wrote in message
ps.com...
On Nov 8, 4:49 am, "Arfa Daily" wrote:
Well, I would have to say that it certainly indicates that you are not
chasing down any kind of permanent 'short' on your 5v rail. So now that
you
know where the 5v rail comes off the end of the LM317 (was it ?), can you
disconnect it from that point, leave the fuses out of the 12 and 30v
feeds,
and hook the unit back to line power, with a 5v fuse in place ? Measure
the
IN, SET and OUT pins of the '317 to see what you get, and if you get a
correct 5v on the OUT pin[...]

If the voltage isn't correct (e.g. 4.8-5.2V) at that point (but the
fuse isn't
blown) tack a 470 ohm resistor from the OUT pin to GND. The LM317
has
a load regulation spec of 10 mA, and a minimum operating current of
~1mA
(for low Vi-Vo); the adjust resistors may not be small enough to draw
this
much. And don't isolate the regulator by lifting the OUT pin, or
you'll lose
the adjust resistors.

TM


Yes, good advice. Looking again, it seems it is an L387 regulator. I'll have
to look that one up. It's so hard to cover all bases with someone who's at
the 'practice' level. Things like making sure that the V-set resistors are
still connected, is second nature when you do this sort of stuff all the
time ...

Arfa