26 Feb
2008
26 Feb
'08
7:40 a.m.
Grant,
On a side note, who here would be interested in ultra
high resolution
scans of old computer PCBs? I'm scanning all PCBs at 3200dpi for
archival. Photoshop won't save jpegs that large, but a 1600dpi scan is
only 50MB or so. Some day I plan to release my whole archive.
You mentioned JPEGs. If you are archiving the scans in JPEG format,
try zooming in on bunches of traces or text on the board. JPEG creates
a lot of artifacts.
It may very well be case that a 600dpi scan using lossless compression
will be much cleaner and usable than a 3200dpi scan using heavy JPEG
compression.
Even with 6 mil traces, 600dpi gives you more than 3 pixels per trace.
I've tried a few of my boards using 1200dpi, 8-bit color, and GIF/TIFF,
with results that seemed acceptable.
James Markevitch
26 Feb
26 Feb
7:48 a.m.
It may very well be case that a 600dpi scan using
lossless
compression will be much cleaner and usable than a 3200dpi scan using
heavy JPEG compression.
I question the "much". JPEG uses 8x8 blocks, so a 3200dpi JPEG cannot
lose more information than a 400dpi lossless, and I'm not convinced a
3:2 difference is enough to earn that "much".
/~\ The ASCII der Mouse
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8:15 a.m.
der Mouse wrote:
In terms of overall processing, I suspect that a 400dpi lossless image (TIFF,
GIF etc.) is a lot more efficient (memory, disk, decoding) than the
corresponding 3200dpi JPEG though, despite JPEG's superior compression.
For PCBs I'd be tempted to do a (very) little post-scan processing I think,
just to introduce more blocks of uniform colour and therefore keep the
filesize down.
I've not done much with scanning of (populated) PCBs though, as every scanner
I've tried so far has been rather useless for the task (focus issues, I
suspect - removing the scanner glass and supporting the PCB a more sensible
height above the scan head would likely be a good idea)
cheers
Jules
It may very
well be case that a 600dpi scan using lossless
compression will be much cleaner and usable than a 3200dpi scan using
heavy JPEG compression.
I question the "much". JPEG uses 8x8 blocks, so a 3200dpi JPEG cannot
lose more information than a 400dpi lossless, and I'm not convinced a
3:2 difference is enough to earn that "much". 
8:29 a.m.
der Mouse wrote:
This is PCB ... I really only see about 8 greys needed at most.
I still would stick to any lossless format however.
It may very
well be case that a 600dpi scan using lossless
compression will be much cleaner and usable than a 3200dpi scan using
heavy JPEG compression.
I question the "much". JPEG uses 8x8 blocks, so a 3200dpi JPEG cannot
lose more information than a 400dpi lossless, and I'm not convinced a
3:2 difference is enough to earn that "much". 
27 Feb
27 Feb
10:48 a.m.
At 06:40 AM 2/26/2008, you wrote:
Grant,
I scan all of my boards at 3200dpi 48bit color in TIFF format. I'm
not going to upload any 3.5GB images (one for each side of an S-100
card). If you mail me a hard drive I will be happy to copy them. :
) Its faster to rescan them at 1600dpi 24bit than it is to open and
resave them.
Color scans are needed if you want to have a PCB shop make gerbers
out of your scan.
Grant
On a side note, who here would be interested in
ultra high resolution
scans of old computer PCBs? I'm scanning all PCBs at 3200dpi for
archival. Photoshop won't save jpegs that large, but a 1600dpi scan is
only 50MB or so. Some day I plan to release my whole archive.
You mentioned JPEGs. If you are archiving the scans in JPEG format,
try zooming in on bunches of traces or text on the board. JPEG creates
a lot of artifacts.
It may very well be case that a 600dpi scan using lossless compression
will be much cleaner and usable than a 3200dpi scan using heavy JPEG
compression.
Even with 6 mil traces, 600dpi gives you more than 3 pixels per trace.
I've tried a few of my boards using 1200dpi, 8-bit color, and GIF/TIFF,
with results that seemed acceptable. 
11:20 a.m.
New subject: board scan, design reconstruction (was IMSAI)
Date: Wed, 27 Feb 2008 09:48:10 -0900
From: grant at stockly.com
To: cctech at classiccmp.org
Subject: Re: TTL CPU Re: IMSAI style C&K 7101 switches
At 06:40 AM 2/26/2008, you wrote:
Hi,
Ive been following this, and maybe I can help. Im a professional PCB layout guy in my day
job. With a schematic and a reasonable resolution jpeg of both sides (I doubt there was
mych multylayer back then) I could reconstruct the design fairly quickly. Nobody is
really going to want to go down the road of taking a picture and turning it into a gerber,
it just wont work. Id just input the schematic, duplicate the ref des for all parts, to
get the netlist, eyeball the jpeg for placement and throw it at the autorouter.
Whats on your top 10 list?
(S-100)
CPU card
Dazzler
Byte Blaster
Async card
disk controller card
I could knock those out in a week or two.
Randy
_________________________________________________________________
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Grant,
I scan all of my boards at 3200dpi 48bit color in TIFF format. I'm
not going to upload any 3.5GB images (one for each side of an S-100
card). If you mail me a hard drive I will be happy to copy them. :
) Its faster to rescan them at 1600dpi 24bit than it is to open and
resave them.
Color scans are needed if you want to have a PCB shop make gerbers
out of your scan.
Grant
On a side note, who here would be interested in
ultra high resolution
scans of old computer PCBs? I'm scanning all PCBs at 3200dpi for
archival. Photoshop won't save jpegs that large, but a 1600dpi scan is
only 50MB or so. Some day I plan to release my whole archive.
You mentioned JPEGs. If you are archiving the scans in JPEG format,
try zooming in on bunches of traces or text on the board. JPEG creates
a lot of artifacts.
It may very well be case that a 600dpi scan using lossless compression
will be much cleaner and usable than a 3200dpi scan using heavy JPEG
compression.
Even with 6 mil traces, 600dpi gives you more than 3 pixels per trace.
I've tried a few of my boards using 1200dpi, 8-bit color, and GIF/TIFF,
with results that seemed acceptable. 
11:40 a.m.
New subject: board scan, design reconstruction (was IMSAI)
On Feb 27, 2008, at 2:20 PM, Randy Dawson wrote:
Hi,
I think that what Grant has been going for is authenticity. Back
then, the definition of "rip-up and reroute" was when you reached up
to rub your eyes only to find a dozen or so pieces of red layout tape
stuck to your shirt sleeve and not to the mylar on the light table
(been there, done that). If you look at Grant's site to see what type
of reproductions he has done already, you can get a better sense of
why these scans are so important.
-Mardy
Date: Wed, 27 Feb 2008 09:48:10 -0900
From: grant at stockly.com
To: cctech at classiccmp.org
Subject: Re: TTL CPU Re: IMSAI style C&K 7101 switches
At 06:40 AM 2/26/2008, you wrote:
Hi,
Ive been following this, and maybe I can help. Im a professional
PCB layout guy in my day job. With a schematic and a reasonable
resolution jpeg of both sides (I doubt there was mych multylayer
back then) I could reconstruct the design fairly quickly. Nobody is
really going to want to go down the road of taking a picture and
turning it into a gerber, it just wont work. Id just input the
schematic, duplicate the ref des for all parts, to get the netlist,
eyeball the jpeg for placement and throw it at the autorouter.
Whats on your top 10 list?
(S-100)
CPU card
Dazzler
Byte Blaster
Async card
disk controller card
I could knock those out in a week or two.
Randy
Grant,
I scan all of my boards at 3200dpi 48bit color in TIFF format. I'm
not going to upload any 3.5GB images (one for each side of an S-100
card). If you mail me a hard drive I will be happy to copy them. :
) Its faster to rescan them at 1600dpi 24bit than it is to open and
resave them.
Color scans are needed if you want to have a PCB shop make gerbers
out of your scan.
Grant
On a side note, who here would be interested in
ultra high
resolution
scans of old computer PCBs? I'm scanning all PCBs at 3200dpi for
archival. Photoshop won't save jpegs that large, but a 1600dpi
scan is
only 50MB or so. Some day I plan to release my whole archive.
You mentioned JPEGs. If you are archiving the scans in JPEG format,
try zooming in on bunches of traces or text on the board. JPEG
creates
a lot of artifacts.
It may very well be case that a 600dpi scan using lossless
compression
will be much cleaner and usable than a 3200dpi scan using heavy JPEG
compression.
Even with 6 mil traces, 600dpi gives you more than 3 pixels per
trace.
I've tried a few of my boards using 1200dpi, 8-bit color, and GIF/
TIFF,
with results that seemed acceptable.
28 Feb
28 Feb
12:23 p.m.
New subject: board scan, design reconstruction (was IMSAI)
Hi,
Ive been following this, and maybe I can help. Im a professional
PCB layout guy in my day job. With a schematic and a reasonable
resolution jpeg of both sides (I doubt there was mych multylayer
back then) I could reconstruct the design fairly quickly. Nobody is
really going to want to go down the road of taking a picture and
turning it into a gerber, it just wont work. Id just input the
schematic, duplicate the ref des for all parts, to get the netlist,
eyeball the jpeg for placement and throw it at the autorouter.
There are hundreds of shops that do exactly what I said, take an
image and make Gerber files. They do it using the help of
specialized CAD software and calibrated scanners. Not all of the
process is automated. The average S-100 card takes them an hour or
two. The Kenbak board took them about half a day! I have had all of
my scans done by Mile High Testing. They will take a high resolution
1000-4000dpi image and turn it into accurate Gerber data. I pay
extra to make sure my traces and silk screen are just as ugly (or
pretty) as the vintage boards. Normally they would just image the
two copper layers and throw reference text onto the silk screen.
http://www.mhtest.com/scanning.shtml
They use expensive equipment from ScanCAD International.
http://www.scancad.com/index.php
The service is pretty affordable too. It only cost me about $500 to
scan the 10x16 Kenbak PCB, and I can hold the vintage Kenbak PCB to
the reproduction and see light through every single via. : )
S-100 cards with a silk screen are about $300 to $350 each. The
presence of a silk screen even if they are not creating silk screen
Gerber files increases the price. It causes more after the scan work
for the operator because the computer recognition software has a hard
time looking through the silk screen. This is where Mile High
Testing stands above the rest of the competition. They were the only
company who promised me my boards wouldn't be destroyed. Most of the
other companies want to scan the board and then sand all of the silk
screen off of the copper traces to get a green on bright copper
finish. Contrast like that improves the software's work.
MHT also had the most reasonable pricing. I can say they do perfect
work after getting close to 20 boards scanned! I have also not had
any problems getting PCBs made out of these Gerber files. I was
worried that a plotter might have a problem with a several MB file,
but no problems yet! : )
Grant
6142
days inactive
6144
days old
7 comments
7 participants
participants (7)
-
bfranchuk＠jetnet.ab.ca -
grant＠stockly.com -
jam＠magic.com -
jules.richardson99＠gmail.com -
mardy＠voysys.com -
mouse＠Rodents.Montreal.QC.CA -
rdawson16＠hotmail.com