[Johnson] PTT Keyer line HV Cautions

[John Lawson]

On Thu, 16 Feb 2006, Dee C. Almquist wrote:

> Dear Ranger Ops

>  The object of this mod is to eliminate the complication & HI
> VOLTAGE on the key line.

   An Unnamed Friend of mine just destroyed a vintage audio compressor because 
the PTT and Mic wires got reversed in one of a chain of several XLR connectors.

   168 Volts on the output jack of an IC-based device is slightly out of 
spec, and did just what you'd think it might.

   Luckily - there's no physical damage, ie blown traces, etc.  But there 
are a few opamps that have lost their Magic Smoke. Several new small 
containers of Smoke are on the way, to be soldered in and pressure-tested.


   In my set-up, I've run everything external to the Valiant and Rangers (and 
Elmac) on 24VDC plug-in relays (because I had a drawer full of 'em) and thus no 
HV gets out onto the Control and Audio chains. This includes the 120VAC for the 
Dow-Key TR relays.

   There are a few really DUMB things Johnson did - the microphone connector 
arrangement is, IMHO one of them.


   Cheers

John  KB6SCO