[Top] [All Lists]

[Amps] SB220 step start blows fuses

To: <>
Subject: [Amps] SB220 step start blows fuses
From: "Jim Thomson" <>
Date: Fri, 7 Jul 2017 09:23:06 -0700
List-post: <>
Date: Fri, 7 Jul 2017 01:07:36 +0000
From: Bill Turner <>
To: Amps group <>
Subject: Re: [Amps] SB220 step start blows fuses

<Because of all the above, IMO, a better way is to use a Variac to
<slowly bring up the voltage while monitoring the current. Variacs are
<widely available on eBay. Every ham shack should have one. 

<73, Bill W6WRT

### be careful with any variac rating.  The small  0-120 vac  or 0-132
1.2 amp types, typ 3 inch diam x 2 inches thick, are only rated at  157 va..and 
based on 132 v  X  1.2 A.   The tubes alone will suck  150 VA.  If careful, you 
test the HV portion of the supply, with tubes removed.

##  To use the varaic,  you really need a 5A  or larger variac,  if using a 
0-120 or 0-132
V type.   You also need to temp disconnect the entire step start assy..and feed 
the output 
of the variac directly into the 120 vac input of the plate xfmr.   IF the step 
start assy is included
in the mix, and low voltage on the varaics output....step start relay will not 
pull in, and step start
resistor is still in the circuit, and you will probably end up with a blown 
step start fuse. 

##  with step step assy temp out of the circuit.....and  starting with the 
variac on zero,  + a safety 
fuse on the input of the variac, + both either both tubes  removed from 
sockets, or anode leads
temp dis connected... then bring the variac up real slow.   If u have any fubar 
in there, the small 
1-3 A safety fuse on the input of the variac  will open up.   Removing tubes 
from sockets will eliminate 
the 150 va fil load. 

##  If fuse blows open, disconnect the 8 filter caps + doubler diode 
board...leaving just the xfmr, with 
nothing connected to sec of plate xfmr.  Try again, if good,  add in the 
doubler diodes, then re-test, then
evaluate.  If good, add in the 8 x caps, then re-evaluate.   Its really just a 
simple process of elimination. 

##  Once the B+ supply is working correctly... ok,   remove variac,  add the 
step start assy to the mix...then evaluate. 
If good, then install both at a time. 

Jim   VE7RF

Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>