[NLRS] DB6NT assembly progress

[Doug Reed]

I bought one of the DB6NT 10 GHz transverter kits that Jon delivered last
Saturday. There are a few more kits out there and a number of people were
asking how hard it is to assemble. So I'll do a quick review of my progress
to date. 

Monday night I spent about 2 hours slowly and carefully assembling the tin
plate box and soldering the PCB into the box. Thankfully the end of the box
was already punched for the connectors or it would have been a lot harder.
I used a bench grinder to remove maybe 1/32" on the end of the long wall on
the box. This gave it enough room to fit together in the top and bottom
plate while I soldered the side seams. 

I then used a sheet of sand paper on a flat surface to take a bit off the
edge of the PCB so it would fit in the box. I also rounded the corners of
the PCB a little to match the short radius corner of the tin plate box
itself. And I sanded off a little bit more on the edge where the double
thickness of metal is in the side plates. This "pruning" is all according
to the assembly instructions..... GO SLOW! You don't need to take much and
if you go hog wild you may remove so much that traces short to the side
wall.....

I then installed the SMA connectors so I could position one end of the PCB
on the connector pins. I maintained the same height all the way around the
enclosure while soldering the PCB to the side walls. I used liquid flux to
aid the soldering but in reality, the tin plate box and plated PCB solder
together very well. 

I also installed the feed-thru caps. They could have waited but it really
didn't make much difference. The manual says to do them later. 

Tuesday night I spent about 2.5 hours installing all the components on the
top side of the PCB. I HIGHLY recommend that you have all the top parts
installed before mounting any surface mount components. SMT parts will
crack if the PCB flexes and for some of the top side parts, force may be
required. 

On the 56 ohm dummy load resistor, I formed the leads so it was held off
the PCB by about 1/16" so it is less likely to burn the PCB. 

I never thought of soldering voltage regulators to the PCB for heat
sinking, but it should work. The regulator on the side wall is taller than
the wall itself. Instead of trying to trim the thickness of the leads, I
just cut off the excess part of the tab before I soldered it in place. I'm
afraid that trying to shave the lead could damage the internal connections
to the regulator. 

The jumper wire to carry 12 volts to the second regulator isn't obvious on
the drawing. Don't forget it. 

The pipe cap filters soldered together easier than I thought. The caps are
silver plated so it was easy to tin the rim of the cap. Take care not to
get solder on the INSIDE of the cap, it will lower the Q of the filter.
That is also why the manual says to be careful to make sure the coupling
pins are vertical when soldered. 

I carefully centered the cap within the ring of plated ground holes before
I applied heat. Again, I was surprised how easily the soldering iron heated
the whole cap to melt the solder. When it did, I added more solder to the
outside edge to form a strong fillet to mount the cap. The directions say
to put a screw in the cap and then apply heat to the screw. I just put the
iron on the cap about midway between the hole and the edge of the top. Just
be SURE you don't get any solder into the threaded hole! If you are
careful, the small amount of solder added on the top of the cap for heat
transfer will not interfere with the screw or lock nut. 

You will need a little extra space while soldering the cans of the various
coils to the ground plane. It is easier if you do the cans before you put
the crystal parts on the board. 

The trickiest part of the assembly was when I was looking for the 22pf
capacitor for the crystal oscillator. Low and behold they supplied an 18pf
and 4.7pf cap which adds up to 23pf but isn't mentioned in the
instructions.... 

Don't forget to solder the crystal can to the little ground tab under one
corner. This adds a couple kinds of stability to the oscillator. 

The PTC resistor crystal heater components are not provided but Digi-key
sells PTC resistors so I'll be adding that to mine anyway..... And a little
chunk of styrofoam peanut for insulation....

----------------

Due to various commitments the rest of this week, it will probably be next
Monday before I get around to soldering SMT components on the PCB. After
that I should be ready for tune-up..... We'll see what happens.

73, Doug Reed, N0NAS.