[Kenwood] TR2400

[Dr. Gerald N. Johnson, electrical engineer]

Its been about ten years since I had a TR-2400 and shop manual. I'm
thinking that center was positive on the power plug. It would be
positive (red) to the switch. And positive (yellow) to the charging
connector. On the battery plug. Power from outside (yellow) direct to
the battery, then power to the radio (red) from the other positive pins
of the three pin connector. That way the battery is in place to protect
the radio from high voltage.

A common problem with the TR-2400 is applying 12 volts direct to the
external power connector. There is no current limiting in the radio so
that fries stuff in the battery circuit as well as the battery. The
radio itself is not rated for 14 volt operation, just 11.6 as I recall.
The damage from 12 volts can be close to the damage caused by reverse
polarity. Typically on 12 - 14 volts the radio gets very hot and
temporarily turns the LCD display black. If the LCD display wasn't
replaced about 12 years ago, it may already be black from having leaked
out the liquid.

A choke in the charging circuit is probably not a critical value, I'd
suggest 1.8 microhenries (as typically being self resonant near 144
MHz).

73, Jerry, K0CQ
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.