[K3] Overvoltage protection?

[Dan in Florida]

I recently purchased a 35 amp Astron power supply at a hamfest (in great condition).  Upon inspection, I found that the crowbar SCR had failed, and had been removed.

Although I've replaced the SCR, I'm wondering if the K3 has overvoltage protection of some kind?

As an aside, I would like to test the crowbar circuit in the Astron, but with that big capacitor in there, I'm kind of hesitant.  That big capacitor would have to discharge before the primary fuse would blow (maybe blowing the SCR)--right?  I'm thinking of putting a 25 amp fuse in series with the capacitor.  Anyone address this before?

Thanks,
Dan - W4TQ
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[Tom Hammond-2]

Dan:

If the Astron is working AS INTENDED, when the OVP SCR fires, the UA723 VReg
will immediately go into over-current protect mode, reducing the output current
to <1A WITHOUT damaging ANYTHING!  Same as if you placed a short directly
across the output terminals of the supply.

The ONLY time the fuse should blow is if the p ass transistors shorted.

73,

Tom Hammond   N0SS

At 20:28 02/28/2010, you wrote:

>I recently purchased a 35 amp Astron power supply at a hamfest (in
>great condition).  Upon inspection, I found that the crowbar SCR had
>failed, and had been removed.
>
>Although I've replaced the SCR, I'm wondering if the K3 has
>overvoltage protection of some kind?
>
>As an aside, I would like to test the crowbar circuit in the Astron,
>but with that big capacitor in there, I'm kind of hesitant.  That
>big capacitor would have to discharge before the primary fuse would
>blow (maybe blowing the SCR)--right?  I'm thinking of putting a 25
>amp fuse in series with the capacitor.  Anyone address this before?
>
>Thanks,
>Dan - W4TQ
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html

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[Hardy Landskov]

To all on the net:
I bought an AS35A at a swap meet and so far it's doing it's thing just fine
with the K3.  But there was no paper work. Are there tests I can do that say
yeh verily this thing works as designed?
73 N7RT

----- Original Message -----
From: "Tom Hammond" <[hidden email]>
To: "Dan & Jean" <[hidden email]>; <[hidden email]>
Sent: Sunday, February 28, 2010 7:35 PM
Subject: Re: [Elecraft] [K3] Overvoltage protection?

> Dan:
>
> If the Astron is working AS INTENDED, when the OVP SCR fires, the UA723
> VReg
> will immediately go into over-current protect mode, reducing the output
> current
> to <1A WITHOUT damaging ANYTHING!  Same as if you placed a short directly
> across the output terminals of the supply.
>
> The ONLY time the fuse should blow is if the p ass transistors shorted.
>
> 73,
>
> Tom Hammond   N0SS
>
> At 20:28 02/28/2010, you wrote:
>>I recently purchased a 35 amp Astron power supply at a hamfest (in
>>great condition).  Upon inspection, I found that the crowbar SCR had
>>failed, and had been removed.
>>
>>Although I've replaced the SCR, I'm wondering if the K3 has
>>overvoltage protection of some kind?
>>
>>As an aside, I would like to test the crowbar circuit in the Astron,
>>but with that big capacitor in there, I'm kind of hesitant.  That
>>big capacitor would have to discharge before the primary fuse would
>>blow (maybe blowing the SCR)--right?  I'm thinking of putting a 25
>>amp fuse in series with the capacitor.  Anyone address this before?
>>
>>Thanks,
>>Dan - W4TQ
>>______________________________________________________________
>>Elecraft mailing list
>>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>Help: http://mailman.qth.net/mmfaq.htm
>>Post: mailto:[hidden email]
>>
>>This list hosted by: http://www.qsl.net
>>Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html 

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