Modifications for the Kenwood TS-2400

TS-2400 out-of-band mod

Locate the rx unit.
Cut the diodes D32 and D33 located inside the DTMF ic.
Is this simple or what?!
TR-2400 Unwanted Noise: Tone or burst at TX


For complaints of a tone burst type noise, or simply a noise, at initial key down, suspect either a broken losse component, or incorrect valued component on the RX TX unit.

On the RX TX unit, Q16 emitter, check C82, a 33 uf tantalum cap for broken connection.

If you find a 22 uf cap at C82 replace it with a 33 uf cap.
TR-2400 Display or Keyboard trouble



An intermittent or blank digit may be caused by either a broken lead, or intermittently shorting lead on the PLL unit.

On the PLL unit, look in the area of Q12, the touchtone generator. Between Q12 and the board edge locate the D1-D4 lines. Inspect this area for either an open (Broken) lead, or shorted (pinched) lead. Repair as necessary, and check lead dress before reassembly.


An intermittent or inoperative keyboard row or column may be caused by a torn or pinched lead, or a cracked diode.

Again, in the area of Q12, inspect the "T" and "Y" lines for shorts or open connections, and inspect diodes D19-D26 for physical breakage.
TR-2400 RX low, INtermittent, or distorted


For any of the above complaints, suspect a broken loose component in the RX IF or audio output circuit on the RX TX unit. Simply pull up on the leads and resolder.

Adjacent to Q9, the audio output IC, find C49, a 1uf cap. If broken loose from the board, audio output may be down, while current consumption may be up from the normal 30mA to about 100mA due to the audio output amp oscillating.

Adjacent to L10, the discriminator, locate C33, a .033uf cap. If this component is broken loose, audio output may be up approximately 6 dB with excessive high frequency audio response.

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