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Re: [Amps] SB220 step start blows fuses

Subject: Re: [Amps] SB220 step start blows fuses
From: gudguyham--- via Amps <>
Date: Fri, 7 Jul 2017 14:58:00 -0400
List-post: <>
I know I sound like a broken record but yes, a Variac is the way to go.  
Especially with amps that can have power supply problems and gassy tubes.  You 
will hear the plate transformer groan and won't see HV climbing on the meter if 
there is a problem in the PS long before the smoke Genie appears.  My Variac 
gets used daily several times after doing ANY work on an amp.  It's saved me 
loads of time fixing blown parts that would normally occur if I had just turned 
an amp on with problems.  Best investment I ever made.  0-250 volts at 20 amps. 

Sent from AOL Mobile Mail

-----Original Message-----
From: Bill Turner <>
To: Amps group <>
Sent: Fri, Jul 7, 2017 12:34 PM
Subject: Re: [Amps] SB220 step start blows fuses

------------ ORIGINAL MESSAGE ------------(may be snipped)

On Fri, 7 Jul 2017 10:21:36 -0400, Mark B. wrote:

>A variac varies voltage.   It is not designed to limit current. 


At the very low end of its range, a Variac limits current just fine. I
worked as a calibration technician at Tektronix for years, taking
brand new scopes off the assembly line and powering them up for the
first time. Believe me, a Variac is the only way to go with a unit
which could have any number of problems at first. Over the years I
powered up literally thousands of scopes this way and never a problem
with current limiting. 

73, Bill W6WRT
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