Eric, Without knowing what model of power supply you have, my first guess is that you have an open diode in the high-current supply. An open diode will cause low voltage, high ripple, and major hum. However, your comment suggests a gradual onset of hum, which may indicate a filter capacitor failure. If your power supply has a ferro-resonant transformer, you may have a bad commutating capacitor. Not enough info to make this call...
Do you have the manual for your specific power supply? If not, what model power supply is it? 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of kk2ed Sent: Thursday, January 17, 2008 7:59 PM To: [email protected] Subject: [Repeater-Builder] Micor power supply issue Good Evening, I have a Micor 75 station power supply that is acting up. When the repeater is idle, the voltage output appears clean. But as the load is increased (ie: power output increased), the voltage sags and I get an annoying hum on the tx (indicative of AC ripple on the dc side?). It started out as a barely noticeable hum; the past few days it has gotten to the point where I just shut down the repeater's tx. I haven't had a chance to get to the site to swap it out with a spare. But I'm curious as to what kind of repair I'm in for, and others' experience with Micor supplies. What tends to be the failure and/or cause of the above condition? Pass transistor failure? Filter caps? Ferro-resonant circuit (cap)? Thanks for any input Eric KE2D
