Some TS-950SD owners have reported a transmit image at 18.115 MHz that cause the receiving station to hear distortion on the carrier. If the operating frequency is shift 3 KHz above or below 18.115 MHz, the image disappears. This modification will lower the image level from -30 dB (worse case) to better then - 40 dB by installing a trap on the 455 KHz I.F.
Required parts:
4 pF Trimmer capacitor C05-0308-05
40 pF Trimmer capacitor C05-0309-05
2.2 µH coil L40-2292-14
Modification:
- Disconnect the power cord and antenna.
- Remove the top and bottom covers (18 screws).
- Locate the I.F. board on the bottom of the transceiver. This is the back right board of the 4 boards on the bottom of the transceiver. Figure 1.
- Locate L36 by connector CN17 on the I.F. board. Figure 2.
- Install and solder into place a 4 pF trimmer capacitor across L36. Figure 3.
- Install a 2.2 µH coil and 40 pF trimmer capacitor in series from the output of L36 to ground. The can of L31 can be used for ground. Figure 3.
Alignment:
- Connect the TS-950S/SD to a power meter and 50 ohm load.
- If you are working on the TS-950S digital, connect the DSP cables on the bottom cover to the back panel.
- In the CW mode, adjust the front panel power control for 150 Watt while the ALC level is just at the starting point on the meter. This will create the highest image level condition.
- Using a monitor receiver with narrow filters installed and AGC set to off, tune the receiver to the image frequency.
- Alternately adjust the two trimmer capacitors until the image cannot be heard. This procedure may need to be repeated several times.
- Push the wire harness around the I.F. board toward the chassis of the transceiver.
- Assemble the transceiver.
This modification may be covered under 1 year warranty.
Time required to perform this modification is 1 hour or less.
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