[Coco] NitrOS-9 newbie needs some help (More data)

[KnudsenMJ at aol.com]

In a message dated 8/11/04 3:25:53 PM Eastern Daylight Time, 
kevdig at hypersurf.com writes:

>   Could the problem be the power supply on this thing?
>  These things don't exactly have NASA spec power supplies. Maybe
>  you can carefully bypass it with a PC supply.

I had a funny power supply problem on one of my floppy disk drive cases, 
which was holding two half-height drives that started acting totally flaky one day.

Most power supplies have a full-wave diode bridge (or a full-wave pair of 
diodes using a center-tapped transformer secondary winding), so that both halves 
of an AC power waveform contribute DC charge to the output capacitor.


One of the diodes had come loose from the circuit board, and I was getting 
only half-wave rectification.  Under light loading, this was good enough, since 
my capacitor was still in good enough shape to hold the charge between cycles. 
 But with both drives in action, the DC voltage developed "holes" at 60 holes 
per second, and things got very strange.

Resoldering the diode restored proper operation.  You might have a failed 
open diode (internal fault).  Just one more thing to check for.

Try using a known accurate, precise (probably digital) voltmeter to check 
your +5 power busses.  Anything under 4.95 probably indicates an open diode or 
dried-out capacitor.  --Mike K.