[Amps] Amps Digest, Vol 93, Issue 16

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Sun, 12 Sep 2010 08:31:32 +0100, Ian White GM3SEK
<gm3sek at ifwtech.co.uk> wrote:

>SHV connectors have been very carefully designed with deeply recessed 
>pins on both male and female. If they are hot plugged, the connector 
>bodies will make a good ground connection *before* the HV contacts come 
>together. Likewise when unplugged, the HV connection is broken before 
>the ground connection.

REPLY:

I am not familiar with SHV connectors other than what I read in
Wikipedia, so I'll take your word for it. I remain highly suspicious
of coax braid being used in a safety situation, however. My experience
with coax braid over the yearsis that it is prone to breakage at the
point where it contacts the connector shell, regardless of what type
of connector is used. Perhaps the SHV is better than others in this
regard. 

However, I stand by my recomendation to have a separate, solid ground
connection between the amp and PS chassis, entirely indepencent of the
HV conector. This gound wire should be connected at both ends with a
nut and bolt or screw, not a slip-on connector. It should be the first
wire connected and the last wire removed when working on the units.
This will help reduce shock hazard from an AC line fault as well as HV
issues. 

Likewise, the B- wire should be protected with a pair of heavy duty
diodes, in reverse parallel INSUDE THE PS (not inside the amp) to
prevent the B- lead from going to full negative HV in case the B+ arcs
to chassis. If one wants to install a second pair inside the amp for
grid meter protection that's fine, but the pair inside the PS is a
must. 

Bill, W6WRT