[AMPS] Noise above 50/60Hz

[km1h@juno.com]

On Wed, 28 May 1997 12:14:37 -0700 (PDT) Skip <mays@indigo.ucdavis.edu>
writes:

>
>Yes and no Carl,
>I don't consider it an exclusive DC portion of the power supply, 
>although 
>I get your point.
>
>Line filters are a wonderfull way to prevent problems, Mov's are nice 
>but don't save the day every time.

I agree Skip about the alternatives. 
 It is a problem here with my response time since my JUNO mail provider
is a batch mode operation PLUS I only check once a day or so. My replies
may be a day  or more out of date at times!


 A spike on the power line will pop 
>open or short an MOV, (I've seen both) and the next spike will take 
>out 
>the circuit if the MOV opened. This is not exclusive circuit 
>operation, 
>just some of the many horror stories I've seen close up. All dependant 
>on 
>the design of the power supply of course. Properly done, a shorted MOV 
>
>would trip off a power supply, but some circuits need to "recycle" and 
>
>stay in operation, trying to prevent damage as possible. 


I believe that Ian covered MOV's better than any published version I have
read. His "memory" comments really hit home here since I have experienced
a high incidence of MOV failures....all GE and not floor sweepings
either.  Maybe the hilltop and its lightning attraction has a "bit" to do
with it.   


>Broadcast transmitters and Generation control circuits are a great 
>example.
>A lightning storm in the Sierra Nevada is an exciting place to "watch" 
>>the grid from a generator control room.
>The frequency responce of the Transformer plays an important role in 
>my 
>designs.  I measured the responce of a Heathkit SB-220 fillament 
>transformer years ago and found that it's design was especially good 
>for 
>inrush current limiting and a relatively low Fc. 


The SB-220 filament xfmr was DESIGNED for low in-rush current. Anyone
modifying that circuit is wasting time and money.  



>I'm not sure if the designers of the amp or the transformer planned it 
>that way, but the transformer prevented more than one problem "out of 
>the box".

See above...yes they did.


 I do wish I knew who made the originals for Heath?

How many do you want?? No I did not provide the originals but the design
is no secret. I design/build/sell transformers up to 20KVA. 

 
>The point I'm trying to make is that High frequency components do make 
>it 
>into the "DC" portion of a HV ps and that properly chosen bypass caps 
>would seem to prevent more problems than they would cause.

We disagree here Skip. My input is that randomly selected caps can
actually generate a problem......sort of LF parasitics I am told.  Don is
away in your area this week but I will ask him when he returns. My input
from him is that NO caps are the way to go...the diode does all the work
required.  

>Please have your friend advise us why we might not want these 
>capacitors 
>in circuit. I'm always open to other opinions and ideas.
>thanks for your thoughts
>
>73's
>Skip May  wv6f


73....Carl   KM1H

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