[hpsdr] Hermes build report

[Oliver Goldenstein]

Hello to the list !

Like Rob i want to share my experiences building my own Hermes SDR from
scratch. I hope it will be useful for others and may give others a kick to
start their own.

Befor the Hermes i built successfully several Softrocks, a MoBo Transceiver
and the latest the UHFSDR. The UHFSDR was the first one fully built out of
SMD's which i soldered by hand.

With the Hermes i wanted to try the reflow method using a normal kitchen
oven with 1500 Watts and 250 deg C. Before starting with the hermes i
successfully reflowed several little boards i had around and never finished.

Some results you may see here:

http://hermes-sdr-build.blogspot.de/2012/12/smt-reflow-soldering-first-try.html

Just a quick note to the first picture. This method i had to use later to
solder the ADC LTC2208, because while using my stencil i did not get
sufficiant solderpaste on top of the board. It worked.

You do not need a expensive reflow controller. I used a multimeter with a
temperature sensor and learned how to drive the reflow profile manually.

http://hermes-sdr-build.blogspot.de/2012/12/smt-reflow-soldering-preparing-oven.html

I then began to sort all about 540 parts i got from Digi-Key and others. I
bought little boxes and began to unpack and sort every part!

At least i had a hill of 10 Boxes:

http://2.bp.blogspot.com/-6F9zr-pq-YE/UQLRfRzvQoI/AAAAAAAABy0/klN8WUXlknw/s1600/IMG_20130125_174128.jpg

Very handy are the digikey labels which i cut off at the edge and glued
them in every box.

To populate the solderpaste on the board using my stencil was the most
critical process:

http://hermes-sdr-build.blogspot.de/2012/12/hermes-sdr-board-stencil-arrived.html

Maybe i did something wrong with the pressure i used to press the paste
through the holes, or the stencil was not cut at every hole. i do not know.

Result was, that at the FPGA and LTC2208 (the most expensive parts) i had
nearly no paste at the side legs. At the LTC2208 nearly nothing. I decided
to move further and put some paste manually at the LTC2208 legs.

I only placed all IC's, the MiniCircuit Parts, LED's with resistors and all
Diodes on the board. That took about an hour. I had fear, that my solder
paste gets too dry and decided
 to burn the board.

Four minutes later i had a result:

http://hermes-sdr-build.blogspot.de/2013/01/success-with-baking-pcb.htm

An initial inspection brought several solder joints at the LTC2208 which
where easy to remove with solder wick and a good flux. That was easily
solved.

All other parts where ok, except the FPGA which was not soldered at on side
( north of the board ). I thought: "... that is easy, i saw this several
times on youtube !"
My plan was to drive along the legs and solder leg after leg.

Oh man, what a mistake. That was not that easy than i thought before. I
bent several legs and soldered them together. My heart began to pulse and
my head became red. I thought: " that was it. All damaged !"

The operation to solve that disaster took me two hours. First of all i
removed all solder with a lot of flux and solderwick. Next i placed the
board just in front of my head and and with a four times magnifier and two
little fixing pins from my wife i recurved leg for leg on the north side of
the FPGA. You should have seen my smile, when i finished that. Oh man.

The rest was easy.

The only  documents i used where the schematics and the BOM and the Tapr
HIRes Photo.

At least i forgot to solder one side of R74 which prevented the board from
starting.

You may think, what a mess. But maybe some others will give the build a
try.

It is doable.

In my opinion good eyes and a good magnifier are the key.

Give it a try and report your results.

If you have questions, feel free to ask me.

Many thanks goes to the Project Team and the List.

I enjoyed the built ( most of the time :-) and i enjoy my little
transceiver with this impressive cuSDR Software.

Thanks Guys!

73 Oliver DL6KBG

http://youtu.be/_VVpdW4GQiY

F
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