Archive of the former Yahoo!Groups mailing list: MOTM

My MOTM-700 was working fine except that it was effecting other
modules through the power supply.

It caused an audible glitch in other modules. This happened whenever a router
switched from one state to the other. This happened even if the 700
was only connected by its power connector. The problem was easily
heard by using a 320 in the audible range. Both routers within the 700 were
identical in effect, and the problem seemed twice as bad when both
routers switched at the same time.

Has anyone reported this or a similar problem?? One could easily be
fooled into thinking that a noise heard when switching audio is
caused by the VCA circuitry. My guess is that there is a transient
from the LED's (perhaps both LED's are lit briefly exceeding the
capacity of either the 12V or 5V regulator).

C1 is a capacitor going to ground between the 5V regulator and LED's.
The one from my kit was a 10uF 50V cap. I didn't have any 50V caps
that would fit, and the schematic shows a 10uF 25V. So in order to
provide more local storage, I put in in a 47uF 25V cap. The problem
went away, but after a couple of minutes the 700 started behaving
erratically, and then stopped working altogether. The cap burned
out. It's now a perfect DC conductor sitting in my trash bin.

So I put in a 47uF 35V cap. I had it running all night, and it is
still working fine. No more PS glitch.

I still have no idea how 5 volts destroyed a 25V cap.