DFD4 / DFD4A assembly instructions.

(DFD4A has no offset capability and is for test equipment only)

DFD4j1.jpg (27586 bytes)

DFD4a.jpg (10288 bytes) Begin by placing solder globs on the four rectangular

pads for the surface mount TCXO.

DFD4b.jpg (11201 bytes)
Carefully Position the TCXO with pin 1 as shown and
remelt the solder globs while pushing down on
that side of the device until all four pads of
the TCXO are soldered.  You can check
by looking at the edge view to verify that
solder has flowed onto the TCXO terminals. 
If later the unit shows only 8 black squares
on the display it may be because one or
more of these terminals
did not properly reflow solder.
DFD4c.jpg (19431 bytes) Next mount the IC sockets and display header.
DFD4d.jpg (32871 bytes)
Next install and solder all resistors and the two
back to back diodes.
DFD4e1.jpg (6408 bytes)
Then install and solder all capacitors and the
78L05 voltage regulator.
DFD4f.jpg (20743 bytes)
Then the two 2 pin headers.  The one next to the
18 pin socket is always installed. 
The one next to the 8 pin socket is installed
only if you DO NOT intend to use it as test equipment.
DFD4g.jpg (12981 bytes)
On the back side of the PCB install and solder the
10K contrast control (adjust it fully CCW)
and the 25K calibration control.
Later when assembly is complete calibration
consists of connecting the unit to a known
accurate frequency, or by zero beating the TCXO
against 20MHz WWV, and  adjusting this 25 turn pot.
DFD4h.jpg (32656 bytes)
Next install the green 15 turn trimpots. 
(these are not included or
used with DFD4A).
Install the fourth trimpot if DFD4 is NOT
going to be used as test equipment.

DFD4i.jpg (11257 bytes)

Mount the 14 pin female header on the display
module soldering only one pin. 
Then verify the connector is at a right angle to the
module, remelting the soldered pin and adjusting
the connector if necessary. 
Then solder the remaining pins.
Plug the module into the DFD4 PCB.


At this point you can plug the counter board into
the module and power them with a 9 volt battery.
You should see something displayed momentarily
such as "FAST HF" then a frequency. 
What you see at this point is not important as some
inputs are still floating until final assembly in your
If so, you are ready to proceed to final assembly
in your enclosure.
When used as test equipment, wire the unit to
the external controls
using the connection diagram below.


DFD4k.jpg (45337 bytes)










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