[Amps] SB-220 6M conversion

Jim Thomson jim.thom at telus.net
Sat Jun 6 13:24:03 EDT 2020

Date: Sat, 6 Jun 2020 09:28:30 -0400
From: Artek Manuals <Manuals at ArtekManuals.com>
To: n2ic at arrl.net, "Amps at Contesting.com" <amps at contesting.com>
Subject: Re: [Amps] SB-220 6M conversion

<Running in the CW position just to be on the safe side ( after all this 
<amp is nearly 40 years old) Going easy on the power transformer. I can 
<only get about 100 more watts in SSB position


##  One other  note.  If  you want a fast grid fuse, for a hard  fault,
install a 3AGC  fuse holder on the rear apron.  Then  wire it  between 
chassis  and  bottom end of  grid shunt.  Use a FAST 3agc  fuse, like
a 250-300-400  ma  type. 

##  if  something goes amiss,  like you lose the  B+,  overdrive, arc,
parasitic etc, and grid fuse opens  up,  you will  no  longer  have a 
path  for  DC  grid current.  Tube can no longer  be  driven.  Power
output drops to zero, and  input  swr rises to infinity,  and xcvr  shuts
itself  down.... event  over. 

##  Install a HV fuse in series with the  B+.... followed by a 
50 ohm @  50 watt  wire wound.... or 2 x 25 ohm @  25 watt
wire wounds in series. 

## Then its all protected.

Jim   VE7RF 

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