The following provides a more useable range af the RF attenuator by re-allocating stage gain at the first and third IF. This change allows the use af less front end attenuation, allowing you to hear the desired signal while reducing interfering signals during CW contests and pine ups.
Caution:
This change requires advance surface mount soldering equitment that is rated for CMOS circuits. It also requires farmiliarity with advanced surface mountesoldering techniques. If you do not have the proper equitment or knowledge, seek qualified assistance.
Required Parts:
RF PCB:
R157 1,8K to 560 RK73FB2A561J
R160,161 2,2K to 1K RK73FB2A102J
R164 1.5K to 560 RK73FB2A561J
R169 1K to 330 RK73FB2A331J
L76,79 3.3u to 0 R92-0670-05
TX-RX PCB:
R332 2.2K to 6.8K RK73FB2A682J
C340 .022u to .01u CK73GB1C104K
VR1 470 to 3.3K R12-6737-05 (optimal)
Procedure:
- Remove the bottom cover and shields anclosing the RF board and TX-TX board.
- Replace L76 and L79 on the component side of the RF board.
- Replace C340 and R332 on the component side of the TX-RX board.
- Access the bottom side of the RF board and replace R157, 160, 161, 164 and 169.
- Perform S-Meter alignment step 8, on page 95 of the Service Manual. If you cannot obtain "05" of the display, replace VR1 on the TX-RX boardwith the part listed above.
NOTE:
With the exception of C340, this change was incorporated into production from S/N 801XXXXX, C340 was change at S/N 807XXXXX.
Time required to perform this change is 1 hour or less.
Some illustration.
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