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Ted Noel wrote:
Due to a Mr. Badwrench episode, I
have an engine computer (Eagle 540) that is non-functional. I have
spent the better part of a year trying to get it repaired. American
Engine can't help me, and is not able to make spares.
I have permission to make spares,
and the intellectual property needed to do so. Can anyone refer me to a
shop that can make a small quantity (about 10) without surrendering my
firstborn male child?
Others have interpreted your request to mean that you are looking for a
company that can fabricate the PC boards and that is certainly the way
it comes across. However, I suspect that what you are looking for is
someone who will fabricate the PCB, procure the parts and assemble them
on to the PCB, unless you are planning to do that yourself. The
following discussion assumes that the data you have is accurate and
complete. A couple of missing files, one file that is one version old
and you may have been better off not getting any data.
There are companies called contract manufacturers that can do all of
the above for you. They have the expertise in procuring parts and
assembling the boards. However, it is unlikely that they will be able
to test the boards for you. Also, you may have a hard time getting as
established contract manufacturer to take on such a
project. For most contract manufacturers, this kind of a job is not a
money maker. They do this kind of work for existing clients or
potential clients as a lost leader in the hopes of making real money
for larger runs and long term relationships. A company may be willing
to do the job for you if they have spare capacity and they can pass the
actual costs of initially reviewing and integrating the BOM (Bill Of
Material) to you. If you can find
such a deal, you can forget about the first born child, you will be
handing over the first born airplane to them in addition to the first
born child.
Another option is that you may be able to find an electrical engineer
or technician who is willing to take on the project as a side job. The
cost will be much cheaper than a contract manufacturing company, but
the quality could be anything -- it could be great or it could be
dismal. Are you willing to deal with the consequences if it is the
latter? You are also counting on luck to find such a person as they
are not advertised in the Yellow Pages and there is usually on easy or
independent way to establish their track record.
Last but most importantly, once you have the assembled boards, how are
you going to test them? What are you going to do when the board does
not work? If you connect the board to the engine and the engine fires
up, that
does not mean that the board is working completely. Are all the signal
paths tested? Are all the parameters in acceptable range or are some
at the hairy edge of going out of bounds? Are all the backup systems
working? How do you know?
This is not a HeathKit radio -- your life depends upon the whole thing
working and if you can not fully test the device you are being
extremely
reckless in trusting your safety and even your life to it.
Following is a more in depth list of issues you will face along with
some general information. Believe it or not, this is a partial list
and I am absolutely sure I have missed a few issues. It is most
probably not of much general interest, but for those that want to know
more, here it goes....
Getting the PCB fabricated is easy if you have all the data. PCB data
is in a format called Gerber data, which is basically a specialized
format for describing graphics data that could be easily interpreted by
photo-plotters made by a company called Gerber. Gerber plotters are
long gone, but the format is alive and well. Over the years a number
of variants of the Gerber format have evolved, but a good board shop
usually has tools that can read most of them. A board typically has an
even number of copper layers, two solder mask layers (top & bottom)
and one or two silk screen layers (top and/or bottom). Hand in hand
with certain Gerber variants is an "aperture" file. For some formats,
there is a single aperture file for the whole project. Other times
there a separate aperture file for each Gerber file. Most modern
Gerber formats, however, have the aperture information embedded in the
Gerber file itself and no separate aperture file is needed.
In addition to the Gerber file, there is a NC drill file for a NC
router that describes the location and sizes of all the holes and a
fabrication drawing that calls out the layer orders and identifies
plated/non-plated holes, slots etc. Most experienced designers also
include a specialized netlist file generated from the CAD system as
part of the board fabrication data. The board house uses this netlist
to actually test each and every fabricated board to make sure that it
conforms to the design. This way, if an assembled board does not work,
you can automatically eliminate the PCB as a potential source of the
problem and concentrate on assembly issues or component failures. The
netlist is optional data and if you have not received that, you are SOL.
Depending upon the number of layers, size of the board, number and
sizes of holes and the quality you are looking for or willing to
accept, you can get 10 boards from a couple of hundred dollars to a
couple of thousand dollars. Whether that is more or less than the
value of your first born, that you will have to figure out.
Your real problems begin when you get the boards. You need to install
the parts on them. Do you have a complete and accurate bill of
materials with a VERY STRONG emphasis on accurate. One or two of
missed suffixes and wrong dash numbers can make the difference between
the board working or not working or your running around in circles
trying to figure out what part is supposed to be there. Another major
complication for you is the whole ROHS (Reduction Of Hazardous
Substance) issue, designed to damage the environment in the guise of
protecting it. In a nut shell, manufacturers have been forced to
remove certain "hazardous substances" specifically lead from all
electronics products and replace them with something less reliable and
potentially more hazardous. In order to make their product line ROHS
compliant, many chip and component manufacturers have discontinued a
number of low volume parts and changed the part numbers for other
components even though the new parts are form and function compatible
with the old parts. As you go through the BOM (Bill Of Material) you
may find that a large number of the parts are no longer available under
the given part number. Do you have the knowledge and resources to
research the discontinued parts and select direct replacement parts?
Then there is issue of parts that are discontinued for real (as opposed
to a part number change). How are you going to handle that situation?
All it takes is one part on the board that you can not source and you
are dead in the water. Do you have the knowledge, experience and
resources to design a replacement?
The most frustrating issue that you will face is parts that are
available, but not available to you. Distributors and manufacturers
may not be willing to give you samples since you are not in the field
(no future business prospect) and may not be willing to sell you small
quantities. Major distributors are usually not willing to sell less
than a reel or tube of a part that they have in stock. A reel is
typically one to five thousand parts, while a tube can be anywhere from
20 to 100 pieces. If no distributor has a part in stock, you may be
looking at a fairly large minimum order to get them to place an order
with the manufacturer and then wait 4 to 12 weeks to get the parts.
Are there any programmable devices on the board? Do you have the tools
to program them? Do you have the complete data to program them? I
have seen it far too many times that the fuse settings for a device are
not included in the binary files but rather included in a separate
programming instruction document that never gets transmitted when the
"data" for the device is handed off. Worse yet (and not all that
uncommon) the fuse data for a commonly used part at a company is
standardized and as a result becomes part of the tribal knowledge of a
company that is never written down or formally passed on.
In short, this is a major undertaking. I understand your position and
sympathize with it. You are faced with the loss of use of your
aircraft and a VERY expensive option of replacing the engine. Fixing
the electronics sounds like a simpler way out, but this road is full of
potholes as well and depending upon what is on the board, may actually
be a more expensive and more dangerous than writing off the engine.
Your worst case scenario is that you spend a lot of time and money on
fabricating spares, only to find yourself at a dead end. There is
actually an even worse scenario: You end up with an unreliable system
that you are now the responsible party for but lack the data and the
expertise to get it to be reliable. Think of it as the dreaded
position of "Responsibility without authority." Good luck!
Regards,
Hamid
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