This page covers modifications to the Kenwood TR-9130 (2metre) and TR-9500 (70cm) All-Mode transceivers.

I replaced the white incandescant lamps with a set of green LEDs, to reduce power consumption and to also
reduce heat build up from the lamp, plus improve reliability, as eventually the incandescant lamp will die,
either from fatigue or vibration. Plus the signal meter easier to read in a dark room when backlit with green,
such as operating portable at night in a dark location. Running the incandescant lamp considerably raised
the temperature  of the transceiver, with the green LEDs they run much cooler on receive.

I replaced the series resistor with a 1/8th watt version, I tried different values to give me the correct
amount of light for 13.8v input, the signal meter was quite easy to disassemble as it held togther with
sticky tape between the white plastic and the clear plastic pieces. I desoldered the old incadescant lamp
and soldered the LED string in its place.

I also noted these radios have a fair bit of drift in terms of frequency stability from cold to normal
room temperature operation, I fixed that by bogging the sensitive components in the VCO's with non-conductive
heat glue, instead of drifting a few kHz, it down to the order of a few hundred Hz now.

And it was interesting that the TR-9130 has a Auxillary socket with output to drive a 2metre linear amp
(PTT relay control), so I added a 3.5mm socket to the rear of the TR-9500 (in the Aux position) to provide
the same control to drive a 70cm linear amp.

I re-tuned the Rx front ends and TX PA's for 144.200  and 432.200 respectively, to give maximum power output
and maximum receive sensitivity at the "weak-signal" end of those bands, as I not interested in running FM
and repeaters in these two transceivers. Now these receivers can give a IC-910 a run for their money, in
terms of receive sensitivity at this end of the 2m and 70cm bands.

If I added a good reference oscillator with GPS lock or Rubidium reference, then it will become frequency
accurate and a very good set of transceivers for "weak signal" DXing.

Here are the photos:




soldered together four green leds, in series, to make a string of LEDs to backlight the signal meter.

I ground down the bezels, so as to spray the light evenly, instead of focused into a single spot, plus

so that they fit into the meter.





this is the soldered side of the LEDs and also the removed incandescant lamp in a greep sleeve in the background.





this shows the signal meter during removal





a view of the LEDs mounted on the lamp board





a close vertical view of the LEDs mounted on the lamp board





an overview of the LEDs mounted on the lamp board





This is the TR-9130 prior to conversion to green LED backlit signal meter





This is the TR-9500 after the conversion to green LED backlit signal meter





top view comparing the TR-9130 and TR-9500 transceivers





bottom view comparing the TR-9130 and TR-9500 transceivers





just a closer open view of the top of the Kenwood TR-9500 transceiver










 
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