[Amps] B- questions

[Doug Renwick]

In the Ameritron AL-1500 are you referring to diode D16, 1N4007 on the
filter capacitor board?

Doug

I'll run the race and I will never be the same again. 

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]
On Behalf Of Bill, W6WRT
Sent: November 8, 2009 9:02 PM
To: amps at contesting.com
Subject: Re: [Amps] B- questions

ORIGINAL MESSAGE:

On Sun, 8 Nov 2009 18:43:18 -0500, "Carl" <km1h at jeremy.mv.com> wrote:

>
>I'll repeat one more time. The dinky diode doesn't prevent tube and
circuit 
>damage, it shorts after the damage is done. 

REPLY:

You are half right.

I agree it won't prevent tube damage, but it will indeed prevent damage
caused
by the B- line being driven to the full HV negative with respect to
ground.

Think about a negative 3000 volt pulse being coupled back through the
input
circuit to the output of your transceiver. Think about a negative 3000
volt
pulse appearing on the cathode of your tube if the filament is DC
grounded. If
the filament is connected to the cathode, think about a 3000 volt pulse
applied
to the secondary winding of the filament transformer. Think about the
tube
socket, the tuning caps in the input circuit, etc, etc...   Few if any
of those
components will withstand the full HV.  Get the idea?

Thank goodness for the dinky diode!     :-)

73, Bill W6WRT