At 09:39 PM 01/17/08, you wrote: >Let me clarify a little bit........ > >I am using the supply to power the Micor repeater as well as a GM300 >link transceiver. A few weeks ago I started to notice a slight hum >on the link radio's transmitted signal. Now, the hum is so bad, and >voltage drop significant, that the GM300's transmit signal is dirty >and sounds like a spurious emitter when transmitting. If I disable >the main repeater TX (Micor), so as to lessen the load and only have >the GM300 transmitting, the hum goes away. Being the GM300 only uses >the 13.8v output, I'm guessing the other outputs are ok. > >I forgot to mention - When I stopped at the site the other day, I >heard the transformer buzzing, which increased in loudness when the >repeater was keyed (thus placing a heavier load on the >transformer). Possible transformer or resonant circuit capacitor >failure? > >I will be stopping at the site in the morning to investigate further >and swap it out with a spare. I'll report back with my findings >later tomorrow. > >Thanks >Eric >KE2D > > > > > >--- In [email protected], Eric Grabowski ><[EMAIL PROTECTED]> wrote: > > > > While I don't have experience with that particular > > power supply, the situation you describe is > > symptomatic of filter capacitor failure. > > > > The capacitor's equivalent series resistance (ESR) > > becomes so high that it doesn't filter the ac ripple > > anymore. > > > > You should be able to verify this easily by using a > > scope to observe the ac ripple on the dc output under > > various load conditions. > > > > Eric KH6CQ > > > > --- kk2ed <[EMAIL PROTECTED]> wrote: > > > > > 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
I'll bet it's the resonant capacitor, but as long as you are in there you will want to look at every electrolytic. Mike WA6ILQ
