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Re: [TenTec] Need advice about OVP for 262G

To: tentec@contesting.com
Subject: Re: [TenTec] Need advice about OVP for 262G
From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Reply-to: geraldj@storm.weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Wed, 01 Apr 2009 10:18:27 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
On Wed, 2009-04-01 at 08:56 -0500, Hulett, Russell wrote:
> Hello Mike,
> As I read the datasheet for the 1.5KE15A, the breakdown voltage is nominally 
> 15 VDC.  So when the pass transistor shorts, won't the transient diode limit 
> the voltage to the load to nominal 15 VDC, bypassing enough current to ground 
> to trip the overload on the power supply?

Nominal at a particular current. Higher current from the supply the
voltage is higher, maybe a lot higher.

> I intend to incorporate a fast-blow fuse, not sure why the question prompted 
> the sarcasm.

Until you get to the super fast silver element fuses, a fast blow fuse
is just a good indicator that the associated transistor has melted. E.g.
the lifetime of the overloaded semiconductor is shorter than the fuse.
> 73, Curt KB5JO

Then the added voltage drop of the fuse and fuse holder take away from
the desired power supply regulation.

73, Jerry, K0CQ

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