOSH in July.

The capacitor is not a critical operational
device. Unless you've suffered an extended
over-voltage condition, the capacitor is
probably fine. Do you have ov protection?

What are your bus voltage readings with the
new regulator? Can you share a copy of your
architecture drawings with us?

Did your autopilot repair guy offer a probable
cause for what was discovered in the damage
patterns?

It's not clear to me that 'smoked' components
are necessarily linked to regulator failure
unless there was a sustained over-voltage
condition prior to the failure that caused it
to go belly-up. The constellation of failures
you've cited may well be separate incidents
with their own root causes.




Bob . . .


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AirEupora



Joined: 01 Nov 2009
Posts: 186
Location: Dixon, CA

PostPosted: Sat Jun 25, 2016 6:26 am    Post subject: Re: do I need to change my capacitor Reply with quote

The MGL provides for the low voltage readings, but I did not catch it. I was flying around with the battery voltage being shown.
With the new voltage regulator I'm showing 13.8v to 14.4v volts during flight. If I turn on landing lights it will drop to about 13.4v.
Yes, I pattern the diode to the Jabiru figure, but did not install the over protection. I'm now planning on doing that when I return from KOSH.
Trio Avionics only told me that the mother boards were burnt. The same for MGL.
I'll see if I can find a architecture drawings. Most of mine are hand drawn as I could never find a computer drawing program that I could use effectively.
Thanks for the help.


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user9253



Joined: 28 Mar 2008
Posts: 1922
Location: Riley TWP Michigan

PostPosted: Sat Jun 25, 2016 11:41 am    Post subject: Re: do I need to change my capacitor Reply with quote

Quote:
Most of mine are hand drawn as I could never find a computer drawing program that I could use effectively.

Try a free program called ExpressSCH.
https://www.expresspcb.com/expresssch
It is very easy to learn and use. The program is intended for designing printed circuit boards. The company makes their money by selling PCBs. The program has two parts, the schematic part and the PCB layout part. Just the schematic part needs to be used to make a schematic of your aircraft electrical system. Designs can be printed. I use a another free program called CutePDF Writer to emulate a printer. It will save an ExpressSCH design as a PDF file that can be shared and zoomed in on without blurring.
http://www.cutepdf.com/Products/CutePDF/writer.asp


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PostPosted: Sun Jun 26, 2016 10:40 am    Post subject: do I need to change my capacitor Reply with quote

At 09:26 AM 6/25/2016, you wrote:
Quote:
--> AeroElectric-List message posted by: "AirEupora" <AirEupora(at)sbcglobal.net>

The MGL provides for the low voltage readings, but I did not catch it. I was flying around with the battery voltage being shown.
With the new voltage regulator I'm showing 13.8v to 14.4v volts during flight. If I turn on landing lights it will drop to about 13.4v.
Yes, I pattern the diode to the Jabiru figure, but did not install the over protection. I'm now planning on doing that when I return from KOSH.
Trio Avionics only told me that the mother boards were burnt. The same for MGL.
I'll see if I can find a architecture drawings. Most of mine are hand drawn as I could never find a computer drawing program that I could use effectively.

Unless you're already proficient in CAD
drawing systems, the FAST and very effective
way to document your airplane goes something
like this.

Build a page-per-system wire book in a 3-ring
binder using #2 pencil and 'pink pearl' eraser.
Neat doesn't count at this stage. Just get all
the data down on paper so you don't have to
'go back an look' to refresh your memory of things
you did perhaps years ago.

Every time you make a change, record it. But keep
EACH page simple. Bus, breaker/fuse, wire, switch,
wire, connector, gizmo, wire, ground. This litany
might describe a landing light. Obviously, some
will be more complex but in terms of the WHOLE
airplane, each page is simple.

Download this document and check out the wirebook
pages in the back . . .

http://tinyurl.com/zlco6ke

These are examples of page-per-system drawings
that illustrate the technique for illustrating
wire segments, how and where they are terminated
and how to list all of the components and materials
that go into crafting that one system.

Make the same kinds of drawings for your airplane
filling in details as you go along. The 3-ring
binder on the shop-bench is all the tooling you
need.

When the airplane is all done and depending on
how legible your first-pass work is, you may
choose to redraw the work . . . use a straight
edge and gel pen. You can even draw your final
document on top of your draft document using
the draft data as a guide. When the final document
is complete and totally dry, use the pink pearl to
remove the pencil lines and smudges.

It takes less practice to go this route than to
search out, install and learn to use any kind
of CAD program. If you're going to do this stuff
for a living, having a CAD program may be useful.
If this but one of a very few numbers of airplanes
you're going to build, paper, pencil, eraser and
pen are excellent, time proven alternatives to
RECORD your work. The NEXT person to own your
airplane will thank you for it.


Bob . . .


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jrevens



Joined: 21 Nov 2013
Posts: 34
Location: Arvada, CO

PostPosted: Fri Jul 08, 2016 11:44 am    Post subject: Re: do I need to change my capacitor Reply with quote

On another internet forum the question was posed - "Why do you need a capacitor on the Rotax charging system?" A reply was posted by another member:

"In our charging systems, the stator produces AC output which goes to the regulator/rectifier. The ouput of that is DC plus an AC voltage on top of it. A capacitor is often used to filter out higher frequency AC ripple on the rectified DC supply. It helps keep the electronics happy and audio quiet."

I'm curious if this is an accurate statement, or not.


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Thorp T-18 N71JE (sold)
Kitfox SS7 N27JE (built & flying)
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PostPosted: Fri Jul 08, 2016 2:58 pm    Post subject: do I need to change my capacitor Reply with quote

-------- Original message --------
From: jrevens
Date:07/08/2016 2:44 PM (GMT-06:00)
To: aeroelectric-list(at)matronics.com
Subject: AeroElectric-List: Re: do I need to change my capacitor

--> AeroElectric-List message posted by: "jrevens" <jrevens(at)comcast.net>

On another internet forum the question was posed - "Why do you need a capacitor on the Rotax charging system?"  A reply was posted by another member:

"In our charging systems, the stator produces AC output which goes to the regulator/rectifier. The ouput of that is DC plus an AC voltage on top of it. A capacitor is often used to filter out higher frequency AC ripple on the rectified DC supply. It helps keep the electronics happy and audio quiet."

I'm curious if this is an accurate statement, or not.

--------
John Evens
Thorp T-18 N71JE (built &amp; flying)
Kitfox SS7 N27JE (building)

Not exactly accurate. There's no AC on the output of the rectifier. There is a ripple of varying DC voltage, which is what the filter capacitor is supposed to smooth. With the current crop of switching style regulators, there *should* be little to no ripple, but there might be some higher frequency noise from the switcher.

Needed? Only you can know for sure.

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PostPosted: Fri Jul 08, 2016 3:04 pm    Post subject: do I need to change my capacitor Reply with quote

At 02:44 PM 7/8/2016, you wrote:
Quote:
--> AeroElectric-List message posted by: "jrevens" <jrevens(at)comcast.net>

On another internet forum the question was posed - "Why do you need a capacitor on the Rotax charging system?" A reply was posted by another member:

"In our charging systems, the stator produces AC output which goes to the regulator/rectifier. The ouput of that is DC plus an AC voltage on top of it. A capacitor is often used to filter out higher frequency AC ripple on the rectified DC supply. It helps keep the electronics happy and audio quiet."

I'm curious if this is an accurate statement, or not.

This statement and similar ones have been
around for a long time. They have a 'ring
of truth' about them. Everybody knows that
capacitors are a hedge against noise. It's
also common knowledge that the higher the
noise frequency, the 'better' a capacitor
works.

This is a simplistic statement that is un-
quantified (how high is high?) and just
how does ripple on the bus figure into
'quiet audio systems'. I did some simple
demonstrations with an SD-8 on B&C's bench
about 20 years ago wherein I MEASURED the
effects upon ripple voltage for both the
battery and the legacy recommendation for
a 'filter' capacitor.

I was unable to support the notion that
the capacitor was a useful addition to the
system. It doesn't hurt anything but I'm
unable to demonstrated that it helps anything
either.

The test-bench under construction will explore
next generation options for PM dynamo rectifier/
regulators. It will also be instrumented adequately
to explore answers to the capacitor question in
more detail with a test report with measured
data.

But based on what I observed 20 years ago and
since, I'm not a big proponent of adding
fat caps to the bus. I may be wrong. If so,
the REAL answer will be in somebody else's
test report wherein it is demonstrated that
some problem was mitigated by addition of
a capacitor. But for now, my inclination is
to suggest that the capacitor is equally
effective in warding off meteor strikes.

To the question in your subject line, what
makes you think the capacitor is bad? Without
evaluation on appropriate instruments, it's
a rather enigmatic device. Of course, if it's
all puffed up, leaking gooey stuff or smelling
bad . . . well . . . yeah. The puppy has gone
TU.



Bob . . .


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