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'[EE] Reverse Engineering legacy PCB boards'
2006\11\05@154342 by Mauricio Jancic

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Hi,
       I have two boards from a customer who wants me to produce identical
replacements. This are 10+ years old boards (Stepper controller) with a
bunch of logic, comparators, and some other parts. No microcontrollers.

       I would like to know if there is a set of tools available to
reproduce as exactly as posible a board, in order not to have to follow all
the traces with the multimeter and the make the schematic.

Any ideas?

Regards,

Mauricio

2006\11\05@160115 by peter green

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>        I would like to know if there is a set of tools available to
> reproduce as exactly as posible a board, in order not to have to
> follow all
> the traces with the multimeter and the make the schematic.
how many layer is the board? if its only a double sided board then i presume you could depopulate it, scan it and trace the scans.

circad seems to offer the ability to put your scan up as a background image so you can trace it (http://www.holophase.com/reverse.htm)

if its more than two layers you have the problem of getting scans of all the layers


2006\11\05@161316 by Bob Axtell

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Mauricio Jancic wrote:
> Hi,
>        I have two boards from a customer who wants me to produce identical
> replacements. This are 10+ years old boards (Stepper controller) with a
> bunch of logic, comparators, and some other parts. No microcontrollers.
>
>        I would like to know if there is a set of tools available to
> reproduce as exactly as posible a board, in order not to have to follow all
> the traces with the multimeter and the make the schematic.
>
> Any ideas?
>
> Regards,
>
> Mauricio
>
>  
Nope.

--Bob

2006\11\05@192655 by Bob Axtell

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Bob Axtell wrote:
{Quote hidden}

OK, here is about all you can do:

Build or buy a very low ohmmeter; this is designed to deliver a voltage
across the probes of no more that 100mV.
Routinely probe every OTHER point against one point. This will take a
LONG time, possibly a week if it is more
than 2 layers. A normal beeper will NOT do, and MIGHT damage a
component, too.

If you can remove all of the components without damaging the PCB, you
can hook every pin up to a raw PCB tester
and "learn" the PCB. This little trick can be expensive, but MIGHT save
time.

Once you have a reliable schematic, then verify the values of
everything, and of course the digital devices. Be aware
that even when the exact PCB is created, it might not work because  HC
devices have become MUCH more sensitive
to noise that they were 10 years ago.

Be sure to quote it high.

--Bob

2006\11\05@222952 by Ray Newman

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Boy do I wish there was.
I have done the same from time to time  to "follow all the traces with a multimeter to make the  schematic" .
Not easy but it all depends on how many parts and hopefully
ALL the parts are labeled.
Hopefully you can charge the customer enough to make it worth your time.

Ray



On Sun, 5 Nov 2006 17:43:36 -0300, Mauricio Jancic wrote:
{Quote hidden}


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(decoded 7bit)

2006\11\06@010541 by John Chung

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Why don x-ray the board and do less probing? For
multilayer 4> x-ray may not be a good option.

John

--- Ray Newman <spam_OUTlistTakeThisOuTspammicrodesigns.biz> wrote:

{Quote hidden}

> > -

2006\11\06@013255 by picmully

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As mentioned, the best place to start is a bare board. Given that, I
recommend that you hire a board population house to remove the parts -- with
the minimum of damage.

The rest is grunt work. Route one side of the board, flip (mirror) the
result, then route the other side to match. This recommendation is based on
the circuit's description and age, which suggests a 2-sided, through-hole
design.

Shawn


{Quote hidden}

2006\11\06@014713 by William Chops Westfield

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>  I would like to know if there is a set of tools available to
>  reproduce as exactly as posible a board, in order not to have to
>  follow all the traces with the multimeter and the make the
>  schematic.
>
Well, there are probably "companies of questionable morality" that
will happily reverse-engineer a board and sell you lots of copies.
Strictly speaking, it may be easier to go photographically direct
from the existing boards to new boards without doing the useful
step of deriving the schematic.  After all, PCB manufacturing is a
photographic process.

Depending on the complexity and "strangeness" of the board, you can
probably use a combination of the traces, chips, and what you know
the circuit should look like to reverse engineer the board pretty
quickly; use a standard CAD package and a parts library that is set
up to correspond to physical reality, and see if the PCB you get looks
like the one you have.  Later, you can replace parts with more normal
schematic symbols.

BillW

2006\11\06@014756 by Ruben Jönsson

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Hello,

If it is all legal, that is if your customer really does own the design, he
should be able to give you schematics and BOM of it. The board manufacturer
could have gerber files left from the last time it was produced. Somebody has
to have built it and they should have BOM, component placement drawings and
possibly also schematics.

/Ruben

{Quote hidden}

> -

2006\11\06@020654 by Shawn Mulligan

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One of my current clients is clearly the owner of their design, but after 20
years, they are left with only bits and pieces of the original IP --
schematics, code, etc. Good for a consultant -- bad for a company.



{Quote hidden}

2006\11\06@025541 by James Nick Sears

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Are 100% of the parts still available in fully package/pin-compatible  
form?

-N.


On Nov 6, 2006, at 2:06 AM, Shawn Mulligan wrote:

{Quote hidden}

> -

2006\11\06@030641 by Shawn Mulligan

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Good point... and if they are, for how long? Often the cost and difficulty
of obtaining old parts justifies a re-design. Shawn




{Quote hidden}

2006\11\06@033028 by Tomas Larsson

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I would have thought that most PCB-Cad sw do dxf-import, then it would be a
quite easy taskt to scan the board, use some DTP-Sw to convert from tiff to
dxf and import it to the pcb-software.
I know that Corel-Draw easily could convert from tiff to dxf.

With best regards

Tomas Larsson
Sweden
http://www.tlec.se
http://www.ktl.mine.nu
http://www.naks.mine.nu for downloads etc.
ftp://ftp.servage.net for uploads use "naks" as both password and username.
Or you can use the free http://www.yousendit.com service.

Verus Amicus Est Tamquam Alter Idem

>

> {Original Message removed}

2006\11\06@061028 by Mauricio Jancic

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> If it is all legal, that is if your customer really does own
> the design, he should be able to give you schematics and BOM
> of it. The board manufacturer could have gerber files left

It's not hes design. And I'm not sure if it legal. The problem is that the
company that manufactured the board went of bussiness and the are no
replacements on the market.... I think it’s a good reason to copy the board.

Mauricio

> {Original Message removed}

2006\11\06@061043 by Mauricio Jancic

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> Be sure to quote it high.

Done! :)

Mauricio

2006\11\06@061253 by Mauricio Jancic

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> Boy do I wish there was.

I was refering to the technic that Peter Green mentioned at the beginning.
The trick is to place a scanned image of the board on the schematic and then
place the traces on to. That would provide some simplicity to the work.

Mauricio

2006\11\06@061553 by Mauricio Jancic

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Yes, they are. The most different one, one that is on a ceramic DIP case,
now has a plastic case. The other parts I can get.


Mauricio Jancic
Janso Desarrollos
http://www.janso.com.ar
.....infoKILLspamspam.....janso.com.ar
(54) 11-4542-3519


> {Original Message removed}

2006\11\06@061635 by Mauricio Jancic

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He just want a set of 3 boards of each so he doesn't have to replace all the
machine electronics.

Mauricio Jancic
Janso Desarrollos
http://www.janso.com.ar
EraseMEinfospam_OUTspamTakeThisOuTjanso.com.ar
(54) 11-4542-3519


> {Original Message removed}

2006\11\06@064956 by D. Jay Newman

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> > If it is all legal, that is if your customer really does own
> > the design, he should be able to give you schematics and BOM
> > of it. The board manufacturer could have gerber files left
>
> It's not hes design. And I'm not sure if it legal. The problem is that the
> company that manufactured the board went of bussiness and the are no
> replacements on the market.... I think it’s a good reason to copy the board.
>
> Mauricio

Under US copyright law it's a good reason to make a compatible board.

And if you're not sure that it's legal, then I suggest that you either
cut and run or get something in writing from your employer that covers
*all* your legal expenses in case of a, er..., misunderstanding.

Besides, if it's 10-20 years old, then it would probably be easier
to do a clean-room design than to blindly copy an old board.
--
D. Jay Newman           ! Author of:
jayspamspam_OUTsprucegrove.com     ! _Linux Robotics: Building Smarter Robots_
http://enerd.ws/robots/ !    "A backward poet writes inverse."

2006\11\06@082121 by Alan B. Pearce

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>how many layer is the board? if its only a double sided board then i
>presume you could depopulate it, scan it and trace the scans.

Not quite, after depopulating it, you polish it so the copper is bright, and
get the board house to photograph it to make the master. Agree it is really
only practical with a 2 layer PCB, but not impossible on a multilayer one -
if you have some suitable milling machinery to skim the layers off.

2006\11\06@085727 by Tony Smith

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> > Boy do I wish there was.
>
> I was refering to the technic that Peter Green mentioned at
> the beginning.
> The trick is to place a scanned image of the board on the
> schematic and then place the traces on to. That would provide
> some simplicity to the work.


That's a tried and true method for copying a board, remove all of the
components and put it on a scanner.  For a single-sided board you could even
skip the unsoldering phase.  

Clean up the scan and make a transparency.

It's probably only worthwhile if you only need a few boards (you need to
drill them by hand etc) or you have lots of patience.  (try toner tranfer!)

Still, the occasional pirated board surfaces with the original manufacturers
logo (in copper) on it, so it is possible to do a decent product run this
way.

Tony

2006\11\06@092357 by Tamas Rudnai

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That's exactly what I was thinking of initially, however, first you may have
a photo from the solder stop layer as well, and then you will not have a
schematics so you can't test the device what's going on if some adjustments
needed during it gets alive (varcaps, potmeters etc, where and what to
measure etc). Also mentioned here by Bob that some components could have
different sensitiveness for noise nowadays other than was it before so that
may need some changes in the circuit or at least different values needed for
some of the components.

I would say if the purpose of the board is well known, what should it do,
what are the expectations/limitations etc maybe better to design a
replacement board with the very same dimensions and interface and forget the
old one completely.

Tamas


On 06/11/06, Alan B. Pearce <@spam@A.B.PearceKILLspamspamrl.ac.uk> wrote:
{Quote hidden}

> -

2006\11\06@102736 by alan smith

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personal experiance...thats not always true.  Things get lost.....or damaged or destroyed.  I agree...quote high....or by the hour, and bill weekly.  Or ask for an escrow retainer up front to draw against.

Ruben Jönsson <KILLspamrubenKILLspamspampp.sbbs.se> wrote:
If it is all legal, that is if your customer really does own the design, he
should be able to give you schematics and BOM of it. The board manufacturer
could have gerber files left from the last time it was produced. Somebody has
to have built it and they should have BOM, component placement drawings and
possibly also schematics.



---------------------------------
Cheap Talk? Check out Yahoo! Messenger's low PC-to-Phone call rates.

2006\11\06@104324 by Alan B. Pearce

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>first you may have a photo from the solder stop layer as well,

The solder mask was often done by having a master with the pads on and
producing a defocused photo of it, and the amount of out of focus enlarged
the pad size sufficient for the solder mask.

This was easy to do when doing double sided PCBs, as the master could be
exposed in a colour that showed only the black pads, and ignored the red and
blue tapes.

However from the ongoing discussion from the OP, it sounds like his client
wants to manufacture some PCbs to use as spares in machine repair, so the
number of boards is limited and I wouldn't worry about a solder mask - but
is the original PCB does have a solder mask, I guess it could be recovered
photographically before polishing it off.

2006\11\06@104606 by Ruben Jönsson

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Perhaps you can get the original specifications for the design and work from
there. After all, it is easier to know that it works if you know how it should
work, especially if you have to change obsolete components. Why was that
component selected in the first place? What rating is needed? etc..

Your client also should know the criteria for how he will verify and validate  
the design. What are those? (Which should be the specifications in the first
place.)

/Ruben

> One of my current clients is clearly the owner of their design, but after 20
> years, they are left with only bits and pieces of the original IP -- schematics,
> code, etc. Good for a consultant -- bad for a company.
>
>
>
==============================
Ruben Jönsson
AB Liros Electronic
Box 9124, 200 39 Malmö, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
RemoveMErubenTakeThisOuTspampp.sbbs.se
==============================

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