Hi, Bob. Long time, no chat! The Astron P/S only supplies the PA - all other items in the rack have their own power supplies, but I can still see where I may have exceeded the MICOR supply current limits.
Other than that, I've been told to check al the coax jumpers to ensure they are in good order... to eliminate any RF issues. I do access to a 120A switcher that I may try and see what happens. Mark - N9WYS -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, December 08, 2008 9:54 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Astron P/S question I've had DMMs also go nuts at my site too. Luckily the Astron supply hasn't had that problem yet. The fuse usually blows when something catastrophic happens. One such thing is when the output voltage goes too high and the built-in SCR crowbar fires. It shorts the supply immediately, and the excess current usually causes the fuse to blow. Sometimes it also causes the diodes to short out, and they end up blowing the fuse. RF getting back into the supply can trip the SCR. Even RF riding on the supply lines can cause the voltage that the SCR sees to be high enough to trip it, even though it may not show up with a meter or even a scope. You've probably done all you can with the ferrites unless you missed the wires going to the SCR. On some supplies it's mounted to the chassis and has fairly long wires (just waiting to pick up RF) running to it. You'd be better off with ANY kind of unregulated power supply, such as what you had with the MICOR supply. Ferro-resonant transformers usually aren't susceptible to such RF problems, and there's nothing electronic such as a crowbar inside to trip and blow the fuse. This doesn't explain why your MICOR supply blew its fuse, unless you exceeded the output current capability. Most MICORs were only rated up to 100 watts, and the supplies probably are good to 25-30 amps MAX; it seems that your PA is already exceeding that. Then you tack on a receiver, exciter, etc, and you've gone past the limit for the MICOR supply. Even an MSF5000 supply would be strained to handle that much current; that's why the bigger stations have TWO supplies, one for each PA, and the VHF stations have 28V supplies in them. Solutions? You might consider a battery and a charger that's strong enough to keep the PA happy, to run just the PA. Split everything else off and run that on another smaller supply. Consider a switching regulator supply, rather than a linear regulator supply, to run the rest of the equipment. I know that some of the high power amps are now being built to run on 24-28VDC. This cuts the current consumption in half and they can be run with switching supplies. Let's hope Skip comes aboard here. I know he's had experience with these units. Bob M. ======
