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More Modifications for the Kenwood TS-140
I recently purchased a Kenwood TS-140S after using it on CW for
about a week, I decided to try it on SSB and AM. When I pushed the
AM and SSB mode switches, I heard a constant audio tone emanating
from the rig. As I diconnected the rig, preparing to return it to
the factory, the tone stopped.
Investigating the circuit diagram, I noted that the CW key has to
be unplugged to kill the sidetone. There is no mention of this in
the Instruction Manual.
Perhaps my experience may save others the frustration I
encountered.
Also, amateurs should pay attention to the proper use of receiver
noise blankers. I know of instances where operators were handing
out reports of distorted signals to outhers, only to discover that
it was their improper use of the receiver noise blanker that was
producing the distortion...
Ed, W6XM |
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| TS-140S Intermittent
loss of TX power |
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Author: Trio-Kenwood
Communication, inc.
Service Bulletin no. 928 (11-4-1988)
In some TS-140S transceivers, the drive
transistor, Q2, is not firmly mounted to the heatsink. This can
cause a loss of transmit power after the unit warms up. The
following modification will correct this condition.
- Disconnect the TS-140S from the
antenna and power supply.
- Remove the top and bottom covers. Open
the sub-chassis. Refer to the instruction manual for step by
step instructions.
- Remove the shield plate from the
sub-chassis (12 screws) to expose the filter an final units. Do
not loose the 2 springs that are secured by the right side
screws.
- Resolder Q2 so that the transistor
makes firm contact with the heat sink on the Final unit. Tighten
the transistor's mounting screw. (See the diagram below).
- Assemble the transceiver by reversing
steps 1 through 3.
This modification may be performed under warranty.
Time required for this change is 1/2 hour or less. |
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| Broadcast Sensitivity
Modification for the TS680S / 140S |
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Between .500 and 1.6 MHz attenuation is added to reduce? front-end
overload on the Broadcast band. Some of us BCB DXers find this a
HIGHLY undesirable feature. If I want attenuation I will use the
front panel switch. The following mod will restore the sensitivity
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Cut the land between IC1 pin 11 and R7 (SIGNAL UNIT, M54581P)
Cut the trace between IC1 pin 12 and R10
Add a small signal diode (1N914, 1N4148) between IC1 pin 11 and R7
(Cathode towards R7)
Add a small signal diode between IC1 pin 12 and R7 (Cathode
towards R7)
Trace the lands from pin 11 and 12 of IC1 and you will find a good
place (to the left of connector CN5) to cut these traces as well
as pad to solder the diodes to.
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To enable the TS-140S for transmitting on all bands:
- Disconnect radio from power supply and
antenna
- Remove top and Bottom covers
- Locate the control board (I believe it
is on the bottom --NOT BEHIND TH THE KNOBS LIKE THE 440!!)
- Cut D31 on the control board
- Reassemble the radio
- Reset the radio by holding the A=B
switch while powering up the rig.
Disclaimer: This Modification is for
those who need it to operate MARS only.
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User comment |
Subject: ts-140 mod |
From:
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there
are apparently 2 versions of the ts-140s one of them has a
surface mount chip diode and the other has a normal style
diode . the one with the surface mount you want to be VERY
CAREFUL in removing it you will need to aply equal heat to
both legs of the chip and slide it out of the way DO NOT! LIFT
IT UP it is epoxy on the bottom to the board it will break the
circuit trace and is a pain to repair ...
how ever the other one just cut it off no problem |
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| TS-140S Momentary
transmission when VOX is turned on |
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Author: Trio-Kenwood
Communication, inc.
Service Bulletin no. 929 (11-4-1988)
When the VOX switch is turned on
immediately after the power switch is depressed, the TS-140S may
trip into the transmit mode. This condition can be corrected be
changing the value of chip capacitor C504 on the Signal unit. The
following procedure will detail how to access the capacitor.
Required parts:
C504 0.001µF, 50V chip capacitor
(CK73FB1H102K)
- Disconnect the TS-140S from the
antenna and power supply.
- Remove the top and bottom covers (12
screws). Remove the 4 sub-chassis mounting screws. Swing the
sub-chassis to the left to expose the Signal unit. If required,
refer to the instruction manual for illustrations.
Note: Refer to figure 1 for the
next steps.
- Unplug the wires at connector CN4,
CN12, CN18, CN19, and CN20.
- Remove the nine screws from the signal
unit.
- Slide the Signal unit forward until
the external speaker jack clear the back panel cutout.
- Carefully lift the Signal unit up from
the back side and rotate it toward the front panel to expose the
bottom of the board.
- Locate chic capacitor C504 on the
bottom of the board (see figure 2). If required, refer to the
service manual board diagrams for details.
- Unsolder and remove the C504.
- Install and solder the .001 µF
capacitor in place of C504.
- Assemble the transceiver be reversing
the above steps.
 
This modification may be covered under
warranty.
Time required for this modification is 1 hour or less.
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Author: Bernd DH4MBM
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ufp@neusob.de
I had much problems with my Kenwood
TS140-S and no Circuit Diagram..
The digits of the display began
flickering after about 10 minutes and the display showed nonsense.
The relays of the PA made much noise... After switching the trx
off it worked again .. for ten minutes.
The Kenwood homepages were no help
either...
I opened it carefully, disconnected all
HF connectors and cleaned them with a rubber gum ( I don't know
the exact term, but I mean that thing I drove my teacher mad in
drawing ! ) and it was a little better. After a tip from packet
radio, I removed the EPROM on the Upper platine (circuit board)
and cleaned its legs V E R R Y carefully on the same way. Now the
TS140S works properly since 8 weeks.
73 de Bernd DH4MBM
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Author:
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vegajr@mail.com
While turning radio on press clear and
AM/FM. The display will show all tuning increments.
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User comment |
Subject: 10k resalution |
From: anyham |
note.
that on the ts-140s you don't have to hold the am/fm button
only the clear button "as it states in the manual" |
Mods & tips for the TS-140s, and the one
named "Kenwood TS-140S tip", by Bernd DH4MBM sounded exactly
like what I had encountered. That was when I first got it in
the 1980s. But mine was out of warranty. The guy at Kenwood
told me to remove the CPU socket, and solder the CPU directly to
the board. I suspect Bernd's cleaning contacts was a similar
fix - but may not last forever.
I did that, as Kenwood unofficially instructed me, and that
fixed it. It has lasted for 20+ years since, and no repeat
problem.
(If you post this, please do not post my email address - TNX)
--
Kevin |
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KB2LJJ