Modifications for the Kenwood TS-930

TS-930S PLL Unlock

Some users of the TS-930S have reported a problem where the PLL will sometimes not lock (digital display does not come on) if the power switch is turned off and on while xx.499.9 MHz is displayed, after the unit has warmed up. This may occur also in the FSK mode.

This may be caused by detuning of VCO-2 and VCO3 in the PLL unit (X50-1880-00). This may be cured by a simple increase in the voltage obtained in the PLL alignment procedure. Make the following change in your service manual.

Service Manual page 58.

3. VCO-3 T14 change 3.7v to read 4.2 vdc
4. VCO-2 T15 change 3.0v to read 3.5 vdc

Be sure to adjust T14 and T15 of VCO-2 and VCO3 whenever a PLL related circuit is serviced.
This change applies to units before S/N 306XXXX.
Installation time for this change is 1/2 hour or less.
TS-930S Service Notes on AT-930

Some of the symptoms and cures for troubles that have been encountered with the AT-930 are listed below.
  1. The motors do not stop on all bands.

    Possible causes:
    a. Cold solder joint of platee VCJ wire.
    b. Cold solder joint of L18 lead.
    c. Cold solder joint of the wire between pin 13 of Q39 and R139, D33 and R138.

  2. The motors do not stop on the 7 MHz band.

    Possible Cause:
    The rotor of VC2 contacts (shorts against) the stator.

  3. The motors do not stop on the 28 MHz band.

    Possible Cause:
    Cold solder joint between D33 and R84

  4. The AUTO mode does not reset.

    Possible Cause:
    The wire from R138, R139 and D33 may touch Q39 pin 14.

  5. The motor stop when SWR is at Maximum.

    Possible Cause:
    The wire from R138, R139 and D33 touches Q39 pin 14 and the foil is broken around VC1.

TS-930S Intermittent TX Power Output

The following procedure should correct any tendency of the TS-930S to exhibit intermittent TX power output. Most of the reported cases of thsi nature have been traced to poor contact of one or more plated thru holes mentioned below. Careful adherence to this procedure should prevent reoccurrance of this symptom.

  1. Remove the top and bottom covers.
  2. Remove the 10 screws securing the final unit to the chassis.
  3. Disconnect all cable assemblies from the final assembly, and remove it from the radio. The fan motor cable may have to be removed for easy access.
  4. Remove all Final Unit PC board screws and turn the circuit board foil side up.
  5. Desolder Q6, D2, and the plated-thru hole connecting the foils from R20 and Q8 base together (between T2 and VR1). Do not remove the components!
  6. Carefully remove the green solder resistant coating from the immediate areas of these six points, so that there is bare copper foill up to and surrounding the eyelets.
  7. Carefully resolder these six points, and those listed below:
    Q1 Emitter and base
    D4 anode and cathode
    Q2 Emitter and base
    Q3 Emitter and Base
    Q7 Emitter and Base
    Q4 and Q5 Base and collectors
    Plated-thru hole between C36 and C15
    (2) Plated-thru hole sby the molex connector.
    Check and resolder the input and output coax connectors.
  8. Double check your work to ensure that there are no solder bridges or splashes.
  9. Check the value of R19. If it is not 6.8 K ohms, change it so it is.
  10. Reinstall the final assembly, and readjust the idle bias currents of the driver and final transistors in accordance with Service Bulletin 867.
Ensure that no cables are pinched between the final assembly and chassis when reinstalling the final unit. The fan cable is especially vulnerable, so pay close attention!
Tuning Mods TM-930

  1. The resolution of the main tuning digital readout can be increased from 100Hz to 10Hz. No digits are lost since the readout has the extra digit for this purpose. This change can be accomplished by grounding pin 1 of connector 8 on the digital unit PCB.
  2. The tuning rate is 10KHz per revolution of the main tuning knob.
    The tuning rate can be changed to 5KHz per revolution by removing or lifting one end of diode D-13 on the digital unit PCB.
  3. Note that the black marks on the tuning knob itself are exactly 500Hz apart. The knob can be "corrected" by tuning in an exact frequency, such as 10,000.00KHz, pressing the DIAL LOCK switch, then turning the knob to line up a black line. As long as you don't spin the dial too fast, it will track nicely from one end to the other. With the slow rate tuning modification above, the dial increments become 250Hz per division.
  4. You may desire to switch the new reduced tuning rate on and off. For example, you can select the new rate on just VFO B by using an unused section of the FUNCTION switch to make or break the circuit on diode D-13. Another pssibility is to use the display DIM switch.
  5. There are an additional 8 memories available. These can be util- ized by grounding pin 5 of connector 7 on the digital unit PCB. This lead is designated as "M3". The additional memories can be selected by using the unused contac on the FUNCTION switch or by adding a new switch.

Amtor keying mod

  1. Look at the signal board and locate C500. C500 is an electrolytic 4.7uF located near the center of the board (if viewed with the radio upside down with the front facing you) near connector 30.
  2. Remove this capacitor by carefully twisting it with a pair of needle nosed pliers. This capacitor cannot be easily removed any other way without completely disassembling the radio. The function of this capacitor was to de-bounce the PTT switch and is a big reason why the TS-930 will not work satisfactorily in AMTOR mode.
  3. Next, locate R476 wich is on the same board as above and is positioned just above the large CW filter. The lead that is exposed needs to be grounded. An easy way to do this is to locate R474 which is right next to R476 and scrape away some of the insulation from both of the exposed leads, then solder a bridge between them.

TS-930S CW Pitch Tone Shift


Some users of the TS-930S have reported a slight change in the CW pitch tone when the MONI switch is turned ON and OFF.

This may be corrected by changing the following components:

On the Signal unit (X57-1000-XX) change R826 from a 1 K ohm resistor to a 10 K ohm resistor and remove C601, a .022uF capacitor from the foil side of the circuit board.

This change is applicable to units before serial number 3070221 only.
TS-930S 15 Meter Internal Beat Tone


Some users have reported an internal beat tone that appears every 10 KHz , when operating in the range of 20.000 to 21.500 MHz. Apparently the RV terminal of Switch Unit H is being affected by the 1st loop of the PLL unit. The cure is relatively simple. Add a .01uF 50v Disk ceramic capacitor from the RV terminal to ground.
TS-930S RF Feedback


For reports of RF feedback from the external speaker, especially when using a vertical antenna, or a linear amplifier, check for correct installation of capacitor C16 on the EXT SPKR jack.

C16 should go from ground to the white wire on the opposite side of the jack. Some units have the capacitor soldered to the middle terminal in error!

This bulletin is applicable to radios with serial numbers prior to 3070420.
TS-930S SSB TX Tone Quality


The transmitted audio tonal quality of the TS-930S may be improved by the following procedure:

In the TS-930S Service Manual page 64, make the following change:
5. 100 W Final Bias VR2 adjust for 70 ma
                    VR1 adjust for 1.3A
This change is applicable to units with serial numbers prior to S/N 3080001.
B>Error in the operator's manual of the DIGITAL UNIT pin

Note: In the operator's manual supplied with the 930, there is an error on one of the drawings. On the upper left corner of the DIGITAL UNIT schematic locate connector 8. The lead designations are as follows (note that some of the designations do not appear on this sheet so you can add them to the drawing):
        Pin     Desig.
         1       100
         2       MU
         3       SCN
         4       M2
         5       MIN
         6       FSK
         7       B2
         8       FT
On the main drawing, called SCHEMATIC DIAGRAM, the pin numbers shown on connector 8 are reversed from the way they are numbered on the DIGITAL UNIT schematic. In the following changes, I am assuming that the numbering on the DIGITAL UNIT sheet is correct. In any event, it will be obvious which end is which since the end pin is vacant.

Go Back To The Kenwood Mods Page

Go Back To The Main Modifications Page

Go Back To The CB / HAM Radio Main Page

Go Back To The Main Home Page

Copyright © The Defpom 1997-2008