Archive of the former Yahoo!Groups mailing list: ComputerVoltageSources

Hi CVS-ites
i bought one of the CVS PCB's from Mr. Brown. i've decided
(unilaterally) to post a diary of the process of transforming the
project from little bags of parts to a (hopefully) functioning CVS.
First off, the production quality of PCB i received is excellent. The
silk screen is neat and legible, this is CRITICALLY important in a
densely populated layout like this. The PCB material is high quality
and the solder mask is free from any kind of blemish. i tested the
'wetting' behavior of a few pads and it took solder eagerly and evenly.
i have the two SMT converters on hand and i have an ATOMpro28 on order
from BasicMicro. So today i decided to get the rest my parts ordered
from Mouser and to solder the two SMT chips on the PCB.
Before i get to that story ,i want to point out that if you're not
used to posting a Bill of Material order (BOM) with Mouser, ordering
all these parts from them is a pretty significant typing chore, so cut
yourself some time to get it done. However, i recommend that you
exploit a convenience feature that Mouser provides for free...well...
sort of free... You have to register to use it. The registration is
free and if you log in you will be taken to a 'services' page, one of
which is BOM upload. This takes you to a subpage that displays a large
empty text box. Copy the text from the parts list that Mr. Brown
posted in the files section of this group and paste it into a
spreadsheet (i used the ubiquitous and unavoidable, excel) (i can't
vouch for MAC compatibility on this) Pare the spreadsheet down to TWO
columns: Mouser Part Number and Quantity. If you already have some of
the parts the CVS requires or you have different implementation plans
then it will be easiest to delete those rows from the two-column
spreadsheet at this point. Be sure to delete the non-mouser parts (ie
the AtomPro) too. Mouser doesn't carry those. Next, copy these two
columns into a clipboard and open the Mouser BOM upload window. Then
just paste the two columns into text box and The Mouser window will
create a shopping cart for you and populate it with the prices and
stock conditions of the whole enchilada and total the order amount.
From the shopping cart, you can tweak the order further.
Mr. Brown's inclusion of a parts list with Mouser-PN's saved me a lot
of time and my hat's off to him for that considerate inclusion. So now
Mouser has my order and the fate of all my little bags is in the hands
of some UPS driver.
On to those Surface-mounts....
i'm a devoted DIYer and i've built a lot of kits from many makers
(both for myself and for others) but i'm an amateur solderer at best.
Furthermore i'm dyslexic and old enough to have wired a few
point-to-point heathkits in my life. So i have grudge against any
component that's barely larger than a booger especially when it
doesn't even adhere to your finger as well.
Both Grant Richter and Mr. Brown coached me via email a bit and
assured me that even a fat-fingered old dog like myself could learn a
new trick. First off, the SMT scale of the two converters is NOT the
most brutally microscopic version. That helps! ...and the nice 'eager'
quality of the solder mask on the PCB makes the pads almost anxious to
grab the solder.

Grant convinced me that i should get the right tools together and then
go have some fun (some relaxing distraction) before sitting down to do
this for the first time.
So tonight i went to see a movie (a lengthy foreign one with subtitles
and all!) and then i went home and sat down to do this thing...

It was over, neatly and correctly, in time for me to get upstairs in
time learn what Mr. Eric Cartman was up to in South Park . For those
of you unfamiliar with the rhythms of life in Mabuse Manor, that
translates to FIFTEEN MINUTES, start to finish!

Here's how i got this done:
Toolwise:
- you should have a magnifier of some sort for after the fact
inspection. i did the actual work with only my reading glasses on -
pretty much my normal eyesight. But a magnifier is de rigeur to detect
any solder bridges after you're done.
-i use an 'experienced', frankensteined assembly of Weller solder
station parts (WTCP + TCP iron) I did buy a fresh TCP tip, the longest
and pointiest one available at a local store. i favor round point to
flat points but that's a matter of taste.
-It is also a good idea to have some solder wick/braid to clean up a
bridge, if you create one.

At Mr. Brown's suggestion, i wrapped the blade of an Xacto knife with
tape , sticky-side out. This makes a really nice 'handle' with which
to position and hold the SMT chips while you solder. Also at his
suggestion, i soldered two opposing corners first to hold it down,
then i just went slowly and steadily down the line, soldering each
tiny 'foot' with the tip. Like i said, 15 minutes and i didn't have to
wick-up a single bridge.
It wasn't even close to the most challenging solder tasks i've done in
my time. The barest level of soldering common sense and experience is
all that's needed. Use only the tip. Get in with the solder fast. Use
a light touch, and get off fast.
It was MUCH easier than i thought.
Further on in this process i'll learn whether the converters are
perfectly connected but each leg passed a simple VOM continuity test.


While i stubbornly clutch my curmudgeonly prejudice against tiny parts
that are made for the convenience of robots, i will freely profess
that this part of the project was absolutely problem free. It's off to
a good start.
Early kudos to Mr. Brown and thanks to Obi-Wan Richter for massaging
my attitude before i stepped into the ring!

more to follow as i get it done
-doc