IC-746 - a problem that wasn't!

Well, my heart sank yesterday as I connected up to the 2m slimjim atop my roof and tried to send FT8 with the new ICOM IC-746.

Nothing happened!

I tried to work through everything, but got nowhere.  The data transmission works perfectly on all bands except 144MHz - the very band I'd bought the 746 for!  If I manually pressed 'Transmit' on the front panel, the data went out just fine.  So it seemed to be a TX-trigger issue of some sort.

I could find no help on the internet, and so resorted to asking for help from ICOM in the UK.

Outstanding help from Icom.

I've specifically written this blogpost to highlight to others the incredible fact that ICOM actually phoned me back within 30 minutes of sending an enquiry to their servicing team.  How many companies bother to answer at all these days, let alone so quickly?

A very friendly technician told me it was simply a case of having a different transmit trigger line for VHF (the so-called 'HSEND' for HF, and 'VSEND' for VHF). 

With just one simple, free support callback for a second-hand rig, ICOM have shown themselves to be a rig maker worth taking very seriously in my next new purchase.  Take note, other makers!

Three others who must be thanked for kindly helping me when they might reasonably have just turned their eyes skyward at another fool asking for assistance were:

• Technofix, providers of just about any data/CAT cable you can imagine

• Neil, owner of low noise data interfaces and accessories at ZLP Electronics

• Sam Hayward at UK ham radio outlet, Radioworld

UPDATE:

I eventually found some useful information online, courtesy of N5KBP, Marty Duplissey.  My colleague PE4BAS rightly says there is pinout information in the manual (p.72), but I wanted to triple-check I wouldn't get it all wrong and damage the rig.  One thing to remember is that, when looking at the pinout diagrams, you are looking at the socket as it appears at the rear of the rig, not the plug you are trying to wire!

Here's what N5KBP kindly submitted, which may help others in future (or help me remember when I do it again!)

'All the audio goes through ACC1 regardless of band. Pin 4 is audio from computer to radio, Pin 5 is audio from radio to computer, pin 2 is ground and pin 3 is ground to transmit on HF. On ACC2 the only pin you will use is pin 6 for VHF ground to transmit.  All you need to do is to wire pin 6 on ACC2 in parallel with pin 3 on ACC1.   On my setup I built the ACC1 8 pin connection then just ran a single wire from pin 3 on it out to pin 6 on a 7 pin din plug for the ACC2 to enable transmit for VHF.  Basically get it going on HF then add the wire to ACC2 to enable VHF transmit.'

It turns out that it's quite difficult to solder another wire onto pin 3.  You need very thin gauge wire, first of all.  I found it a bit easier, although not ideal, to cut into the cable some way from the DIN connector, and take a tap from it.  Having not yet received my 7-pin DIN plug from E-bay, I couldn't wait and just fashioned a 'pin' from 1mm copper wire.

It got me going.  I replaced the wire with a proper DIN plug later.

This is my schematic for the connections:

Et, voila!  Works a dream!

First 24hr reception reports, with a fair few QSOs, too!