Symptom:
Proper microphone gain/ALC readings cannot be obtained unless the user adjusts the TX GAIN potentiometer on the rear of the DSP-100. This irregularity is caused of the DSP-100 MIC amplifier (IC-5).

Corrective action:
Remove capacitor C200 from the IF unit on the transceiver, and replace it with R300, a chip jumper wire.

Parts required:

Qty   Description                          Kenwood Part No.  Circuit description
 1    Chip jumper                          R92-0670-05       R300

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

The 2SC2509 driver transistor are no longer available. They have been discontinued by the manufacturer. A substitute transistor (2SC3133) is available but requires some minor circuit changes. These changes are detailed below.

Parts required:

Qty   Description                          Kenwood Part No.  Circuit description
 2    Driver transistor                    2SC3133           Q2, Q3
 2    330 ohm 1 watt carbon resistor       RC05GF2H331J      R8, R9
 1    .047 µF ceramic capacitor            C91-0119-05       C2
 2    220 pF ceramic capacitor             CC45SL2H221J      C64, C65
 1    560 pF ceramic capacitor             CC45SL2H561J      C63

Note: C64 and C65 should be soldered directly to the collector and emitter pins of the final transistor Q4 and Q5.

Symptom:
When tuning the Main Encoder of the TS-450S/690S with bare hands you may encounter a "scratching" noise in the speaker if an antenna with a high SWR is used. If gloves are worn no problem is encountered. This occurs because the shaft of the encoder is not grounded.

Countermeasure: Replace the Main Encoder with one that has a grounded shaft.

Parts required:

Qty   Description                          Part No.
 1    Main encoder                         W02-1836-05
 2    Mounting screws                      N90-3006-46

Note: You must use the new mounting screws listed above with the replacement encoder.

Note: This bulletin supercedes bulletin ASB-994, dated 10 April, 1992.

We have received several reports of distorted transmitter audio when using a TNC controller such as the AEA PK-232 or Kantronic KAM, etc. The symptom will generally disappear if the transceiver and TNC units are powered from different sources.

Cause:
The audio output level form the TNC is generally too high and causes overload of the microphone amplifier circuit. In previous models such as the TS-440S the incoming TNC audio was inserted after the microphone amplifier. With the TS-850S it is inserted before the microphone amplifier. Just moving the insertion point to the output of the circuit is satisfactory since the drive level for FM packet is higher then that required for SSB.

Procedure:

1. Add a 10 dB attenuator to the PKD line on the IF unit (X48-3090-XX). This will prevent overmodulation of the microphone input circuit.
   1. Change chip resistor R233 from 10 Kohm to 18 Kohm (RK73FB2A183J)
   2. Change chip resistor R234 from 1 Kohm to 8.2 Kohm (RK73FB2A822J).
   3. Delete chip capacitor C173 (100 pF) and add chip resistor R299, 1.5 Kohm (RK73FB2A152J).
   
   
    
2. Add the following note to page 35 and 37 of the Instruction manual.
   
    
3. When adjusting for proper ALC levels with an AFSK RTTY terminal or Packet TNC terminal you should adjust VR-13 on the IF Unit for a reading similar to the one shown in the accompanying diagram.
   
   Note: The transceiver and RTTY or TNC terminal should use separate power supplies, in order to prevent RFI (Radio Frequency Interference).

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

We have received several reports concerning the transmit audio quality of this unit. Several reporters noted that the signal sounded "hard" or had a reduced bandwidth, while others noted a difference in the noise quality when switching between USB and LSB. We noticed a significant difference between the output power in LSB and USB on some of these sets.

Cause:
Improper adjustment of the 8.83 MHz tuning coils (L73, L76) on the RF unit (X44-3130-00) can cause these symptoms. The coils have two tuning points. One is reached when the tuning slug project above the surface of the coilk form. When tuned in this manner the bandwidth becomes narrow then normal and causes the symptoms noted above.

Alignment procedure:

1. Adjustment should be performed with the YK-88S1 (2.4 KHz) filter in line. If this filter is not preset you should select the THRU position for the 8.83 MHz IF.
   
    
2. Adjust L73 and L76 according to the instructions provided in the service manual (Item 6 of the Receiver adjustment). Ensure that the slug are preset well down in the coil form, then adjust for peak. You should reach this point before the top of the slug exist the coil form.
   
    
3. Next, readjust L74 and L75 (Item 8 of the Receiver adjustment).
   1. Select the 6 KHz filter for both the 8.83 MHz IF and the 455 KHz IF.
   2. Select a dial frequency of 14.100.4 MHz.
   3. Select the USB mode.
   4. Adjust L74 and L75 for maximum.
   5. Select the LSB mode.
   6. Readjust L74 and L75 for maximum.
   7. Repeat steps 3c - 3f several times until you obtain a difference of 2 dB or less in the AF output when switching between USB and LSB.
   
   
    
4. Check Item 14, CAR point adjustment (Transmitter section) Menu items 11 and 12, and confirm that the transmitter power is equal for USB and LSB.

The TS-450/690 may not calibrate properly against WWW (JJY) when using the calibration cable that is supplied with early versions of these sets, (serial numbers below 311xxxx) and when an antenna that is shorted for DC is used. A dipole with a balun is a prime example of a DC shorted wire. A minor circuit modification that adds a 100 pF isolation capacitor should also be performed. Please refer to the diagrams below for modification notes.

Parts required:

E37-0280-05      Calibration cable assembly         1 Ea.
CK73FCH1H101J    100 pF capacitor                   1 Ea.

1. Set your meter on the radio to read ALC
2. PK232 OWNERS: if alsso using a VHF tranceiver, adjust the AFSK level for proper VHF operation as expalained in chapter 3 of the operating manual.If not adjust for proper SSB operation.
   
   DSP - 1232 / DSP - 2232 Owners: Adjust the appropriate AFSK level control for proper SSB operation as expalined in chapter 3 of the operating manual.
3. Place the TNC in calibrate mode and press K to key the radio.
4. Adjust VR-13 on the TS-450 or VR-18 on the TS-850 so that the meter "Just comes off the peg" as described in the section titled "SSB Tranciever Final Adjustments" (in the TNC operating manual).
5. Press Q to quit the CALIBRATE mode