[Lowfer] Can I bypass the BCB attenuator in my TS-450S

[Mitch Powell]

> Greetings All: Has anyone found and done a sucessful
> bypass mod for the B.C. band attenuator on a Kenwood
> TS-450S ? That 25dB is really a signal killer. I have
> the mod for the TS-850S but I'm not sure if the RF
> boards are the same having no schematic for the 850.


Andy - I have the schematic for the 450 and the 850 - the rf section is
identical.  The mod (bypassing R7 and R8 ) on the 0.5 - 1.6 MHz section is
identical .... I would imagine they have used the same RF boards.

I have an 850S and I know that on the LF ( < 500 kHz) it is very good .

The circuit of that input has no attenuation resistive network - apparently
the reason it is so good.

Hope that helps.

Here is the MOD
Mod 4 ‹ Better 0.5-1.6 MHz Sensitivity

The TS-850 receiver has excellent dynamic range and immunity to overload.
Nevertheless, Kenwood placed a 26 dB attenuator after the 0.5-1.6 MHz
bandpass filter. This means the receiver has less AM band sensitivity than
the average 1950s-era kitchen radio.

Invert the ¹850, remove the bottom cover and the metal shield on the RF
board. Find the labels identifying L8 and L9 in the left rear corner of the
board, then find the two copper-clad holes (solder points) next to the label
³.5-1.6², very close to L9. Carefully remove the plugs and ribbon cables to
the RF board and unscrew the board from its mounts. Form a small ³U² jumper
of fine bare wire to connect the two copper-clad holes. Lift the RF board
and solder the ends of the wire to the hole pads on the underside of the
board, thereby bypassing attenuator resistors R7 and R8. This requires fine
solder and a very fine, clean, soldering iron tip. Carefully refasten and
reconnect the RF board.

73

Mitch