36 lines
1.6 KiB
Plaintext
36 lines
1.6 KiB
Plaintext
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Date: 2 February 1985
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From: Headquarters, Indiana Wing/DC
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To: Azden PCS-300 Owners
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Subj: Adjustment of PCS-300 PLL
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One of our members recently experienced a problem with his Azden
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PCS-300 handheld VHF transceiver. The problem appeared to be a
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failure to transmit for more than a second or two at the
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beginning of each transmission. In actuality, the radio was
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transmitting but the frequency was slowly drifting up to about
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151 MHz.
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After some correspondence with the U.S. distributor of the radio,
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the following cure was found. The problem is caused by a
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misalignment of the VCO in the PLL circuit.
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There are 3 circuit boards in the PCS-300. Of course, the one
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you want is the most difficult to get at, the one in the middle.
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To get at the correct board, first you must remove the cover.
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Then you must remove 4 screws, 2 at the bottom of the radio,
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underneath the battery pack, and 2 more near the top of the radio
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between the top circuit board and the heat sink. This will
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enable you to separate the radio, but the plug-in cable to J101
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is quite short and must remain connected for you to make the
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required measurements. If you will turn the front panel
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counterclockwise about 1/8 turn, you should be able to get at
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transformer T104 which is quite close to R137. The top exposed
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end of R137 is TP103.
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1.) Turn power on and connect digital voltmeter to TP103.
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2.) Set frequency of radio for 142.000 MHz.
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3.) Adjust T104 until voltmeter reads 1.00 volts plus or minus
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0.3 volt.
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