[Kenwood] TS950SDX stuck in transmit mode

[rbethman]

Peter,

You keep using 12VDC only.

TTL (Transistor to Transistor Logic) circuits use 5VDC for control.

Applying ONLY 12VDC will always have undesired results.

Search schematic for what voltages are being applied on which pins.

Do you have the Service Manual?  It will be VERY useful in this problem 
resolution.

73, Bob - N0DGN

On 2/1/2013 5:16 AM, Peter Ravn wrote:
> Since November my TS950SDX has been stuck in transmit mode with no output at
> all. To test the T/R antenna relay I had applied 12 V to the relay from an
> external PS without unplugging the connectors to the filter board, which of
> course was unwise. When I switched on the radio again, the transceiver was
> stuck in TRANSMIT mode without any indication of output. When the AT was engaged,
> the SWR on the internal meter would run out of scale. There was no indication of
> Ic on the internal meter no matter the mode.
>
> After a long search I found a shorted transistor (Q152) in the TRX sub
> board (X59-3680-00) in the control unit. The short was suspected to have been
> caused by the above mentioned blunder.
>
> Today the board was taken out and the shorted transistor replaced. Before
> mounting the board, I tested it to see if it would switch between RX and TX.
> It did. But when the board was reinstalled, the TS950SDX was still stuck in
> transmit mode with no output, so apparently the problem is somewhere else.
>
> Any idea will be appreciated.
>
> Thanks.
>
> 73 Peter
>
> OZ8CTH
>