From: patriot121@msn.com
To: aa6dx@arrl.net
Subject: RE: [Amps] Discharging B+ to ground --
Date: Mon, 23 Nov 2009 16:23:27 -0800
Probably the reason why my Yokogwa P9306UL only shows 200ma at 1KW !!!! I
should fix that.
KC7NOA
>
>
> In regards to discharging the HV caps -- I never knew/thought about this
> before. I have always used a "stick", in commercial amps, or a screwdriver
> shaft that is grounded first to the chassis near the base of the tube, then
> touch the plate connection. Hmmmm ... this sure makes sense -- Thank You,
> Bill! 73 - Mark AA6DX
> ------------
> >>> In a conventional GG amp, both B+ and B- are floating with respect to
> >>> ground,
> >>> except for the connection from B- to ground for the grid current meter.
> >>>
> >>> If the B+ arcs to ground anywhere and there is no clamping diode, the B-
> >>> in
> >>> instantly driven to the full negative HV with respect to ground. If your
> >>> HV is
> >>> 3000 VDC, the B- ;lead becomes -3000 VDC. The clamping diode from B- to
> >>> ground
> >>> prevents this.
> >>>
> >>> Incidentally, this is why one should never short the B+ to ground when
> >>> trying to
> >>> be sure the HV caps are discharged before working on the amp. Short B+
> >>> directly
> >>> to B- only, not to the chassis.
> >>>
> >>> 73, Bill W6WRT
>
>
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