Need to buy a part

[Karl W4KRL]

Mike,

 

Looking at the schematic, I don't see a fuse in the dc side. It looks like
the crowbar has to handle dumping all the capacitor energy and then waiting
for the current to build up in the primary of the transformer until the ac
line fuse blows. Unless I am missing something this is a poor way to
implement a crowbar circuit. You might be able to continue using a similar
sized SCR by adding a quick blow dc fuse between the emitter resistors and
the crowbar.

 

http://www.repeater-builder.com/astron/pdf/astron-rs70a-rs70m-2007-01.pdf

 

Karl W4KRL

 

From: Michael Chisena [mailto:ka2zev at yahoo.com] 
Sent: Tuesday, December 27, 2011 9:49 AM
To: tacos AMRAD
Subject: Need to buy a part

 

Hi all,

Still working on that Astron 70 amp PSU.

Seems the OEM used an 'under sized' SCR as part of the crow bar circuit.

According to the web nobody offers this part, and if they did, it still was
not enough SCR to shut this thing down in the event of a runaway.

 

Anybody have an SCR that is a good drop in for this project? And do you want
to sell it.

 

I am not adverse to drilling new holes in this thing, so if you have a big
stud mount part, that is ok.

 

Here are some 'in process' photos.

 

http://www.flickr.com/photos/90108848@N00/sets/72157628575273797/

 

Thanks

Mike

 

"You are, what you do, when it counts" 
The Masso

"Gravity, the quickest way down" 
Mayor John Almafi

 

"You ever drop an egg, and on the floor you see it break? 
You go and get a mop so you can clean up your mistake. 
But did you ever stop to ponder why we know it's true? 
If you drop a broken egg you will not get an egg that's new?" 
MC Hawking

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