Keep in mind that most of the over voltage protection circuits that use a SCR on the output (Astron) require you to turn off the supply to reset the protection. Not a good thing for a remote repeater if you have a spike that simply triggers the SCR. Astron has another circuit option that corrects this problem.
Gran K6RIF At 09:51 AM 1/17/2007, you wrote:
Bob sed: > > A long time ago I happened to find a crowbar "bar" made by Lambda > > at the local TRW swap meet. I added it to a supply without > built-in > > OVP to add said protection to the equipment. I have some of those in a box somewhere if anyone is looking for any. Some are adjustable voltage, some are fixed. Skipp sed: > Astron designed their crowbar circuit to short the supply output. > The shorted output protects the user equipment and tries to > force the AC Mains fuse to open through excessive transformer > primary current draw. If the regulator is working right, it will go into current limiting, rather than blowing the fuse. This is typically what you find when you get to the site to figure out why your Astron-powered repeater isn't working... > The bad news is found when modest size power supply - ac mains > fuses are replaced with excessive large current values (the trusty > 25 or 30 amp 3ag fuse everyone seems to have a lot of...). Maybe they think they need to go that big to handle the inrush current? A properly-sized fuse should be able to handle the inrush current without blowing (even if it's not slo-blo). However, I can't say the same for circuit breakers in the panel. Don't know how many times I've tripped a 20A panel breaker by turning a 50A Astron on... --- Jeff
