[Elecraft] K3 Keyout?

[Fred Townsend]

Jack:
A diode is a good idea and sound engineering practice. However if you look
at the FET schematic from the manufacture's data sheet carefully you will
see that the FET has a built in diode.  That's why they make such good relay
drivers.
73
Fred, AE6QL

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jack
Brindle
Sent: Monday, September 7, 2015 7:49 PM
To: Jim Miller
Cc: Elecraft Reflector
Subject: Re: [Elecraft] K3 Keyout?

If it were _my_ K3 (or K3S), I would add the very inexpensive 1N5400 or
1N5407 diode across the relays and eliminate the worry. Even reed relays can
produce quite a kick, and the low cost of the diode would do wonders for
peace of mind.

This same advice goes for antenna (and other) relays switched by the KRC2.

Jack Brindle, W6FB

 
> On Sep 7, 2015, at 5:40 PM, Jim Miller <jim at jtmiller.com> wrote:
> 
> Thanks all. The 200v tolerance will handle the minimal energy produced 
> by the reed relay field collapsing.
> 
> 73
> 
> jim ab3cv
> 
> 
> 
> On Mon, Sep 7, 2015 at 8:32 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
> 
>> Why do you need to look at the schematic.  The K3S specification says 
>> it will handle +200 volts at 5 Amps, so those are the limits at the box
level.
>> No matter what the device data sheet for a device might indicate, 
>> there can be other considerations in the K3S design (or other 
>> 'boxes') that say you should observe the specifications for the 
>> entire unit rather than trying to re-engineer from the device
specifications.
>> 
>> 73,
>> Don W3FPR
>> 
>> 
>> On 9/7/2015 7:59 PM, Jim Miller wrote:
>> 
>>> I don't have schematics for my K3S but going by those for the K3. 
>>> The KeyOut line (RCA Jack) is driven by a IRF1630 which appears to 
>>> be out of production. Either than or it is a misprint and is actually a
IRF630.
>>> 
>>> If the latter it appears pretty burly. Can I assume it can drive a 
>>> pair of reed relays without suffering an inductive kick failure?
>>> 
>>> 
>>> 
>> 
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