chris451rr
Member
I have 3 of the IC-R7100 receivers. I noticed on all of them at different times,
the frequency drifts and is off frequency. Also sensitivity is down.
And you can 're-align' all the oscillators and still have this problem. First you must check all the voltages inside.
It is not an oscillator problem, it is a voltage problem. The radio has a DC DC converter similar to the one in the IC-R7000 the IC-751, (the 7000 and 7100 are very similar except the display processor and the way it works the bands high and low.
Usin the ICR7100_Service.pdf you can see the DC DC circuit. It has a +24 and a -12v regulator. After the regulator and a filter you wind up with J6 +21.6, +9, -7, and -12v. Your radio is sick if these voltages are low such as the +24 being 18v or less.
This is caused by leaked out capacitors that have gone open circuit, C21 and C22. You take off the top radio cover(carful of the speaker plug, disconnect before lifting up much. There is another cover over the DC DC unit and the whole assembly has to be lifted up and the bottom EMI cover desoldered to get to the bottom of these two capacitors.
If you have a scope you will see spikes up to 41v at D6 and no filtering at the cathode.
I have replaced these two capacitors on all 3 of these receivers.
If your radio is not working well its most likely bad capacitors. Once this radio has all its voltages and tuned to correct frequencies per the manual, it 'hears' so much better than SDR's or hand held scanners on the same antennas.
Using an SDR with a DC block does not have the same performance, noisier there.
I use CIV-Commander but it does not deal with the internal memories (900 of them). I can read all 3 on the same bus but CIV commander only handles one radio at a time. Not bad for a 30 year old radio.
the frequency drifts and is off frequency. Also sensitivity is down.
And you can 're-align' all the oscillators and still have this problem. First you must check all the voltages inside.
It is not an oscillator problem, it is a voltage problem. The radio has a DC DC converter similar to the one in the IC-R7000 the IC-751, (the 7000 and 7100 are very similar except the display processor and the way it works the bands high and low.
Usin the ICR7100_Service.pdf you can see the DC DC circuit. It has a +24 and a -12v regulator. After the regulator and a filter you wind up with J6 +21.6, +9, -7, and -12v. Your radio is sick if these voltages are low such as the +24 being 18v or less.
This is caused by leaked out capacitors that have gone open circuit, C21 and C22. You take off the top radio cover(carful of the speaker plug, disconnect before lifting up much. There is another cover over the DC DC unit and the whole assembly has to be lifted up and the bottom EMI cover desoldered to get to the bottom of these two capacitors.
If you have a scope you will see spikes up to 41v at D6 and no filtering at the cathode.
I have replaced these two capacitors on all 3 of these receivers.
If your radio is not working well its most likely bad capacitors. Once this radio has all its voltages and tuned to correct frequencies per the manual, it 'hears' so much better than SDR's or hand held scanners on the same antennas.
Using an SDR with a DC block does not have the same performance, noisier there.
I use CIV-Commander but it does not deal with the internal memories (900 of them). I can read all 3 on the same bus but CIV commander only handles one radio at a time. Not bad for a 30 year old radio.
