Yesterday I swapped the PSU module 5 from my 'good' RT-320 into the 'test bed' RT-320, ready to work on this evening. This module was completely rebuilt by David G3RYP using modern DC-DC converter modules.
This left my good radio looking a little vulnerable! So, I placed some liberal 'Do Not Touch' notices about the place to ensure my good lady left well alone!
The picture above (apologies for the poor focus!) shows the uncanned module in situ on the test bed radio chassis. The modern modular construction can be seen.
Tonight, Ive powered the radio up and tested with this module - no fault! So, the issue is definitely in the original PSU module 5. I just have to figure out what!
In the meantime, I finally got around to sorting out my spare handset with a curly cable! I could find no info on this cable, so after metering out all the wires and making a list of which pin goes to which colour wire, against the known use of each pin, I set about working out which terminals in the handset did what.
I managed to get all but one connection made using the press on terminals. Testing as I went, first the PTT pressel, then the loudspeaker audio. The audio output of the RT-320 goes in parallel to both 'channels' so I just chose to use the one with the most conveniently sized wire! The final wire, seen above being tested with a jumper lead, was one of the mic connections. As this was a spade terminal on the mic element, the round connector on the wire was no use. This had to be cut off (retaining enough of the crimp so I could solder to it without having to deal with Litz wire!) and another length of wire added to reach the mic, where it was swiftly soldered to the terminal.
Lots of testing followed, including dealing with the PTT being stuck on if the middle case back screws were tightened up first! But its now working, and will be much more convenient than the straight cable of the other handset for some jobs.
I now have the BAT53 Schottky diodes and the 3.3V regulator modules ordered. Once these arrive I can start modifying the test bed radio ready for trials of remote control. I'll also need to work on making one of the audio ports a data port.