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
>
>
>
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