2.1 Troubleshooting a CI-V level converter

Probably you have built a CI-V level converter, following one of the many examples in the previous section. And now it does not work. Then this section is for you, it gives some hints on where to start looking.

So you have an interface, and it is not working. Following this step-by-step guide should help to pinpoint the cause. All you need is a simple multimeter, digital or analog. An oscilloscope is nice to have but not required.

Step 1 - Check the rig CI-V output when idle

First, make a measurement of the voltage supplied by the rig on the CI-V line. To do that, unplug the cable leading from the rig to the converter. Leave it plugged into the rigs CI-V jack. At the now open end (probably a 3.5mm mini plug, depending on the interface) you should measure about +5V, but anything from +4.2V to 5.1V is also ok. Measurement is done from the data signal (tip of 3.5mm plug) against ground (sleeve) of the rig.

Pass: +4.2 to +5.1 Volts; proceed to step 2.

Fail: under +4 Volts. The simple solution would be a short in the cable, probably in one of the plugs. Check with your ohm-meter.

If the cable is ok: Bad news. Probably the internal CI-V driver is not working. The only solution: check the internal circuitry which drives the CI-V output. And this means probably that the rig has to be serviced by Icom or a dealer. But I have never seen a real failure of a CI-V circuit, even after a short circuit.

Step 2 - Check the rig CI-V output when tuning

Now, with the multi meter still at the open ended cable, rotate the frequency dial. While turning the dial the voltage should be something around +2 to +3V. This is due to the signal rapidly changing between +5 and 0V, but your multimeter is too slow to show this. An oscilloscope would show a nice rectangular digital signal.

Pass: Voltage around +2 to +3V when turning the dial, proceed to step 3.

Fail: Voltage does not change (stays at +5V or so) when rotating the dial. This can have a simple reason - the so called CI-V Transceive function of the rig is not turned on. Only with this option turned on the rig sends out data when changing the frequency. On newer rigs you can change the setting of CI-V Transceive with some menu option; on older rigs it requires re-soldering some diodes. Please check your documentation.

If with CI-V Transceive set to on the voltage still does not change from +5V, again something is probably wrong with the CI-V driver circuit in the rig. Bad news, but unlikely.

Step 3 - Check the CI-V converter input

Now connect the cable from the rig to the input of the CI-V converter. make sure that only one rig is connected, in case that you have a converter which allows connections to multiple rigs.

Again you should measure the voltage on the CI-V line, best done by opening one of the plugs and measuring directly at the soldering pads of the plug. The results should be the same as above: around +5V when idle, +2 to +3V when rotating the dial. If you see a slightly higher voltage then before, that's ok. It's due to the circuit of the converter which pulls the line voltage up a little bit.

To be continued...