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adjustment, other than if the final RF output transistor should need to be
replaced (which would also be rare). The sidetone level pot may be adjusted to
set the level your liking, and the low battery level pot can be set to a level
consistent with the battery type you use. This level is usually set to about 9.5 volts
on factory wired units. To access these adjustments, the plastic case bottom must
be removed. To do this, remove the four black screws from the case front panel,
and remove the board set along with the case top half by lifting on the left side of
the panel and maneuvering the BNC connector through its exit hole. All five
internal adjustments will now be accessible. The sidetone level adjustment
control is labeled on the left side of the lower board next to the power jack. The
PA bias and battery detector adjustments are labeled on the rear of the lower
board. To set the low battery point, adjust the input DC voltage to the battery
voltage you wish to have the alarm flash, and adjust the low battery pot until the
red LED alarm LED blinks. Be careful not to adjust the bias pot by mistake! See the
on-line building procedures for instructions on setting the PA bias. The blue signal
strength LED sensitivity pot is located between the bias and battery voltage
warning adjustment pots and is attached to the upper board. Normally the pot is
set for a faint glow of the blue signal quality LED with the RF gain control fully
counterclockwise. The audio bandpass filter adjustment is labeled on the lower
board at the front of the unit. The pot is adjusted for maximum sidetone audio
volume while in narrow CW mode. This will be very close to the center of the
rotational range.
TR-35 Connector Wiring
Phones Jack: The Phones (speaker) jack will work with a standard 3.5mm mono
plug. A conventionally wired stereo plug may also be used. Note that the speaker
ground connection must be made to the ring terminal of a stereo plug. Standard
stereo headphones with a 3.5mm plug will work just fine. Do not use a stereo plug
where the tip and ring connections are tied together. This will cause a short to
ground and burn up the audio power amplifier!
Key Jack: The Key jack will work with either a mono or a stereo 3.5mm plug. The
tip and ground shell connections are used. There is no connection to the Key jack
ring terminal inside the TR-35