Kenwood TH-25A Instruction Manual page 20

On the TH-26AT this is just a bare jumper wire, TH-45AT ???, TH75A it is a green wire labeled W1.
Removing or lifting D4 on the TH-75A extends TX from 136-174Mhz and 335-512Mhz.
On the TH-26/TH-46 models this would be 136-174Mhz and 335-512Mhz respectively.
TH-25/45 W/TSU-6 Tone alert improvements
When using the TH-25/45 in combination with the TSU-6 you may experience erratic operation of the
tone alert function. This may be due to an incoming signal that is over-modulated, distorted, or noisy. The
following modification will correct this tendency.
Required parts:
22 µF, 6.3V electrolytic capacitor
56 Kohm, 1/8 watt carbon resistor
Diode
1. Remove the TSU-6 from the TH-25/45 (refer to theTH-25/45 instruction manual for details).
2. Cut the blue wire (pin # 4) approximately 5 mm from the connector for the TSU-6.
3. Solder the components to the blue wire and ground as shown in figure 1. Note that the cathode side
of the diode goes toward the TSU-6 connector. Use the leg of the VCO shield to ground the
negative side of the capacitor.
4. Insulate the components with electrical tape to prevent shorting.
5. Install the TSU-6 in the tH-25/45. Route the components so that the battery terminal plate does not
bow when installed.
part # CE04CW0J220J
part # RD14BB2B563J
part # 1SS133
Figure 1.
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