> Date: Wed, 21 Mar 2007 12:32:17 -0400
> From: "Tom W8JI" <w8ji@w8ji.com>
> Subject: Re: [Amps] Surge resistor
> To: "Rick Stealey" <rstealey@hotmail.com>, <amps@contesting.com>
> Message-ID: <01b501c76bd6$92767a80$640fa8c0@radioroom>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
>
> Now you have a .6 ohm resistor that we already know is useless because of arc
> path length) in series with the 50 ohm. All it does is add something to be a
> nuisance later on. It doesn't really protect or fuse anything, it's just
> something to replace later that really never helps.
>
> Why add a part that does nothing?
>
>
>> can't see the value of the 50 watter. In case of
>> extremely high plate
>> current, such as hitting it with full drive and no load,
>> say 2 amps of plate
>> current flows and even then the big resistor only drops
>> 100 volts, and heats
>> up 200 watts. I wouldn't expect a wirewound power resistor
>> to fail
>> immediately under these circumstances, and I can't see how
>> it is protecting
>> anything.
>> What am I missing here? Is the 50 watter the wrong type?
>>
>
> It's for fault limiting. For plate current protection you
> need a real fuse.
>
> 73 Tom
>
>
I have an L-4B and L-7. Both have the same HV supply which uses a 2-watt .82
ohm "fuse" resistor in series in the B+ line. I have often wondered why Drake
did this rather than use a real fuse though the primary side of the transformer
has breakers. There are 2 50K ohm 50-watt bleeders across the output but no
"glitch" resistor. The bleeders cause the supply, which is outboard from the RF
deck, to run hot to the touch.
73, Garry - WR4R
>
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