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