TS440 Operation with the MC-85

With some TS-440S transceivers, insufficient modulation may occur when the MC-85 compression switch is turned on. This may be
caused by too much of a voltage drop across resistor R172 on the IF unit of the transceiver . If this is found to be the case, change the
resistor from 1K ohm to 100 ohms.
Required part
100 Ohm, 1/6 Watt resistor (RD14CB2C101J)
PROCEDURE:
1. Disconnect the power supply and antenna from the transceiver.
2. Using a #2 Phillips screw driver, remove the 9 screws from the top cover of the transceiver. Remove the cover and unplug the
speaker wire.
3. Locate resistor R172 on the component side of the IF board (Figure 1).
4. Using a #1 Phillips screw driver, remove the 7 screws that secure the IF unit to the chassis of the transceiver.
5. Pull the board up and rotate it towards the front of the transceiver to expose the foil side of the board.
6. Desolder and remove resistor R172 from the board.
7. Install and solder the 100 ohm resistor in place of R172.
8. Assemble the transceiver by reversing steps 1 - 5.
This modification may be covered under warranty.
Time required for this modification is 0.5 hrs or less.
Image

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Image

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GW1NGL NA7KR Kevin Roberts Ham Radio

Page last updated on 09/10/2012 by Kevin Roberts NA7KR a colection of Ham Radio and Electronic Information