[ICOM] icom 706 MK2

[Facility 406]

> This is the best place to test. Measuring current at two places in a 
> series circuit is of little benefit, as the current must be the same, 
> following accepted electrical theory.

I would guess, in a perfect conductor with no breaks or changes.

Due to the numerous bad connections within the cable, current can change 
at each one, due to heating, corrosion, arcing, loose connections, bad 
alloys, bad plating, fuse issues, insulation in crimps, broken/missing 
wire strands, et cetera.

There would be a total draw, but current at the fuse input, for example, 
may be a few amps, and with six failure points per fuse/clip alone, per 
side, may only be providing a few hundred mA down the cable to the 
radio, and, with entirely different issues between +, and -.  3A draw at 
the supply doesn't mean the radio is getting the roughly 3A it's known 
to require at idle.

The corroded, arcing, loose, charred power connector may be drawing 3-4A 
from the supply, and providing barely enough power for the 706 series 
"relay click", or worse, chattering, which is always scary for a radio 
turned off, and not being touched, and no change between a good power 
supply, and fully charged battery.

"Hmm....  Must be something in the radio, it's getting power, and 
drawing a few amps, but it makes funny noises, and won't turn on.  Power 
supply checks good with other equipment, 13.8V even at 20-30A, yeah, 
must be the radio!"

I've had areas within the factory cord be so bad, the relay click is 
heard when applying power, but the radio cuts out just trying to turn 
on.  If/when it does turn on, various failures, at various powers, 
depending on how the power cable was handled between uses, or the extent 
of failure conditions occurring during previous use and storage.  But, 
in the end, yes, a total current, indicating something is happening, but 
not what, where, how, to what extent, or, if equal, reasonable, or expected.

Sometimes the issues were easy to find.  Charred metal, faint hissing 
from arcing, hot spots, the loud snap of a cracking fuse from excess 
heat due to bad clips, or poor fuse element connections at the caps, hot 
insulation smells, burning metal smells, or wires falling out of crimps

Testing the radio internally could be interesting, but drawing out the 
cable, fuses, and connector, I get 16 known, and 2 more potential 
failure points, before the power cord is even connected to the radio. 
Once connected, most were known to occur, sometimes several at once.

The cables were known bad, new, out of the box, seriously, just outright 
trash, and got worse with actual use, both mechanically, and 
electrically.  It was a big deal at the time, lots of posts in the 
forums about it.  I had to change everything from the PCB inside, to the 
power supply just to use my radio when new, the cable was erratic in a 
mostly static desktop installation, and completely useless when mobile. 
  Ten, twenty, or more, years of use and abuse later, assume far, far 
worse, than, known bad, out of the box.

Aside from a common trace corrosion issue due to a rubber pad with high 
acid content resting on the main PCB, or exceptionally filthy user 
conditions where the faceplate/head connections get covered in scum, 
causing erratic operation, or failure to turn on, I don't recall having 
heard of an actual radio issue, other than comments of a very warm 
regulator in the head or a sluggish screen at very cold temperatures.

Kurt