From: "Carel, PA0CMU" 
Subject: [drakelist] TR7 mode switch thumb


"Carel, PA0CMU"  made an utterence to
the drakelist gang
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Hi all,

From the estate of a friend, PA3BBT, I got a TR7 (serial no. 3157) and PS7.
All his amateur equipment was kept in boxes for nearly seven years and
needed a serious cleaning. Two of my friends do have a TR7(serial no. 7???)
and TR7A (serial no. 11178) too, so we can compare differences between
the rigs.

Both TR7's produce a fairly loud "thumb" in the speaker when turning
the mode switch to CW, regardless one switches from RTTY to CW or
from LSB to CW mode. The same thumb appears when the AM mode is
selected. The TR7A on the other hand, produces a smooth, thumbless
switching between all modes. Despite all internet info we could not find
any modification for this fault. Does anyone have some info on that?
Is it a bug, or just "normal" for the TR7.

In my TR7 the first low pass filter (L1701 - L1702) is omitted, but in the
other TR7 and TR7A all components are mounted.
Does anyone know the values and toroid material of L1701 and L1702?

We also found out that there is missing a copper trace on the noise
blanker PCB. The connection between pin 1 of the MC1350 and L812
is omitted on both available NB boards! One of the noise blankers didn't
work (never did?) but was fine after placing about 5mm copper wire
between both pads.

73, Carel - PA0CMU.

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