Date: Sun, 23 Sep 2007 12:30:27 -0500
Reply-To: Leslie Schwartz <lhs_emf@PACBELL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Leslie Schwartz <lhs_emf@PACBELL.NET>
Subject: Re: ECU firmware location
In-Reply-To: <817990.98663.qm@web82703.mail.mud.yahoo.com>
Content-Type: text/plain; charset="US-ASCII"
Guys,
Reverse engineering an old control pcb is (can be) a very tough project.
If it is at all possible to get them, getting a system level diagram and an electronic schematic might make the project possible.
I do not know what technologies may have been involved in this control board. For example, there may have been an EEPROM; which is a
programmable device, that obviously would run a control program that the control system needs to carry out the functionality.
Sometimes you can find out the device type, buy a programmer and create copies of that programmable device, sometimes this is not
possible. And really if that is the case it would be easier to take the system level diagram and the "test bench mechanical data"
and recreate the control functionality with a new control design. Remember that you need to know the input / output voltage (and
current) ranges for all of the involved functions, you have to know sequencing of the control functions, etc.
The EEPROM program can sometimes be re-optimized by writing a new program or altering the old one; but you need to know if there are
micro-processors involved, their architecture, their assemble code, registers, i/o, etc. Sometimes getting these parts is very
expensive, they become scarce and expensive, it can takes months of research to find an old part.
You may have already discussed this in depth, so excuse me please if I am going over points that have already been made.
But practically speaking, buying a few spare boards to make this sort of investigation and reverse engineering possible, it pretty
trivial; consider that along with that there is the task of getting a "lab - test bench set up" hand tools, electronic test bench,
auto engine test system, along with the above needed engineering design data are essential to make this project feasible.
If the system functions are simple enough you may be able to deduce them and create a new design which may be easier altogether;
otherwise it's a very tough project. I have not seen this pcb so I don't know for sure. But this is one of those projects that can
be done by a small engineering firm which is set up to do this work and which has the background experience from some previous
parallel assignments.
Just one idea that popped into my brain, if you can NOT get the engineering data for this old system; but know what it interfaces
into on the old engine, get a more modern control board for an engine system in production where all of the data is available, use
that new board, re-program it as needed, and create a control inter face adapter - electronics and electro mechanical to make the
new board interface to the old engine.
Leslie
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of David Kao
Sent: Sunday, September 23, 2007 12:34 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: ECU firmware location
I agree. It's hard without a schematic and the PCB is covered with
a protective paint makes it even harder. For low value (resistance)
resistors you can measure them without pulling their leads off. If the
values are high you can compare your measurement with the spare.
This usually is good enough to find bad resistors. For capacitors
you can use the ohm measurement of an analog VOM to check them.
Capacitors will show charging and discharging behavior. By looking
at how the needle swings you can tell if the capacitor is at least
doing what it should do. Can't tell if the value is correct though.
Catalytic capacitors are the most likely ones to go bad. There should
be only a few of them on your ISCU.
If you have a spare you will feel less risky to turn on your solder
iron. I have seen people who are trained to repair surface mount
PCBs. They are very good in removing and installing parts on very
high density PCBs. If you have similar skill like theirs it is probably
safe to repair your ISCU. But of course you will need to isolate the
defective component. That is the hardest part.
Now that your ISCU is an European breed. I can see why you want to get
it fixed instead of replaced. If you can identify the defective part
It will probably take less then 15 minutes to repair it.
Not trying to tell you how good I am. Just some experience I had. Leslie
is pretty good. He will have some more ideas I believe. Yes, a good
magnifier is a must. Good lighting is definitely needed. A small piece
of damp sponge for cleaning the tip of the solder iron is a must too.
Good luck.
David
--- tinker man <tinkerman007@GMAIL.COM> wrote:
> On 9/23/07, David Kao <dtkao0205@yahoo.com> wrote:
>
> > Try to measure each resistor on the PCB. They tend to change value because of
> > aging and heat.
>
> Pretty hard in my case, with close to 200 parts on the PCB, all
> affecting each other's measurements...
> I was also checking the capacitors, which are more problematic.
> The good news is that I might get a spare unit for comparison and
> testing. I'll keep my fingers crossed till I get it...
>
> Cheers,
> TM
>
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