Surge limiter. usually installed in one leg of the AC line connection.
When cold, have high resistance. When hot, low resistance. So, they run warm
to hot when in use. You would not want them to be located in a stream of
cooling air as that could spoil the low R characteristic.
Very interesting and useful device. I use them to limit turn on filament
current in large transmitting tubes.
Available through Mouser and other distributors.
73,
Gerald K5GW
In a message dated 2/13/2014 10:15:13 A.M. Pacific Standard Time,
bcarling@cfl.rr.com writes:
The little black varistor thingies work quite nicely for eliminating that
"THUMMMPP!" in small to medium-size equipment.
I don't really know what they are but somebody gave me a whole bunch of
them a while back. I have two or three different sizes.
Best regards - Bry Carling
> On Feb 13, 2014, at 10:08 AM, Jim W7RY <w7ry@centurytel.net> wrote:
>
> That's why I put step start in my large Astron power supplies. No more
thump. No more blown up power switches.
>
> 73
> Jim W7RY
>
>> On 2/13/2014 4:01 AM, Ken Durand wrote:
>> " And this, my dear friends, is why equipment with steel boxes and big
>> transformers inside can make that "WHummpppp" at the moment it's
switched
>> on.
>>
>> Of course, in equipment controlled by a simple mechanical power switch,
it's
>> impossible to decide when exactly in the cycle the switch will close.
It's
>> this a lottery how close we will get to the peak voltage point, or the
zero
>> crossing. That's why sometimes the "WHummpppp" is strong, sometimes
weaker,
>> and sometimes even non-existent."
>>
>> Thanks for that bit of wisdom Manfred. I never could figure out why
>> sometimes I get the "WHummpppp" and other times the sound would be quite
>> different or non-existent like you described.
>>
>> Ken
>> N4zed
>>
>> -----Original Message-----
>> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Manfred
>> Mornhinweg
>> Sent: Wednesday, February 12, 2014 12:56 PM
>> To: amps@contesting.com
>> Subject: Re: [Amps] Solid state relays..again
>>
>> Hello,
>>
>>> Once in a while that thing turns on with a WHummpppp and a low
>>> frequency ringing that just trails off.
>> Let's see if I can explain this in a way everyone can understand.
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