Originally Posted by James (Post 47011)

I wish to repair my own Kenwood TS-450S-AT and to begin from
somewhere, I'd like to know what other 450's users think of the
current situation:

1) When I power the rig, I have no audio at all and no
trasmitting. The display shows a row of dots. If I move the
main dial, the frequency appears normally, but if I release it,
after half a second the dots appear again.

2) Some other times, when I give power I have both audio and
trasmitting and the display works well, but the audio in SSB/CW
modes is totally distorted, while it is ok in AM/FM modes.
However after 5-20 minutes of rx, the situation becomes that
described at point 1.

3) I have read of the battery problem in the 450, so I found
the lithium battery and measured it. It gives 3.28 V, is that
normal? Since the rig is approaching ten years I think I will
change it anyway, but I don't know if it is a problem now!

4) On the bottom side of the rig, near the place for the 455 kHz
cw filter (I have the 8.83 one, so this place is empty), there
is a 3-wire connector labeled "W3". The short cable, with a
similar connector on the other side, is attached to... nothing.
But I don't see any place to attach it, even if I look at the
whole board. Unfortunately I lack the 450/690 service manual
and I did not find this connector on the istruction manual
schemes. This MAY be normal, though.

My conclusions, for now:

a) When things are ok, except for SSB/CW, the problem should
arise in the second IF at 455 kHz. Either the CAR Unit does
not give a correct 455 kHz carrier or something is wrong in
the IF mixer chip or near it. In fact this chip is used only
in ssb/cw/fsk modes.

b) When the rig is almost dead, perhaps there is something wrong
in the digital/display unit. Lithium battery? Some digital chip,
which one?

c) Also the mere power could be a problem. My supply, 13.8 V 40 A
max, looks good, but internally there are circuits to obtain the
different voltages required and these could be damaged.


I am mainly looking for the service manual (someone has scanned
it?), but all other advices are welcome.

James