TS-430S Repair and Restoration. November 2018
TS-430S transceiver and faults
This is a Kenwood TS-430S
transceiver from the mid-1980s and despite having had several owners in
its life appears in moderately good condition with all knobs and
marking intact. The
radio has in recent times developed various issues in both receive and
of issues requiring attention:
radio is slow to start up and stabilise.
is an unstable tone present in the audio.
has low too very low sensitivity on most of the band pass filter
transmitter has intermittent power output.
S meter is very unresponsive in most receive modes except FM.
VFO is often unstable.
S meter back light failure.
Receiver Sensitivity and Maintenance of the Filter
Unit Board Repair
The receive issues was tackled
first and step one is the measuring the current MDS (Minimum Disenable
Signal) level on all bands to benchmark any improvements. A MDS
measurements of better than -120dBm is a receiver sensitivity figures
that would be expected and a MDS levels of -60dBm is extremely
poor and receiver is effectively deaf. The TS-430S Filter Unit board
switches various band pass filters with relays and the below MDS
results clearly show that groups of frequencies tested correspond with
the various bandpass filter ranges and provides strong evidence that oxidised relay contacts are the likely
major cause of the poor receiver performance.
The Filter Unit (X51-1290-00) was
removed from the radio for detail inspection and relays RL1 to
RL15 contacts were cleaned by wiping the relay contacts with small
slither of gloss paper with contact cleaner. Paper was used to not be
too abrasive on the silver-plated contacts and the paper was gloss to
not leave any paper fibres behind that may interrupt ideal electrical
the plugs and sockets on the Control Unit (X53-1290-000, IF Unit
(X48-1370-00), Control unit (X53-1290-00, RF Unit (X44-1510-11) and
the FM Unit (X48-1340-01) where unplugged cleaned with contact cleaner
and re-plugged, unplugged and re-plugged several times to ensure good
electrical contact. Also, the RL1 relay on the RF Unit (X44-1510-11)
was cleaned as the Filter Unit relays were.
results of eliminating all the poor contacts within the radio were
that the radio recovered full receive sensitivity and the power and
signal strength meter regained meaningful readings. Also, the
transmitter has regained stability.
Unit (X51-1290-00) board layout
Unit (X51-1290-00) board layout
Unit (X51-1290-00) relay section schematic
tone present in the audio during start up.
The receiver suffers from a
strong, unstable and very annoying tone during start-up that
gradually, but not quite disappears over a 5 to 10 minute period. For
approximately the two minutes the tone is around S10 on the signal
strength meter and for most of the 5 to 10 minutes the receiver has
its sensitivity severely degraded.During the initial radio inspection, the IC9
5 volt regulator chip on the IF Unit (X48-1370-00) was too hot to
touch. The IC9 5 volt regulator provides power for the frequency
Display (X54-1630-00) board and by touching around the IC9 regulator
and the wiring to the Display board the annoying tone would changes
amplitude and frequency.
All the electrolytic capacitors
on the Display (X54-1630-00) board have been changed out with some,
but very little change in the tone. The tone now completely disappears
after the 5 10 minute period where as there was often a small
residual tone after this period previously. The replacement of the
electrolytic capacitors is generally a good thing as they are a
potential failure point in older radios.
electrolytic capacitors C118 and C119 on the IF Unit (X48-1370-00)
board have been replaced and the IC9 AN7805 5 volt regulator has
also been replaced with a LM7805CT.
Capacitor Working Voltage
Unit (X48-1370-00) board capacitor replacement.
Fig 4 IF
Unit (X48-1370-00) 5 and 8 volt regulator section schematic
The results of replacing the
above electrolytic capacitors is that the unstable tone present during
start-up has completely disappeared and the radio starts up perfectly
with no sign of instability.Surprisingly
the instability with the VFO has also completely disappeared.
Replacement of the TS-430S meter
backlight with new bright LED
Photo2 TS-430S backlit display
The incandescent meter backlight had failed and
required replacement and while a simple like for like replacement was
possible there was a much superior solution available with bright LED
(Light Emitting Diodes) lamps. LEDs while having many superior
characteristics when compared with traditional incandescent lamps,
particularly when it comes to reliability are not always an ideal
solution. A key performance difference that can make LED not ideal for
display backlighting is that they radiate the light forward in a
narrow beam of between 10 and 20 degrees as compared to the more
omnidirectional pattern of most incandescent globes, therefore if the
backlight as is often the case relies on a more omnidirectional light
the replacement is not as straight forward as simply replacing the
existing incandescent globes with the newer LED light. Fortunately,
the TS-430 radio is well suited to LED back lights for the meter with
the 5mm LED is a good physical fit and the tight angle of the LED is
well suited to the display light guide.
The TS-430 radios dial light is powered by a
13.8V DC supply and it was found that 1.2k ohm 0.25 Watt resistors in
series with the 5mm White, 45000mcd
LED gave a good results and lower running current with the 1.2k ohm
current limiting resistor should provide a very reliably long life for
The 5mm LED snugly fits into the exiting rubber
grommet and can be aimed slightly for best effect.
5mm LED fitted in the exiting rubber grommet and mounting bracket.
Size (mm) 5
Viewing Angle (Degrees) 15
IF Typical (mA) 30
VF Typical (V) 3.2
IV Typical (mcd) 45000
IF Max Continuous (mA) 30
above calculation is for maxim LED performance however in the
fitting of this LED with the TS-430 radio it was determined that a
1.2k ohm 0.25W resistor for this particular LED was sufficient and
will greatly improve the life of the LED and the 0.25W resistor did
not get even slightly warm.
Fully Repaired and RestoredKenwood
of the Kenwood
TS-430S Repair and Restoration