Sb-301

[Dan Merrick]

Chris:

I'm just talking about High Voltage supplies in
general and not specific to a particular piece of
equipment. If the HV Secondary winding uses a grounded
center tap to provide a return for a full wave
rectifier circuit, the fuse may be placed between the
center tap and ground. Then a 3AG fuse should suffice.
You could also put a standby switch in series with the
fuse to ground if the circuit is not equipped with
one.
73,  Dan Merrick -- K8TX

Don't know about the quick and easy but one thing you
will have to 
watch 
is the type of fuse you use if on the HV secondary.
The normal 3AG 
glass 
fuses are only rated for a (?) 125 VAC. There are
ceramic cased 
versions 
which I think were intended for higher voltage
service. To set  the 
fuse 
rating, you would want to:
1.    Find out the maximum RMS current that you will
be pulling
2.    Look on the Internet or some othe source for
some manufacturer's 
data sheets and, most particularily, the current/time
curves.  Then you 
find a fuse which will 'hold' the current you want for
infinite time 
with some safety fudge (say 50%) but not too much!

The light bulb - hummm.  Don't know about that.  Same
problem with 
voltage rating.

73
Bob, WA2CKY

Chris Campbell wrote:

> Bob And Bettina Groh wrote:
>
>> Chris,
>>
>>   Hopefully the 'smoke' is from an overheated (and
failed) 
>> electrolytic and not a nuked power transformer
(which failed because 
>> of a bad electrolytic). If the former, you should
be able to replace 
>> the cap(s) [more later] - if the latter, you are
probably left with 
a 
>> parts rig as power transformers are hard to find.
>>
>>
> This is a question from a different Chris.  I recall
reading 
somewhere 
> about fusing the HV secondary of  power transformers
on tube 
> equipment, to protect against filter capacitor
failure.  There must 
be 
> some quick'n'easy way to calculate the size of the
fuse for various 
> applications, but for some reason I'm drawing a
mental blank right 
now.
>
> I also recall seeing somebody suggest placing a
standard small lamp 
on 
> the CT of the secondary, to serve as a fuse.
> Does anybody have suggestions for either one?
>
> Chris Campbell

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