Author: Dave, W6NL
Introduction
The Kenwood TS-930, while many years out
of production and lacking many of the technology developments of
the past twenty years, continues to be an excellent HF radio with
a unique ability to hear multiple signals in a pileup. This
particular performance advantage has, for whatever reason, eluded
the designers of more modern radios. As a partner in the new HC8
contest station on Isla San Cristobal, I undertook to obtain and
refurbish a number of 930s, but we were disappointed by the lack
of reliability we experienced.
The problems we observed included
- Several radios experienced outright
power supply failure, and one had a difficult-to-trace low
frequency oscillation in the 28V circuit that involved the
output amplifier, and destroyed amplifier driver bias
transistors (this was cured by replacing the 2N5885 regulator
transistors).
- One radio experienced intermittent
loss of receiver sensitivity, and another experienced loss of
microphone input on SSB.
- AGC overshoot made reception difficult
of signals in the range of S9+20 dB.
I aligned each radio and ran it for a
four-day period at high transmitting duty cycle on CW and SSB,
using computer logging software to transmit into a dummy load
(which itself required a cooling fan). At the end of the burn-in
period I checked for unchanged sensitivity, power output and fan
operation. Despite this we experienced failures in contests, with
the requirement to return the radios to the US for repair.
I was aware of the change of TS-930
design at S/N 310XXXX that responded to the many early problems
(digital board through holes, amplifier through holes, receiver
muting, sidetone, etc.) that are well documented in listings of
modifications, as well as in Kenwood's application notes. Our
radios have serial numbers ranging from 4M to 8M. All have been
standardized to the same configuration, so we would be able to
separate the sources of any problems. All our radios have the
stock CW and SSB IF filters (TS-930 SSB filters are wider than the
pin-compatible ones for TS-940/850) and the PIEXX digital board,
both for reliability, new functions such as main tuning knob
control of RIT when dial is locked, and to be able to use computer
logging and control.
It should be noted that the power
situation at the end of a long rural line is not favorable, nor is
the fact that our radios experience the rough handling as airline
baggage (even in the excellent foam-lined Pelican cases) and then
sit idle for extended periods in the foggy and humid equatorial
mountain-top air. In order to minimize our exposure to line
voltage variations and surges, we configured all the radios for
240V operation and used professional-grade surge protection. The
short line cords are a unique color and are firmly attached to the
radios so other equipment in the shack cannot inadvertently be
connected to 240V through the standard EIA connector. We have the
option to switch to 220V if the line voltage sags, although that
has not been necessary.
With the modifications outlined in this
note, our TS-930s now exhibit excellent reliability, and have
worked well for the entire preparation and contest time in both
modes of the recent CQWW contest. I thought there might be some
interest in what I found was required to make them bulletproof.
Replacing TS-930 Resistors and Shunt
Zeners with Series Regulators
The TS-930 power supply for serial
numbers higher than 310xxxx generates two voltages, 28.5V for the
power amplifier and antenna tuner, and 21.7V for the digital board
and the signal board. The 28.5V is regulated by the two TO3 pass
transistors on the heat sink, and the 21.7V is generated by
separate transformer secondary taps and diodes that generate 31.9V
which is reduced to 21.7V by the TO220 transistor on the power
supply heat sink.
The power switch has a pole that opens
the +28.5V to most of the radio, including the circuit that runs
the 21.7V regulator. This is apparently so the radio will just
turn off without the time delay and rude noises of the filter
capacitors discharging.
The power supply uses high-wattage
resistors and zener diodes in the power supply fan case to reduce
the 21.7V secondary supply voltage 7.5V and 15V for the digital
board (which has 5V and 12V regulators) and for the signal unit,
which has an 18V regulator. The 21.7V is distributed by the yellow
wires via a black terminal block between the antenna tuner and the
filter unit; this block also has the switched +28.5V orange wires.
The original circuit looks like this:
The main schematic diagram of the radio
is wrong, it shows the 33? resistor that is the third supply
voltage for the digital board connected to the 21.7V instead of
the 28.5V line.
The dissipation in the resistors and
diodes is above their ratings, and this could be a reliability
problem. This new circuit replaces the resistors and diodes with
78xx 1 A. TO220 regulators mounted on the power supply heat sink.
In addition to having less dissipation, the regulators are
short-circuit proof. There are holes in the heat sink, and the
TO220 tabs can be bolted with 4-40 small-pattern nuts and bolts. I
use a locking compound on the bolts so they won't vibrate loose
later.
The regulators need capacitors near them,
especially if they are driving the PIEXX board, which has
switching regulators with inductors at the input. The regulators
should be prewired, and the wires are connected to the voltage
points inside the power supply fan case.
To make the change, proceed as follows
(the same steps are necessary to replace the pass transistor with
an NTE377, if the original is burned out).
- Unplug the radio and remove the top
cover.
- Remove the four black screws holding
the fan case onto the heat sink, and unplug the fan wire from
the power supply board so it won't break at the fan connection.
Free the tab from the case bottom, and tip the case down and put
something under it to hold it horizontally to work on.
- Remove the remaining two black screws
holding the power supply heat sink to the radio. You will find
the heat sink will not tip out without additional work.
- Unscrew the screw holding the diode
bridge to the heat sink. This screw will be retained by the
heavy wires from the transformer, so you don't need to pry it
out completely, just free the diode quad from the heat sink so
the heat sink can move.
- Remove the two lugs and heavy red wire
from the TO3 pass transistors by unscrewing the two middle
screws while holding the nuts with long-nose pliers on the
inside. Leave the screws in place in the transistors to hold the
insulating washers.
- Now you can tip the heat sink forward
far enough to be able to reach the screw that holds the pass
transistor. This transistor has had loose screws in some radios,
so tighten it up while you can. If you unplug the pass
transistor, be sure to note which way the plug goes on (some
have plugs, some have the blue, green and violet leads soldered
on and covered with heat shrink tube).
- Locate the field of small holes near
the upper edge of the heat sink, near the outside edge of the
radio. As viewed from inside the radio, the two regulators mount
to the holes in the bottom row (the top row is also OK, and
easier to reach if you are not removing the heat sink). Before
you do anything else, route the wires from the regulators
beneath the heat sink so they can be connected to the terminal
strips in the fan case.
- The 4-40 small pattern nut just fits
between the heat sink fins. Use a thin tool that can hold the
nut on the end, and orient the flats of the nut to go between
the fins. It's helpful if the parts are magnetic, so you can
recover a dropped nut (be sure to cover the holes in the chassis
with tissue or a rag). Use a 4-40x3/8" screw to fasten the
regulators to the heat sink. The same nuts and screws are used
in DB9 and DB25 connector shells. I use some heat sink compound
on the back of the regulators. No insulation is required. Check
again to be sure the screw for the TO220 pass transistor is
tight and the transistor is oriented up so you can get to the
terminals.
- Reconnect the lugs to the backs of the
TO3 pass transistors, holding the nuts with log-nose pliers and
using a drop of retaining glue or Loctite. Reattach the diode
quad to the heat sink.
- Attach the heat sink to the radio with
the middle black screws. Check that there are no wires being
pinched between the heat sink and the chassis. Now you can hook
up the regulator wires to the terminal strips in the fan case.
- The resistors to be replaced are
inside the power supply fan case. You will notice that the
resistors will have lost their color coding from overheating,
and the terminal strips may be somewhat charred, from
overheating. Cut out the two 82? resistors and their zener
diode, and cut out the 22? resistor and its two zener diodes.
You can save these in case of trouble, but the new circuit
should be more reliable.
The fan case should now look like this:
Cut to length and solder the Yellow,
Black, Gray and White wires to the terminal strips, making sure
they are connected to the same color wire that is already there.
Dress the wires in place to avoid the fan with a tiny
nonmetallic cable tie or twister.
- Plug in the radio, being careful of
high voltages at the power switch and transformer. Connect a
digital voltmeter to radio chassis ground and check the voltages
at the terminals in the fan case. Turn the radio power on
momentarily to check each of the voltages:
Orange +28.5
Yellow +21.7
White +15
Gray +8
- Unplug the radio. If you wish, you can
replace the 100ohm resistor with a 5W unit, and the 33ohm
resistor with a 3W unit. Using a piece of wire or an oiler,
place a drop of oil on the fan shaft. Check to be sure the fan
wires aren't broken, and reattach the fan case with the four
black screws. Plug the fan back into the power supply board.
Replace the top cover and test the radio.
Replacing the 21.7V Pass Transistor
Despite the attention in the literature
to the 28.5V TO3 regulators that supply the power amplifier,
almost all of our power supply failures have been traced to the
21.7V regulator circuit. As the pass transistor is failing the
radio will typically exhibit unusual operation, such as chirpy
signal or intermittent display.
The 21.7V regulator is a pair of cascaded
emitter followers driven by a 22.5V zener diode fed from the 28.5V
supply switched through the power switch. The zener diode D10 and
the first transistor Q6 are on the power supply board, and the
second transistor Q3 is the TO220 transistor on the heat sink. The
schematic incorrectly shows C13 to be 25 uF 100V (it is 100 uF
25V).
Use an insulated clip probe. If the
output of the 21.7V supply measures OK on the yellow wire at the
terminal strips in the power supply fan case or the black terminal
strip in the narrow space between the output low-pass filter and
the antenna tuner, then all is OK.
If the voltage is not correct, it will
typically be either 31.9V or near 0V (say, 0.5V). This means the
pass transistor Q3 is either shorted or open.
- Unplug the radio and remove the top
cover.
- Plug in the radio and power on,
measure the voltage on the orange wire, either at the top of the
power supply board or at the 33ohm resistor in the power supply
fan case. It should read 28.5V. If it is OK, the 28V regulator
on the board and the pass transistors are OK.
- Measure the voltage on the yellow
wire, either at the power supply fan case terminal strips (you
can reach them with an insulated probe in the slot above the
heat sink) or at the black terminal strip in the space between
the output low-pass filter and the antenna tuner. If it is
approximately 21.7V, Q3 and Q6/D10 are OK and the problem, if
any, is not in this part of the power supply.
- If it is not 21.7V, it will typically
be either approximately zero volts (0.5V or so) or 31.9V. This
means Q3 either has an open or it has a collector-emitter short
. Usually, but not always, if Q3 is zapped it will take Q6 and
D10 with it. If the voltage isn't right, you need to determine
if the problem is Q3 or Q6 or both. With the radio unplugged,
unplug the 5-pin connector on the power supply board and use a
digital voltmeter with a diode scale to check the Q3 B-C and B-E
diodes; also check for a C-E short. Poke a short length of
solder into the connector, and use clip-type meter leads. The
readings will typically be (assuming the open circuit meter
reads 1.4V)
Pins on Red lead Black lead
5-pin conn. on Base on Base
Grn-Blu 2-3 0.7 1.4
Grn-Vio 2-5 0.7 1.4
Blu-Vio 3-5 1.4 1.4
- If the readings are OK, it is likely
that the problem is on the power supply board. If any of these
readings is not as expected, Q3 is dead and will have to be
replaced (a remote possibility in the case of an open circuited
diode is a bad connection at Q3, so check the connector by
wiggling it). If Q3 has blown, it may also have taken Q6 and D10
with it. It is worth disconnecting Q3 before removing anything
and checking Q6 and D10 to determine if you also need to take
out the power supply board. Either unplug the connector at Q3 or
cut the three thin wires right at Q3. Be careful not to short
anything when measuring voltages, as you will hate yourself if
you zap a working circuit while measuring voltages. Reattach the
5-pin connector to the power supply board, plug in the radio and
turn it on momentarily to check the voltages on the three wires:
Vio 31.9
Grn 22.3
Blu 0 (with Q3 disconnected, 21.7 in working regulator with Q3 connected)
- If these voltages are OK, the PS board
is OK; unplug the radio and review the data
| 21.7V OK |
Q3 OK |
This
part of PS is working; check resistors in PS fan case, look
for pinched white or gray wires, check 7818 18V regulator on
Signal Unit |
| 21.7V
bad |
Q3 OK |
Probably
means Q6/D10 bad; remove power supply board and replace |
| 21.7V
bad, 22.3V (Q6) OK |
Q3 open
or short |
Replace
Q3; Q6/D10 OK |
| 21.7V
bad, 22.3V (Q6) bad |
Q3 open
or short |
Replace
Q3 and Q6/D10 |
Replacing Q3
- To replace Q3, you need to remove the
power supply heat sink as in steps 1-6 above. Remove the four
black screws holding the fan case onto the heat sink, and unplug
the fan wire from the power supply board so it won't break at
the fan connection. Free the tab from the case bottom, and tip
the case down and put something under it to hold it horizontally
to work on. Remove the remaining two black screws holding the
power supply heat sink to the radio. You will find the heat sink
will not tip out without additional work. Proceed to free the
diode quad and the lugs on the TO3 transistors so you can get at
the screw that holds Q3.
- Now you can tip the heat sink forward
far enough to be able to reach the screw that holds the pass
transistor. If you unplug the pass transistor, be sure to note
which way the plug goes on (some have plugs, some have the blue,
green and violet leads soldered on and covered with heat shrink
tubing, my preference). Remove the pass transistor and replace
it with a new one. If the transistor has a gray silicone
insulator under it, use it again with the plastic washer to
insulate the screw; if it has a mica insulator, use a new one
and smear a bit of heat sink compound on both sides before
placing it. If there is a connector, plug it onto the transistor
now; if you need to solder the wires on, cut the pins on the
transistor shorter and use heat shrink tubing on the wires. In
some radios, I've found this screw was not tight so be sure it
is snug when you are finished so the transistor won't overheat
and fail.
If you are going to replace the
resistors with regulators, now is the time to do it while the
heat sink is accessible. Also, if Q6/D10 are to be replaced,
it's easier to do with the heat sink out of the way.
- Reconnect the lugs to the backs of the
TO3 pass transistors, holding the nuts with long-nose pliers and
using a drop of retaining glue or Loctite. Reattach the diode
quad to the heat sink.
- Attach the heat sink to the radio with
the middle black screws. Check that there are no wires being
pinched between the heat sink and the chassis. Clean, oil and
replace the fan.
Replacing Q6 and D10
- You can check Q6 for a
collector-emitter short by measuring from pins 1-4 of the 5-pin
connector (should show an open with both polarities), but you
can't measure all the junctions. If you need to replace Q6 or
D10, you will need to remove the power supply board. Make a
sketch of where all the connectors and wires go. If both Q3 and
Q6 are blown and you have the heat sink open, do the power
supply board repair before reinstalling the heat sink. The power
supply board can be removed without removing the heat sink, but
it is more convenient to do it before you reinstall the heat
sink if you have replaced Q3.
Unplug the inline bayonet connector in
the red wire to the power amplifier. Unsolder the heavy yellow
and white wires from terminal 28A. Unsolder the orange wires
from 28B. Unsolder the black ground wires from the ground
terminal. These terminals are at the top of the power supply
board. Wear safety glasses so you don't flick solder in your
eye, and use a solder suction pump to remove excess solder.
Typically, the lugs will come unsoldered from the circuit board,
but it is easy to put them back straight after the wires are
unsoldered.
- Unplug all the connectors, noting
which goes where. Now remove the two screws that hold the
bracket to the chassis, using a magnet (a necessary tool for any
of these jobs) to reclaim them so they don't roll down a hole
into the space under the signal board (it's a big job to remove
and replace it). Lift out the power supply board.
- Remove the power supply board from the
bracket by removing the four screws at the corners. Now you can
locate Q6 and D10. Once you have gone this far, you might as
well replace both, since it takes a separate setup to measure
the zener, and the transistor is easy enough to change out. Use
a solder suction pump and observe the polarity of the zener and
the connections of the proper leads. After the old transistor is
removed, you can check the junctions using the digital
multimeter. I'd add a 47 ohm current-limiting resistor in series
with the collector of Q6.
- Replace the power supply board by
reattaching it to the bracket, then reattaching the bracket to
the chassis. Be careful not to pinch under the bracket any of
the wires coming from the fan case or the back of the chassis.
Plug in all the connectors. Resolder the black wires to the
ground terminal, the orange wires to the 28B lug and the yellow
and white wires to the 28A lug. Make sure the lugs are
well-soldered to the circuit traces. Plug in the red wire to the
power amplifier.
- Before you power up, check with an
ohm-meter from the orange (28.5V) and yellow wires (21.7V) to be
sure there are no shorts. You should see capacitors charging up
in either case. If there is a short, check carefully for a
pinched wire under the power supply board. If this measurement
shows no shorts, plug in the radio and power on, measuring the
voltages on the orange and yellow wires (you can reach the
yellow wire terminal in the fan case with a well-insulated
probe). The voltages should be
Orange 28.5
Yellow 21.7
If OK, you are done and can replace the
heat sink, fan cover and case top. The 21.7 voltage has no
effect on any critical adjustments, so no realignment is
required.
Fan Operation Check or Repair
Check the operation of the 12V Power
Supply fan and the 12V Power Amplifier fan by running into antenna
or dummy load at 50W as follows:
Mode: TUNE
Send/Rec: SEND
Car: Midscale on meter
Power: 50W
After a few moments both fans should
start up. In any event, proceed to refurbish as follows:
- Unplug radio
- Remove 4 black screws holding metal
tabs top and bottom of fan box.
- Tip PS fan assembly back, rotating
around wires at bottom (pull some slack in the black fan wire
from radio so the weight of the fan motor won't break the
connection to the fan))
- Fan blades should spin freely when
turned by hand, with the lumpy feeling of a DC motor
- Check for mechanical interference with
fan blades, for example by fan screen; correct if found
- Fan white wire should read about 60?
to ground, and black wire should connect to ground; if motor
reads open the fan is doomed and will need to be replaced
- Remove 4 silver screws on outside of
fan box to remove fan motor assembly
- While fan is out, remove screen and
reshape it to bow out enough to ensure clearance
- Place a drop of WD-40 or light oil on
the bronze bearing where the shaft goes through, spin shaft
- Check for mechanical interference; on
later serial number radios there is a small flat spring wiping
the motor shaft under the fan hub to quiet the motor, don't
damage it
- Being careful not to crush any wires,
replace the four silver screws to fasten fan to box; make sure
no wires rub the fan blades; look in holes and rotate the screen
to get openings for the four screws
- Test fan by plugging in radio, run 50W
transmit test with antenna or dummy load; fan should start and
run quietly if motor measured good. Voltage on fan should be 10
to 12 VDC when PS is hot
- Some have suggested wiring the fan to
run continuously through a diode from the +8V available in the
fan case, but this has not proven necessary with the power
supply modification to remove the shunt regulators, as the heat
sink runs noticeably cooler after the mod
Once PS fan is working, clean and oil the
Power Amp fan, which comes straight out after four mounting screws
and washers are removed.
If a either fan is beyond repair,
substitute a replacement or an 80x25mm 12V computer muffin fan.
New holes are needed for the mounting screws, which are 2.81" on
centers (the existing holes are 2.45" on centers). Wire the red
fan wire to the white supply wire, and the black fan wire to the
black supply wire.
Lubricating the Top Cover Door
The sliding door in the top cover becomes
very difficult to move after some years of service. Any time you
have removed the top cover, lubricate the sliding door in the top
with Silicone liquid or grease lubricant on the plastic slides.
Press down one edge, hold in place with screwdriver, wet the
corner of piece of paper with Silicone spray, run it between the
door and the lid, do same all around and also between black
plastic and door. This is much easier to do while the cover is
off. Be careful of the line voltage on the POWER switch on the
front panel, and don't short anything around the power supply
voltage regulator. Do not use a petroleum-based lubricant such as
WD-40 on plastic parts, as they will swell and deteriorate.
Line Voltage Change to 240V
Because of low line voltage and neutral
wire problems, our 120V line voltage ranged from 106 to 113V,
causing hum when the regulators dropped out of regulation.
Attempts to rewire the transformer for 100V operation with low
line voltage (below 110V with load) resulted in overheating of the
power supply, since with such a large change (20%) the unregulated
voltages rise above the design limits.
If the 120V line voltage is low, use the
240 or 220 volt switch position.
- Replace the 6A fuse with a 4A fuse;
retain the 6A fuse if it is desired to change back later
- Turn the switch on the bottom of the
radio to 240V, or 220V if the voltage is low
- Plug in special yellow 240V line cord,
attach to rear panel so it won't be used on a 120V radio
- Plug into a 240V outlet or extension
cord (surge absorber preferred, make sure ground is OK)
Cleaning Signal Unit Connectors with
Contact Cleaner
On several occasions receivers have
suddenly lost sensitivity for extended periods, and other radios
have had sudden complete interruptions of microphone input. While
there can be other causes for these intermittent failures, they
were in each case traced to the connectors at the Signal Unit. In
all cases the intermittent behavior was eliminated by cleaning the
contacts of the connectors in the particular signal path.
The idea developed that this reliability
issue was due to corrosion of the connectors on the Signal Unit.
It was decided to clean all of the connectors to avoid any
recurrence of the intermittent problems, a course which has been
successful. In some cases it was possible to observe discoloration
of the connectors that was possibly indicative of corrosion.
I remove each and every connector, one by
one, and spray or dab the pins with contact cleaner, then rub the
connector in and out a couple of times. I do all the connectors,
including the filter connectors and especially the microphone and
coaxial RF connectors. This has solved several complaints of
intermittent or deaf radio or no transmit audio on SSB. The
intermittent problems went away.
After I did this, I learned from several
other TS-930 users that they had experienced the same problems,
and had resolved them in essentially the same way.
AGC Modification with Germanium Diode
An AGC modification results in a big
improvement in the ability to copy signals in the S9 to S9+20
range. This modification prevents the AGC overshoot that blanks
the first character of a loud CW signal, with no bad side effects.
A germanium is diode placed across D125 under the CW 455 kHz
filter, with the "bar" end toward the rear of the radio (opposite
to the bar on D125). The new diode is soldered across D125, which
is located under the large 455 kHz 500 Hz IF filter.
- Unplug radio
- Turn radio upside down and remove
bottom cover (8 screws, including the ones that hold the top
cover at the sides).
- Locate the 500 Hz 455 kHz crystal
filter (the largest one, on your right as you face the bottom of
the radio from the panel end), lift out harness, remove screw at
each end and lift it out.
- Underneath you will see R375 and D125;
solder the Germanium diode across D125 as shown.
- Replace IF filter, being careful not
to damage connectors; push the connectors down tight before you
replace the screws. Put a label "R375+1N270" on the filter to
show the AGC mod.
- Test the radio before you replace the
bottom cover; watch out for line voltage at the back and behind
the POWER switch on the panel.
- Before you replace the bottom cover,
you should also clean the connectors on the Signal Unit.
Alignment with Non-contacting Pickup
for Oscillator Frequencies
In some cases it is desired to check or
adjust the transceiver alignment while not having access to formal
test instruments, and without opening the radio and exposing the
circuits to possible damage through connecting test leads. Use an
insulated wire as a pickup antenna by pushing an insulated loop
through the appropriate tuning hole in the bottom (or side cover
in the case of the 20 MHz master reference oscillator). A second
radio can be used to measure the frequency to the accuracy
required.
The first step should be to check the
accuracy of the reference oscillator. I connected a small outdoor
antenna wire to an insulated loop pushed into the side cover
opening for the oscillator adjustment, with the other end of the
loop connected to the antenna connector on the radio. With this
setup, monitor the 20 MHz signal of WWV and adjust the insertion
of the loop for somewhat equal signals from the external standard
and the signal from the internal oscillator. You will be able to
hear the beat note and adjust the oscillator for zero offset from
the standard frequency. Let the radio warm up for 30 minutes or so
to be sure everything has stabilized.
As another example, consider the
alignment of the Carrier-2 oscillator used to provide variable
bandwidth. The variable bandwidth tuning (VBT) uses two IF
filters, one at 8830 kHz and the other at 455 kHz. The conversion
oscillator at 8375 kHz determines the degree of overlap of the
filter passbands. If the VBT knobs are set to widest position, the
conversion oscillator should be at exactly 8375.0 kHz.
The can be done by connecting a counter
(for example, an antenna impedance bridge counter) through a
DC-isolated probe to C298 of the signal board, but if there's no
other work to be done leave the case closed and use an insulated
wire loop poked into the hole as an antenna to hear the oscillator
on a second radio.
 
The radio should be set up (see Service
Manual, pg. 67, adjustment and test points are on pg. 77)
Mode: USB
Transmit: REC
VBT: CW, High Cut fully CW, Low Cut fully CCW (no narrowing)
- Measure the frequency at 8375 kHz
- Adjust VR23 so there is no change in
frequency from transmit to receive
- Adjust TC3, the small trimmer
capacitor, so the frequency is exactly 8375.0 kHz
At this time you should also check the
carrier oscillator at 8830 kHz
The radio should be set up (see Service
Manual, pg. 66, adjustment and test points are on pg. 77)
Mode: USB
Transmit: REC
VBT: CW, High fully CW, Low fully CCW
- Measure the oscillator frequency,
which should be 8831.5 kHz.
- Adjust VR27 so there is no change in
frequency from transmit to receive
- Set TC4 so the frequency is 8831.5 (I
prefer 8831.6, you can go by the sound of the receiver audio to
get the upper and lower signal levels equal, at +300 and +2.9
kHz.
Now switch to LSB, and set TC5 for 8828.5
kHz. Switch back and forth between USB and LSB, and trim the LSB
oscillator until the noise sounds the same. Then switch to CW and
NARROW, set TC6 for 8830.0 kHz. Last, connect a dummy load or
antenna and switch to FSK transmit and set VR26 for 8827.79 kHz.
Last, check the setting of the CW Pitch
and the Notch. Turn on the Marker oscillator, put the rig in CW
mode, and check to see that the pitch covers the desired range. I
set the CW Pitch so it is zero beat with the knob at 12 O'clock,
so you can tune either sideband. The CW Pitch is set by L173 at
the far right rear of the Signal Unit (bottom of rig). While you
have a received tone, check the Notch by pushing in the NOTCH
button and tuning the control for a null. With the offset tone at
1.5 kHz, the null should be at 12 O'clock. If it's not close,
adjust L167 on the Signal Unit.
Don't forget to set Moni, Sidetone and
other adjustments (AGC Delay, for example) before the radio is
stuck under a shelf or cabled in place.
A Note on Alignment Levels
Clif Holland of Avvid, a respected
repairer of Kenwood radios, emailed me to note that the Japanese
specification for the standard signal generator used in alignment
is different from the US signal generator calibration. The 930
service manual refers to signal levels in dBuV, so I had assumed
0dBuV was 1 uV and 40dBuV was 100uV.
But not so. Clif is right and I'm off by
6 dB. I checked it out, and although I see no mention of the issue
in the TS-930 or TS-950 manuals, I found a table in the TS-850
service manual, pg. 96, that confirms this. It has two columns:
Japanese "SG" American "SG"
-6dB 0.25uV
0dB 0.5uV
6dB 1uV... etc.
40dB 50uV... etc.
Apparently the JA generator defines
output in terms of open circuit voltage rather than voltage into a
matched load. This 6 dB difference affects the alignment of the RF
PIN attenuator start point as well as the S-meter settings for S1
and S9. Since the manual specs are ±4 dB anyway the difference
will be mighty small except for a more active S-meter.
CW Reception on USB
To listen on USB on a 930 in CW mode,
adjust the "CW Pitch" (BFO) coil L-173 (yellow core, farthest
right-rear on bottom, there's a hole) so you have zero-beat at
center position (12 o'clock) on the CW PITCH control on the front
panel. If measuring frequency of this oscillator, this yields
100.0 kHz rather than 99.2 kHz.
Now if you turn the pitch control
clockwise from center you get LSB as before, but if you turn the
pitch control CCW from center you get USB. No retuning of filters
or carrier oscillators is required. This mod has no effect on SSB.
I use this on our TS-930s at HC8. The
only problems are that it makes the TUNE mode zero-beat if the
pitch knob is centered, and also if an op isn't familiar with the
setup on CW it can be concluded that the receiver is not working
if the pitch knob is centered.
Operating Notes
I found it's difficult to tighten the nut
on the Antenna UHF connector. Lacking a special spanner, you can
carefully tap the Antenna connector nut with screwdriver and small
hammer, as with the nuts in electric boxes. Don't overdo it.
For use with an external receiving
antenna, one needs the hard-to-find 262 degree 8-pin "horseshoe"
DIN-8 connector used to bring a separate receiving antenna in and
out of the transverter socket (available from Kenwood and Yaesu,
and HRO, but seldom found when needed). In an emergency we found
that a standard DIN-5 connector will plug in and provide access to
the receiver input and ground, while the small slide switch makes
the transmit antenna output available at the adjacent RCA phono
connector to connect to an receive-antenna selector switch
(inadvertent mis-setting of this switch is a source of occasional
complaints of deaf receiver).
It's good practice to have a relay that
disconnects the receiver input from any antenna and shorts it to
ground during transmit, so the transmit power isn't returned to
the receiver from a separate receiving antenna. When used as a
second receiver in a multi-op setup, this relay can also be run by
the AMP relay line of the transmitter on the same band.
We don't use the noisy and slow amplifier
relay (28V to NC pin), but make a transistor switch adapter in the
DIN-7 plug for the PTT input and AMP output. This is faster, less
noisy and more reliable. With the AL-1200s we use the speedup
circuit found on K6XX's web site.
Naturally, we've had to cure hum and RF
problems when using two radios and a microphone switch box along
with a voice recorder, but this has been resolved by using double
shielded twisted pair but not connecting the shields at both ends
except through RF bypass capacitors. I have a circuit, based on
K8CC's in the NA manual, that works very well for me. There are
some curious audio/brain effects I've read about in a Bell Labs
book on hearing and sound that are interesting to experiment with,
including wiring headphones for out-of-phase reception.
One remaining problem is RF leakage of
the display waveforms on the band-select cable from the PIEXX
board. It appears this should be shielded. With the removal of the
resistors in the PS fan case there is now room for some real
back-panel connectors, DB9(F) for the RS-232 connection and
DB25(F) for the band data. I cut off the unneeded wires in the
RJ45 connector to avoid any problem with the PIEXX board.
References
There are a number of sources of two text
files listing mods and fixes for the early TS-930.
http://www.qrz.com/download/mods-t-z/ts930.txt
is an updated version of a posting by WA2ISE called "TS930 repair
notes (long)." There are many other sources of this document, to
be found with any search engine under "ts-930 mods" or the like.
The newest version notes that replacement dial light bulbs should
be 28v @ 40mA, not 12V, and that the part number for these bulbs
is not correct in the service manual, and should be B30 0826 05.
http://www.artofhacking.com/Tucops/Radio/two_way/TS930.TXT
is one source of a different document that is "a list of favorite
changes that can be made to the Kenwood 930."
http://www.kkn.net/~k5tr/ts930fix/ts930doc.pdf
is the source of a definitive service bulletin from TRIO-KENWOOD
GMBH about "Digital Unit through-plated hole defects and their
symptoms." The PDF was created by K5TR from a MS word doc from
NØSS.
http://www.qth.net/archive/kenwood/,
the Kenwood mailing list archive, is a great source of
information, but is not indexed by subject.
I haven't been able to find a good
reference for the idea of replacing R400 of the Signal Unit with a
7912 TO220 regulator (mounted on the heat sink at the back of the
Signal Unit). If I were to do this, I'd clip one lead of the 12V
zener diode D210.
Using the current-limit feature of the
723 regulator chip, some have built a protective crowbar circuit
to keep the 28.5V from damaging the amplifier transistors by
running away if the regulators fail. It is the same as the 28V
supply circuit in the 1988 ARRL Handbook, and I haven't felt it
necessary (yet). ZL2DX emailed me a copy of a 1992 circuit by NJ6O
from the Kenwood/IRCI newsletter, now be available through W2VJN
at
http://www.qth.com/inrad/pubs.htm.
Replacement Semiconductors
Although there are many sources of the
original transistors, it has proven convenient and reliable to use
the current replacement semiconductors offered in the US by NTE.
Here is a list of suitable replacements:
2SD843(Y) NTE377
2SC2235(O) NTE382
XZ-225 NTE5080A
2N5885 NTE181
MRF485 (2) NTE236 (2)
2SC496(Y) NTE295
2SB861(C) NTE398
2SC1815(Y) NTE85
I've looked in vain for a TO220 power
transistor that does not require the insulated mounting, but have
not found one that has low enough thermal impedance and high
enough current and power ratings. I've seen a suggestion to
replace the 22V emitter follower with a 7824, but this might
sacrifice the control by the switched 28.5V. I select from the
NTE5058A (nominally 22V) individual zeners that provide 22.5
volts; the lead length of mounting to the circuit board affects
the voltage, which rises with the operating temperature of the
diode. If I measure them in free air with clip leads, I get a
higher voltage reading because they get a lot hotter after a
moment's operation.
I was surprised to be able to make a
successful replacement of the expensive but burned out MRF485 RF
driver transistors (don't ask!) with the relatively inexpensive
NTE236. I made no effort to match the NTE replacements, and the
amplifier seems to work fine; I reset the bias adjustment per the
instructions in the service manual.
I was concerned about the thermal
impedance of the replacement TO3 transistors NTE181, which also
have relatively low current gain, but a matched pair (NTE offers
these designated as NTE181MP) was used with success to replace a
pair of defunct 2N5885 28.5V regulators.
Kenwood Service Bulletin Reference
TS-930S ASB-0863 INCORRECT LINE VOLTAGE SETTING
TS-930S ASB-0866 CW HETERODYNE TONE WITH VBT CONTROL
TS-930S ASB-0867 SSB TX AUDIO TONE QUALITY SN < 3080001
TS-930S ASB-0868 LOSS OF RX SENSITIVITY
TS-930S ASB-0869 PLL UNLOCK / BLANK DISPLAY
TS-930S ASB-0872 CW PITCH TONE SHIFT WHEN MONI SWITCH IS ON
TS-930S ASB-0873 CW VBT - SIMPLIFIED ALIGNMENT
TS-930S ASB-0874 RF FEEDBACK WHEN USING EXTERNAL SPEAKER
TS-930S ASB-0875 RX AUDIO OSCILLATION
TS-930S ASB-0876 RF FEEDBACK INTO MIC CIRCUIT
TS-930S ASB-0879 ALC LEVEL DRIFT AT 28 MHZ
TS-930S ASB-0881 POWER SUPPLY SURGE PROTECTION
TS-930S ASB-0884 15 MTR INTERNAL BEAT NOTE
TS-930S ASB-0886 INTERMITTENT TX POWER OUTPUT
TS-930S ASB-0893 NOISY POWER SUPPLY FAN
ftp://216.98.255.24/Amateur/AmateurServiceBulletins/
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KB2LJJ
