Kenwood Ts-440s Internal Antenna Tuner Repair?

Kenwood TS-440S (TS 440 S TS440S) Circuit Improvements

Problem: Limited transmit frequency coverage.
Ready: Cutting D80 on the Command Unit for 1.6MHz to 30MHz transmit adequacy. D80 is about 2" from D66, which is cutting for 10Hz frequency readout.

Problem: Lack of crispness in the RX sound, which makes the sibilant parts of man speech difficult to distinguish from each other. This is acquired by a �p;5db roll-off at 3000Hz in the RX audio.
Fix: Change C51 [0.033�F] on the IF Unit, well-nigh L5, to .005�F [5000pF/5nF]. This will reduce the curlicue-off to a more adequate �p;i.4db at 3000Hz. "After modification, the RF Gain command should be backed off [CCW] until the band/sky-noise decreases to a comfy listening level. This volition not interfere with the reception of moderately weak signals.

Problem: Even while listening on a large, external speaker, music sounds flat and tinny because the sound frequency response rolls off beneath 200Hz.
Fix: There are a number of capacitors in the RX audio amplifier circuits that tin can be increased in capacitance to restore the depression-end audio. These capacitors are in the IF Unit. They are: C60, C66. C67, C69, C170 and C175. The increase in capacitance should be 4 times. {Annotation: Some capacitors in the audio circuitry can non exist arbitrarily increased in value without causing unacceptable tradeoffs.} C175 can exist replaced with a 1000�F, 10V unit, whose full-length leads are sheathed in Teflon sleeving, except for the last 8mm, to permit soldering to the PC board. This is done because the board-space allotment for the stock C175 is too small for the larger, replacement unit. The new capacitor is folded over and tucked in appropriately.

Problem: Tinny/sparse-sounding transmit audio.
Gear up On the IF Unit of measurement, change C135 {0.1�F}, near the center-board fastening screw, to 0.47�F.

Problem: The stock, muRata CFJ455K14 SSB filter in the 455KHz IF has a selectivity shape-cistron of 2 to i. This is definitely less than wonderful. The stock SSB filter in the TS-830S and TS-940S has well-nigh the same bandwidth at minus 50db, just it has a much improve shape factor and information technology is mechanically and electrically interchangeable with the stock filter in the TS-440S. The better filter is a muRata CFJ455K12 or CFJ455V12, which volition noticeably ameliorate the transmit and receive, SSB audio quality of the TS-440S. This filter is bachelor from Trio-Kenwood as p/north: L72-0333-05 for $42.89 {December 1989}. If you want SSB double-filtering in the 440'due south RX, the TS-940S' matching, viii.83MHz, YK-88-S1, 2.7kHz SSB filter is bachelor from Trio-Kenwood as p/n L71-0222-05]. for $66.62 {December 1989}. This filter goes in the optional SSB filter infinite on the IF Unit. For listening to an uncastrated-male vocalism, the YK-88-S1 volition produce better-sounding, and more understandable, audio than the Kenwood-recommended optional YK-88-Due south, 2.4kHz filter. A pair of TS-940 SSB filters volition give the 440 the same superb selectivity that comes with the 940.

Alignment: Supply a signal to the receiver. Set the TS-440S' selectivity switch to M2, the unmarried filter position. The USB and LSB carrier oscillators [DIP switches on Command Unit] should be reset so that there is roughly 20db of RX, SSB carrier-suppression for each sideband at zerobeat. [use the 440'due south 20db ATTN equally a standard] {Use 15db rolloff at null-beat for more low-end audio, or 25db roll-off for more high-cease audio and/or better unwanted sideband suppression} This completes the alignment of the carrier oscillators. >>> If you installed BOTH filters: on LSB tune the 440 above the calibrator's zerobeat frequency and note the 20db (or the whorl-off db yous used to a higher place) roll-off point. This should be around iii.1KHz, �200Hz higher than zerobeat. Put this frequency & LSB into VFO B. Put the zerobeat frequency & LSB into VFO A. With the Selectivity switch set to M1 [double SSB filter], the 8.375MHz oscillator on the IF Unit is adjusted [TC2, in the lower left corner of the PC board] so that the improved skirt selectivity on the double filter position is as distributed betwixt the zerobeat 20db rolloff point [VFO A] and the high-frequency 20db rolloff indicate [VFO B]. The comparison can be done by watching the S meter and repeatedly pushing the A/B push on the 440. [use fast AGC to reduce settling time] Note 1: TC2 is installed backwards on the PC board and so that the rotor adjustment slot on TC2 is hot instead of grounded. This causes the capacitance of TC2 to alter when a metallic screwdriver is used to make the adjustment.

To fix this problem, TC2 is removed, reversed 180 degrees and re-soldered on the PC lath. Note 2: see IF Unit schematic, CF2, the AM filter. At that place is a 1K Ohm resistor [R49] in series with the input [D13] to the filter. This resistor provides a closer impedance match betwixt the 2000 Ohm filter and the source [L4]. A like resistor can exist installed in series with D12 at the input to CF1.

Problem: RX audio distortion. {This problem seems to be more than prevalent in early product radios. At that place may take been a recent factory component change to reduce receive distortion.} There is one designed-in source of distortion and several other possible sources of distortion. The designed-in source of baloney exists because not enough forward bias current is applied to the switch diodes that select the SSB [D23] , AM [D24] , and FM [D25] audio detectors. Here'southward why: A mixer is a nonlinear device. Nonlinearity and baloney get paw in hand. Diodes make good mixers when their forward current is in the range of 0.05mA to well-nigh 0.6mA. At currents above i.5mA, diodes are reasonably linear and they make good switches. The switch diodes in the TS-440S accept enabling currents of from 0.2mA for FM to 0.28mA for SSB, so the switch diodes are operating in the region of maximum nonlinearity, which results in distortion. The ready is simple: Increase the forrard bias DC-current through the diodes to roughly 2mA. This is accomplished by decreasing the resistance of each DC-bias resistor to about 1k Ohm. When these resistors are decreased in value, the 5000 Ohm impedance of the depression-level audio circuits decreases to about 500 Ohms and the values of the coupling capacitors must be increased accordingly to foreclose a rolloff of the low frequencies. Similarly, the resistors that are in series with the audio signals in these circuits must exist decreased in value to showtime signal attenuation. The capacitance of the filter capacitors between switch diode bias resistors (for SSB: C52, 4.7�F) must be increased to compensate for the decreased value of the bias resistors.
Fix for SSB audio detector and D23 switch: In the left, rear corner of the IF Unit, alter: R71, R73, R74, and R85 to 1k Ohm; C53 to 47�F, 10V [XL=68 Ohms at 50Hz]; C52 to 22�F, 16V.
I'thou guessing that similar changes tin be fabricated in the AM and FM detectors. This project tin become tricky since some of the needed changes can likewise affect the transmit�receive transition performance of the radio. Thus, it may exist necessary to compromise by lowering the switch diode bias electric current to about 1mA. In general, this can be washed past using 2k Ohm, instead of 1k Ohm, bias resistors.
If, after the changes are incorporated, y'all tin can withal hear RX distortion on SSB, the problem may prevarication at the
[correct-adjacent} product detector. Possible Set up: Install the missing injection-oscillator terminating-resistor at the product detector. This resistor is 62 Ohm, i/8W or 1/4W. It is soldered under the IF Unit PC lath, almost L5. The terminating-resistor is soldered to the junction of R69 and R70 and the footing foil at the edge of the PC board. If the distortion persists, yous may accept an unmatched set of Germanium product-detector diodes: D19, D20, D21, and D22. These diodes can be replaced with Schottky diodes. The product detector residue should then be checked and adjusted every bit follows: Connect an RF detector to the emitter of Q9/R77. R77 sticks up from the board at i terminate so that the test connexion can be easily made. The RF detector can be an oscilloscope, detector/probe for a DMM, or a 455KHz receiver coupled through a 10pF capacitor. With no signal input to the ANT jack, turn the RF Gain on the 440 to zero. Set up fashion to USB, IF Shift to detent. Accommodate TC1 [also installed backwards, similar TC2] for minimum RF. End of test. Reset the RF Gain control to normal.

Trouble: AGC overshoot while receiving strong SSB signals. The symptom is audio baloney on peaks only. The distortion is reduced when the RF-gain command is backed off.
Ready: On the RF Unit, nigh J13, near Q5, change R42 from 470k Ohm to 10k Ohm. This speeds upwardly the attack response of the AGC.

Trouble: TX frequency response is non the same as RX frequency response with the IF Shift control assail detent.
Fix: Connect a frequency counter to IF Unit, J26, pin 2 and ground. With the IF Shift on detent, the frequency [roughly 455kHz] of the carrier oscillator should not change between TX and RX. If the frequency changes, adjust VR7 until the frequencies are equal. VR7 is just behind the MIC pot and the elevation of the front panel; information technology is mounted on a small, PC board.

Intermittents. The interconnecting wires in the TS-440S are copper. The tin-plated unmarried-row connector pins that are crimped to these copper wires grade a dissimilar metal junction that is subject to electrolytic action due to moisture in the air. Some of these crimp connections may eventually fail to provide electrical contact due to electrolysis.
Fix: Remove the defective connector pin by depressing the ratchet-tab in the slot on the side of the connector pin and pulling the freed pin from the connector trunk. [The ratchet-tab can be depressed with a modest screwdriver.] The copper wire that protrudes past the crimp is then electrically bonded to the pivot with solder or Silver Print [GC Electronics] conductive paint. The wire/crimp junction should be inspected with a magnifier before the pin is re-inserted into the connector. If a wire/crimp junction is soldered instead of existence dabbed with conductive paint, it is difficult to foreclose the estrus from melting the plastic insulation on the wire. If soldering is the choice, the rosin flux remainder should exist removed from the pin with booze, or acetone.
The same blazon of intermittent problem may also occur in the coaxial connectors. The set up is to apply conductive paint between the crimp on the center usher pivot and the copper wire.
An intermittent frequency display or wandering SSB receive frequency can be caused by a dirty socket-to-fleck contact on IC52 in the Control Unit.

On later on production radios, IC52 may be soldered in. The aforementioned symptoms tin can also be caused by a bad solder connection on R152 in the 36MHz VCO [VCO #5] at the front-center of the PLL Unit, nearly T20. Another common problem with VCO5 is L41 [10�H] which obviously suffers from an intermittent internal connection. L41 is potted, and so the best fix may be to replace it.
A very mutual trouble with VCO5 is that the type of mucilage that is used to mechanically bond the components together appears to absorb moisture from the air (it is hygroscopic). Since water has a dielectric constant of 79, its presence can cause much grief in an RF circuit. Thus, the moisture that is absorbed into the glue tin cause the oscillator to unlock.
Gear up: Remove the original glue with solvent and a knife. If the glue is not replaced, VCO5 will exhibit microphonic bug. Some types of clear hot-mucilage seem to work well for replacing the original gum. Re-adjust VCO5 after the glue has prepare.

Problem: No straight access to RX input or RX mute. These capabilities are necessary if the 440 is to be used as a slave-receiver in conjunction with some other transceiver.
Gear up: On the IF Unit, connect a wire from the base of Q39 to J22, pin 2. Remove R176, near J22. On the X41-1610-00, (Thou/14) Switch Unit at the rear of the 440, jumper across R46 [10K Ohm]. The RX will now mute when the FSK IN jack is grounded. {FSK TX is still possible if the AFSK is fed into the MIC jack through a ten to 1 voltage divider.} The receiver input access can be brought out to the ACC 3 connector by connecting a 27 Ohm to 51 Ohm one/4W resistor to J29, pivot ii on the X41-1610-00, (N/14 ) Switch Unit of measurement. A short length of wire connects the other end of the one/4W resistor to the heart of the ACC 3 jack which is now the RX input. When slaved to another transceiver through the transverter port, this arrangement allows the operator to simultaneously listen on 2 frequencies with stereo earphones. This provides an reward to the user when working DX on split frequencies.

Problem: There is no way to adjust the reference frequency oscillator with the case on. If the frequency is adjusted with the case off, the frequency will exist unlike with the case on.
Ready: drill a 7mm to 8mm pigsty in the left side of the bottom one-half of the case. The pigsty should line up with TC1 on the PLL Unit. The position of the pigsty can exist located with the example in place. The horizontal measurement is 122mm back from the edge of the front end panel that wraps around the left side of the radio. The vertical measurement is 6mm below the edge of the top half of the case that overlaps the lesser half of the example.
To adjust TC1: [Y'all must have 10Hz readout enabled] Tune to 10.00000 MHz WWV, USB or LSB. Select Westward [wide] on the selectivity switch. Look until the tone modulation is present. Yous will hear both sidebands. If the 2 tones are not the same, adjust TC1 until the tones zerobeat.

Problem: On QSK and on SSB VOX, it does no good to back off the RF Proceeds control to reduce the nuisance of static crashes or band noise. This is because the factory stock receiver comes on total-bore whenever the TS-440S transitions from TX to RX - even if the RF Proceeds is backed off!
Fix: On the IF Unit, modify R36, near Q5, to 2M Ohm; alter R60, near Q7, to 510K Ohm. � a few standard values volition make petty difference.

Trouble: Your own transmit RF gets into the TS-440S through the EXT SP jack and causes audio rectification that is heard in the external speaker.
Fix: The sleeve/shield final on the EXT SP jack should exist bypassed to ground on the (G/14) Switch Unit of measurement with a 2nF to 20nF, 500V, disc ceramic capacitor.

If the problem is most severe on ten meters, effort 2nF [.002�F]. If the trouble is most severe on 80m or 40m, try 20nF [.02�F].

Problem: You tin hear distorted audio coming out of the internal speaker while you are transmitting on SSB.
Fix: Remove the top cover on the radio and re-position the internal speaker wires away from the area around the SSB filters. The speaker wires should be confined to the area around the speaker plug on the IF Unit of measurement. Also, continue the speaker wires abroad from the Control Unit backside the digital display.

Trouble: Key-clicks on CW. This is caused by too fast (500�S) RF output rise [brand] and fall [interruption] times.
Fix: On the IF Unit of measurement, alter C168, near Q49, to .22�F; change R225 to 33K Ohm-43K Ohm. {the factory's "fix" for this problem is OK on make only it even so clicks on break}. Unfortunately, fixing the primal-click trouble also seems to affect the full breakin make timing in the 440 which clips the start dit. Thus, if yous desire to apply the 440 on full, instead of semi, breakin, you must put up with the cardinal-clicks.

Problem: The amplifier-keying-relay, RY2 on the (N/xiv) Switch Unit, makes as well much noise, or the contacts on RY2 have burned and pitted, or all of the in a higher place. Another trouble with RY2 is that it is too wearisome to use with a full-QSK amplifier. This needless brand-delay tin crusade the amplifier to hot-switch, burning the contacts in its QSK-relays.
Set: supplant RY2 with an NPN switching transistor and ready the current pulse problem that pitted the relay contacts, which may also damage the transistor. [only works for amplifiers with positive voltage relay command]. If your amplifier uses positive 110V for the relay control, like the SB-220 and the TL-922, the relay pitting is acquired by the current pulse from the repeated shorting out of the charged .02�F bypass capacitor across the amplifier's relay control jack. The bypass-capacitor can exist removed if shielded wire is used for the interconnection cable to the transceiver. Another set is to install a 150 Ohm to 200 Ohm, 1/4W series resistor at the relay command jack to limit the belch current to a value that the relay or switching transistor can handle. The featherbed capacitor is connected to the relay-side of the resistor.

Transistor Installation Notes: The N/14 Switch Unit is located just behind the Emmet RF connector on the rear panel. The small access panel on the bottom, rear of the radio is removed to proceeds admission to the Northward/fourteen Switch Unit. 2 chassis-ground connections and one centre pin connection must exist unsoldered from the RF connector before the Switch Unit can be removed. Unplug the three connectors, remove the ii sail metal screws, and lift out the Switch Unit. Unsolder and remove RY2, D16, and the white jumper-wire and the pin that information technology plugs into. Install one 1k Ohm resistor each in place of D16 and in place of the jumper-wire and its pin. The transistor will solder in place of the relay if its full length leads are bent to fit the available holes. The emitter goes to common-ground, equally does the trace to J30, pin4 [CMC], the ground return for the relay control circuit. The base lead connects to the trace that goes to R2 {D16} and C37. The collector solders to the trace that connects to J30, pin 2 [TXC].

Problem: Poor skirt selectivity on AM.
Fix: The unsatisfactory, stock, TS-440S AM filter, CF2, tin can be directly replaced with the better performing, AM-narrow, 6KHz filter from the Trio-Kenwood R-1000 receiver. The part number of this filter is L72-0319-05 and the price is $9.ten {Dec 1989}. It is bachelor as a replacement part. Even though the improve filter has more than pin connections and is physically larger than the original filter, the IF Unit printed circuit board was designed to accept either AM filter. The design engineers must accept realized that some people would want to install a skillful AM filter.

CF2 is a pocket-size, black, cube-shaped plastic component at the rear of the IF Unit just slightly to the right of left-to-right circuit board eye. No realignment is necessary afterwards the AM filter is replaced.

Maintenance: The VFO tuning knob should be removed, after loosening the 1.5mm hex-socket fix-spiral, and the tuning shaft's bushing-bearing should exist lubricated with a modernistic semi-synthetic lubricant like Interruption Gratuitous or Tri Flow. The quantity of lubricant used should be small and the radio should exist tipped back to assist the lubricant run down into the bushing-begetting. This should be done once when the radio is new and roughly every 4-years thereafter.

Double-sideband modification for the TS-440S

Occasionally, information technology may become advantageous to use double-sideband-transmit and single-sideband receive style in order to thwart the efforts of radio sociopaths who are gratified past interfering with others. DSB-xmit/SSB-RX way gives the non-interfering stations the option of listening to the sideband that has the least amount of interference.

To install DSB capability in the TS-440S, the audio processor switch is rewired then that when the switch is depressed, the carrier is removed from the AM transmit bespeak. Without a carrier, AM becomes DSB. {The DSB modification will disable the less-than-worthless sound-PROCessor in the TS-440S.}

The modification: On the IF Unit [the top board] locate R179, which is betwixt IC4 and Connector 21 at the front, left of the excursion lath. Remove R179 and connect a jumper wire from the correct hand, empty solder-pad hole on the circuit lath [collector of Q41] to the junction of D45 and R196, which is straight back on the circuit lath, just to the left of IC5; nearly 4cm from the rear of the circuit board.

To enable DSB transmit/SSB receive, "SPLIT" performance is utilized:

1. Program VFO A=B.
2. Program VFO A for either USB or LSB, depending on which one has the least interference.
3. Plan VFO B for AM and push the PROC [DSB] switch in to remove the AM carrier.
4. Select VFO A.
5. Programme SPLIT operation. The 440 volition now mind on VFO A and transmiton VFO B.
6. Set the carrier control straight up to position #five [12 o'clock].
7. While transmitting, arrange the MIC gain control for a pocket-size amount of ALC. This keeps the DSB bandwidth to a minimum.

While listening [VFO A], information technology may be necessary to select the sideband that has the least amount of interference. If your friends are likewise transmitting on DSB, y'all may be able to go on communicating, despite the efforts of those who would like to spoil the enjoyment of others.

>>>DSB should not be used unless the other sideband is vacant. If the interfering station or stations tin cause the group that they are interfering with to interfere with a third group, it will definitely make their day.

Virtually jammers relish beingness talked about, either positively of negatively. This is why they usually switch back and along between receive and transmit. If you want a jammer to stick around, talk almost him. Stupid insults unremarkably piece of work best.

Kenwood Ts-440s Internal Antenna Tuner Repair?,

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