From: "Gerry" 
Subject: RE: [drakelist] AC-4 Cap values

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Unfortunately, inserting series =
resistors
in the B+ leads will, depending on the value, adversely affect =
regulation. It may
work fine for static loads such as the +250 supply but is not advisable =
for HV
supplies with dynamic loads. Years ago I tried a home brew power supply
constructed with mil surplus components. What I found is that choke =
input
supplies need a critical value resistive load to maintain the voltage =
below
allowable limits. With no load on the +650 volts, it went almost to the =
rating
of the filter caps which I believe was 800 volts. Trying another =
approach with
a capacitive input filter and a choke meant I had to find another =
transformer.
When I did, the 50 Ohms resistance of the choke became somewhat of a =
problem
which all made sense later. At 450 mils, that would be a 22.5 volt drop =
on top
of whatever the drop was in the first place. The thump comes from the
transformer and is loudest when power is switched on at the peak of the =
primary
AC cycle. Sometimes you can hit it just right. When I built my Heathkit =
SB-1000
linear, there was an alignment procedure which called for removing the =
screws
and sliding the case back about an inch or so. This was done per the =
assembly
instructions to align the input coils. When I turned on the amp for the =
first
time, there was a loud KABAM! After changing my underwear, it became =
obvious
what happened: there was a surge at turn on and the steel cover acted =
like a
sounding board. Nothing bad happened to the amp, it was just one of =
those
things that makes you tremble whenever you reach for the ON switch. This =
brings
up another point about the need for slow-start on such devices. I =
don’t
use the linear often but it is on my to-do list.

 

-----Original =
Message-----
From:
owner-drakelist{at}www.zerobeat.net =
[mailto:owner-drakelist{at}www.zerobeat.net] On Behalf Of
k5vkl{at}juno.com
Sent: Thursday, March
03, =
2005
2:54 AM
To: =
drakelist{at}www.zerobeat.net
Subject: Re:
[drakelist] =
AC-4 Cap
values

 



Carl,





 





Now might be a good time to review some =
slow-start
feature design reviews,





looking forward to incorporating one into the =
turn-on
function of the power





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