Damn.

I wanted different stepper connectors on my RAMPS
1.4<http://reprap.org/wiki/RAMPS_1.4>,
so desoldered the male headers and soldered the new ones on. I also removed
the male headers for the thermistor connection and replaced them with
female headers.

Now the board won't work. I plug the thermistor into the headers, but it's
not detected. Worse: if I plug any stepper motor driver in anywhere on the
board, it won't boot. That certainly wasn't the case before I did my work.
I've tested with multiple positions and multiple drivers.

One potential additional screw-up: the capacitor at F2 was poorly soldered,
and guaranteed to break a lead if it wiggled. It did break. I re-soldered
it and checked connectivity, but figure I should disclose everything I did
in case it helps.

Any ideas? I'm not that up to speed on electronics, but I can drive a
multimeter. Any tips on figuring out where I missed a layer on a two layer
connection, broke a lead, or shorted something?

 – Garth

On 4/27/12, Garth Kidd <ga...@garthk.com> wrote:

F2 is a fuse, not a cap. Connectivity between its pads is solid.

I've checked the connections between the 1A/1B/2A/2B headers for the
drivers and the matching pins for the stepper motors, and they're fine.
There's also no bridging between adjacent pins, and nothing is shorted to
either the Arduino ground or the 12V ground.

There's also no connectivity from the thermistors on JP7 to the ground
pins, which worries me because the
schematics<http://reprap.org/mediawiki/images/f/f6/RAMPS1.4schematic.png>
show
that all odd pins should ground. They do seem to connect to the other side
of the capacitors (the side without the black line), though, so perhaps the
local ground is working fine.

Checking the black line side (+?), though: I have solid connectivity for
all but the thermistor I need. So, maybe I've stuffed up that one joint.

I still have no idea why the board is failing to boot if I plug in any
drivers.

 – Garth

Power's OK: the board boots from USB power with no drivers plugged in, and
the 12V supply from the PC power supply nearby is fine.

On Fri, Apr 27, 2012 at 10:58 PM, David Lyon <

Taking the board off the Arduino…

The joint looks clean. I can connect through the header to the far side of
the board, so the header itself is OK. Still no connectivity from pin 1 on
JP7 to the - side of C5, though. There's a tiny amount, but it goes up —
much like if there were a capacitor in the way. My multimeter reckons it's
about 16.4uF from pin 1 to C5, but C5 itself measures at 10uF and its
neighbours at 20uF.

This is well beyond my ability to nut out. Any ideas how I can save $80 by
avoiding having to buy a new RAMPS v1.4 kit?

 – Garth

This is an interesting read...

http://www.globalspec.com/FeaturedProducts/Detail/micromo/Thermoplast...
d_Prototyping_Machine/180947/1

Ok, took JP7 off to fix my pin 1 problem, only to make new problems by
destroying the pads: http://forums.reprap.org/read.php?219,130452

Any ideas?

I can't really see sufficient detail around there,  but here's some
pointers.

First, is it actually that bad?  Any chance you can take a more
detailed close up?

The pads rely on the plating from the bottom pad to the top pad. That
implies a good solder joint with solder that wets well up to the top-
side of the board, assuming there is also some plating in the via/
header hole.  How reliable do you think that might have been before
you did your desoldering?  Was there much sign of solder on the
topside?

The pads only have four incoming copper runs from the pour that leads
from the pad on the cap to the pad on the header. The solder mask
prevents the solder flowing over that gap and bridging it better.
Perhaps carefully clearing away some soldermask and tinning the link
between the pad and the surrounding pour will help.

When you put the headers back in, make sure you use a heap of extra
flux, and a heap of solder to let it flow back through the board.  I
don't know what that header plugs into but if you have the chance to
raise the header off the board (ie it doesn't need to be flush with
the arduino headers) and you want some more reassurance that the
joints are good, you can leave it sticking a millimetre or so proud
and check that the solder flows through.

hope that helps

On Apr 29, 10:38 am, Garth Kidd <ga...@garthk.com> wrote:

Thanks, Brett!

I've lifted the pads for THERM0 and THERM1, destroying the paths from
header to capacitor and header to Arduino pin — and, of course, from
capacitor to pin.

I think my best option is to rebuild the thermistors
circuit<http://reprap.org/wiki/File:RAMPS1.4schematic.png> with
three 10µF caps and three 4.7k resistors on some strip-board, with a strip
of cable to the data pins and some conveniently nearby GND and VCC pins on
AUX-4 <http://reprap.org/wiki/File:Arduinomega1-4connectors.png>.

What I'll have to deal with then is that I've blown some/all of my Pololu
drivers by inserting them back to front. Is there a quick way to test these
using just a multimeter? If not, I can hack a test circuit together.

If I don't have enough spare Pololu drivers around to replace my bricks,
resurrecting this board will cost another $50. At that price, perhaps I'll
be better off throwing the board out, buying a
Printrboard<http://reprap.org/wiki/Printrboard>, and
selling my Arduino Mega 2560.

 – Garth