Many resistor types will explode when that much energy is dumped into them
from a tube "glitch". One reliable type is an Ohmite "Brown devil" I use a
Ohmite BD of 25 Ohms at 25W in my SB-1000. I used this amp for checking a
large batch of
3-500Z with a number of them breaking down. All I had to do was to reset
the circuit breaker.
John
KU6X
Today's Topics:
1. SB 220 Exploding Resistor (Tom Hellem)
----------------------------------------------------------------------
Message: 1
Date: Sun, 17 Jan 2016 09:05:58 -0700
From: Tom Hellem <tom.hellem@gmail.com>
To: Amps@contesting.com
Subject: [Amps] SB 220 Exploding Resistor
Message-ID:
<CANyX0AqkKbdWNTusW-GRD_6kVZpiC1ZnE7u2ed6V2J5A_zjG3g@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Hi-
My SB 220 has what appears to be a glass coated wirewound resistor in
series with the anode B+
supply lead just before the RF chokes. It is not on the schematic so must
have been a modification
done at some point. It blew up in spectacular fashion one day and I
hesitate to just replace it without
having some idea of what may have been the root cause. I do not have much
of an electronics background
and would appreciate if someone could suggest some things that I should
check out before I try to put it
back on line.
73 To All on The List.
Tom
K0SN
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Message: 4
Date: Sun, 17 Jan 2016 19:56:19 +0200
From: Vic Rosenthal <k2vco.vic@gmail.com>
To: Tom Hellem <tom.hellem@gmail.com>
Cc: Amps@contesting.com
Subject: Re: [Amps] SB 220 Exploding Resistor
Message-ID: <29B8FA5F-D4F7-45C0-A734-1D14771CEC0C@gmail.com>
Content-Type: text/plain; charset=us-ascii
This is a 'glitch resistor' intended to protect tubes and other components
against arcs caused by gassy tubes. You might replace it with a 25 or 50 ohm
50w resistor and it will work fine, if the tubes survived the arc that blew
it up. I have seen this happen with no apparent ill effects. On the other
hand, a tube might be gassy and arc again, or the grid may have been damaged
by the arc. Check the components connected between the grids and ground;
they are often damaged by plate-Gris arcs.
Vic 4X6GP/K2VCO
> On 17 Jan 2016, at 6:05 PM, Tom Hellem <tom.hellem@gmail.com> wrote:
>
> Hi-
> My SB 220 has what appears to be a glass coated wirewound resistor in
> series with the anode B+
> supply lead just before the RF chokes. It is not on the schematic so must
> have been a modification
> done at some point. It blew up in spectacular fashion one day and I
> hesitate to just replace it without
> having some idea of what may have been the root cause. I do not have much
> of an electronics background
> and would appreciate if someone could suggest some things that I should
> check out before I try to put it
> back on line.
>
> 73 To All on The List.
>
> Tom
> K0SN
> _______________________________________________
------------------------------
----- Original Message -----
From: "Steve Flood" <kk7uv@bresnan.net>
To: <amps@contesting.com>
Sent: Sunday, January 17, 2016 8:36 AM
Subject: Re: [Amps] Need for bias switch (CW/SSB)
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