On Mon, 1 Mar 2010, kernkampj wrote:
Recently I had a problem with a Mitrek radio, The RX channel element
would not reliably start oscillating on power-up. In my
experimenting, I discovered that the problem related to the power
supply I used.
I had four power sources - two linear supplies, one switcher, and a
battery. One of the linears and the battery worked fine. The other
linear and the switcher created the non-start problem.
I finally noticed that the radio has two internal power sources for
the channel element (9.5 Reg and 9.5 switched), and wondered if the
timing of the two sources could be the problem. So I slowed down the
9.5 switched source, and that cured it. The channel element now
starts every time from any of the power supplies.
For those interested, I added a 100uF cap from the base of Q1 (the
receiver 9.5V Switched supply) to ground. This slowed down the
voltage output of the 9.5 switched source.
You might have one or more electrolytic capacitors which have dried out.
I think the last Mitrek rolled off the line before I was born, which is
longer ago than I'd like to admit.
--
Kris Kirby, KE4AHR
Disinformation Analyst
