MOTM

Are you absolutely certain beyond any doubt that you didn't have it
in backwards? Electrolytics leak more with temperature, and heat up
as they leak, so if they're ever put in backwards, you could have
from 5 minutes to several hundred minutes before they burn out.
Some of them burn out most spectacularly, waiting until the temp
is higher than the flashpoint of the electrolyte, in which case
miniature fireballs are launched from the printed circuit card.

-bobC

-----Original Message-----
From: media.nai@... [mailto:media.nai@...]
Sent: Sunday, April 27, 2003 9:08 AM
To: motm@yahoogroups.com
Subject: [motm] 700 problem and solution



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.





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