User Manual
18
UM-20 Low-cost Oven-controlled Crystal Oscillator (OCXO) Assembly
Use in SRS DS345
Installation
We installed the assembled OCXO module with OCXO131-40 S/N
2302-1000 into a SRS DS345 synthesized function generator. This
unit was configured at the factory without Option 02 (Internal
OCXO).
Since the Pumpkin OCXO module was not designed for use in the
DS345, we had to find a robust way to mount it. We found that in
the DS345’s rear corner where the various back-panel BNCs are
located, there is enough room to locate one of our modules by
mounting it to one of the sides of the aluminum sheet metal
chassis. We machined two countersunk 82º holes sized for 4-40
flathead screws 1.500” apart, 0.325” from the top edge of the
chassis.
Figure 7: OCXO PCB assembly installed in DS345
The DS345 maintains a chassis ground that is separate from
(digital) ground; since the OCXO module Rev A PCBs connected
the four 4-40-size standoffs to (electrical) ground, we had to isolate
these modules when used in the DS345. The solution was to use
nylon screws, along with nylon washers in the top two mounting
holes.
9
9
The OCXO module’s lower two captive standoffs simply had the nylon screws
screwed into them until them bottomed out; the net effect is that they form a
captive spacer that insulates the lower standoffs from the DS345’s chassis.
Nylon 4-40 screws and
washers for mounting
OCXO Module Rev A to
DS345 chassis
5-wire 22AWG twisted
harness to 7-pin 0.100”
pitch connector on
DS345 top board
(at right)
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