Crystal Oven; Test Mode - Codan X-2 Service Manual

Adjustments 7-2
2.

7.4 Crystal Oven

108-04840
The Crystal Oven, on the Rx/Exciter & Control PCB, is attached to the
Reference Crystal Z3
minutes warm-up period. The temperature operates between 50°C to 65°C
and is not adjustable. Replace if the results are outside the specified limits.

7.5 Test Mode

The X-2 Transceiver is provided with a special Test Mode to assist in the
following procedures:
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To select the Test Mode:
1.
2.
3.
104-02908
On the PA PCB:
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+5V regulated DC supply selected in transmit only (IC2) +5 V
± 0.4 V. No test point provided but it can be checked at a number
of places. For example: R11
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Zener shunt controlled DC supply to IC1
This can be checked at pin 5 of IC1.
. The oven should be checked after allowing five
[D3]
Alignment of the 45 MHz roofing filter using only an Oscilloscope, a
Signal Generator and a simple jig made from an 18 Ω resistor and 470
µF capacitor attached to clip leads.
Alignment of the T5 and T6 in the 455 kHz IF circuit.
Checking of VCO1 (not adjustable).
Checking and adjusting of VCO2.
Adjustment of the USB channel frequency.
Adjustment of the LSB channel frequency.
Checking the PA. The band switching, the intermodulation distortion at
the top, bottom, and centre of each filter band.
Adjustment of receiver sensitivity at 15 selected frequencies between
2 MHz to 18 MHz.
Switch off the Transceiver.
On the Rx/Exciter & Control PCB , remove the shorting link parked
on the two ground pins of Link 1 and 2 and fit to Link 1.
Switch on the Transceiver, which is now in the Test Mode.
X-2 Technical Service Manual
or PTC R22 .
[F2] [E4]
(V1) +5 V ±0.25 V.
[C4]
Publication No: 15-02047