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May 11, 2010

Kenwood TS-940S Mod

TS940s erratic display fix

Intermittent control or display problems that are difficult to correct with the reset procedure may be caused by a faulty ROM socket. The socket should be checked to insure that it makes good electrical contact with each pin of the ROM. If it is found to be intermittent, remove the socket
and solder the ROM directly to the board. It should be noted that units between serial numbers 701XXXX to 811XXXX and from 903XXXX to 909XXXX are not likely to have this failure. In addition, units with a serial number of 909XXXX
and above do not incorporate a socket.


CAUTION

Removing the socket requires good soldering skills. The ROM
is mounted on the Digital A unit and is designated as IC2.
The board, being double sided, has solder connections on
both component and foil sides. When the socket is removed,
it is very important to insure that each pin is completely
solder free. Having to pry up on the socket means that it
is not completely de-soldered and will cause the circuit
foils to tear.

When performing any work on the Digital A board, CMOS
handling techniques must be observed. Such techniques
include using a grounded or isolated soldering tip, avoid
touching the pins of IC chips with your fingers, and ground
yourself with a wrist ground strap.

To remove the socket:


1 Disconnect the power cord and antenna coax.

2 Remove the top and bottom covers from the transceiver.

3 Remove the 2 flat head screws from each side of the
front panel chassis.

4 Loosen the round head screw on each side of the front
panel chassis.

5 Carefully rotate the front panel forward. It will be
necessary to unplug the VS-1 cable from the transceiver.

6 Remove the 4 screws from the speaker mount.

7 Carefully pull up on the mount and rotate it toward the
front panel. Swing the mount toward the right side of
the transceiver and allow it to rest on the Digital B
unit shield.

8 Remove the 8 screws from the Digital A unit shield
plate.

9 Lift the plate and rotate it to the left side of the
transceiver.

10 While avoiding contact with the pins, remove the ROM
(IC2) and set it aside on anti-static foam.

11 Remove the 6 screws that mount the Digital A board.
Rotate the board toward the front panel to expose the
bottom side of the board.

12 Carefully desolder the socket and remove it from the
board. Do not pry up on the socket. If it does not
easily pull off the board, the top foils are still
soldered to the socket.

13 Install the ROM in the board and solder it in place.

14 Assemble the transceiver by reversing steps 1 - 11. Do
not pinch the power switch cables between the front
panel and the body of the transceiver.

Time required for this modification is 1.5 hrs or less.

==================================================================
Note: you might find it easier to break apart the plastic of the
socket and remove the pins one by one. And/Or use a better grade of
socket.
Try just removing and reinserting the Rom in its socket to see
if this fixes the problem before you go to all this trouble. This
might clean a dirty socket contact.    Anyway....
I haven't tried or verified this, proceed at your own risk.
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