🚀 go-pugleaf

smiteq@powerup.com.au (Doug Sm... Well, James Kirk actually.) writes:

>ereyes@openix.com (MannyR) wrote:

>>          Then I tried to tinker with the jumpers in the 3.5 floppy 
>>drive. I place the jumper to MD setting - figuring that that was Master 
>>drive. 

You shouldn't have to tinker with anything but the terminating resistor
array (or switch, depending on the model drive).  In the floppy world
there's no concept of "Master" drive, only first ("A:") or second ("B:"),
and in the PC world that's determined by which ribbon cable connector
is plugged into the drive (before or after the twist in the select wires)
and (in some machines) the CMOS options.

>>         When I powered on the computer, only the fan worked. I cannot 
>>hear the cpu start or the booting. It seems that there is no power being 
>>delivered to the motherboard.

Are you saying this because you've actually measured the DC voltages,
or because the system doesn't boot?  If the latter, there are many 
more likely explanations than a dead power supply.

If you've had the system case open and have been mucking around in
the machine's guts, I would *always* be concerned about the possibility
of static damage.  All it would take is for one of the chips to be 
blown and the system won't try to start, since quite a lot of the 
system logic is required to be working before anything interesting
can take place.

Or you might just have a connector that isn't completely in its
socket.  

>There's a little pulse called a "power good signal" that the mother
>board returns to the power supply before it can deliver regulated
>power to the board.

Um...not so. 

"Power Good" is an *output* line from the power supply to the system
board, not a returned signal to the power supply.  It's also a level
signal, not a pulse, although the system board boot logic uses 
edge triggering on its rise.

"Power Good" is a status report to the system board that the power 
supply is delivering its output voltages (+5, +12, -12 VDC) within
specified tolerances; it will rise no earlier than 100 msec after
the outputs voltages are within tolerance.  The rise of Power Good
is what triggers the boot process at power-on time; a common hardware
mod for machines that don't have a hardware reset switch is to 
install a push button that momentarily grounds the Power Good lead,
so when the button is pressed and released the system BIOS is forced
to jump to the start of the boot code.

Power Good will fall if either the DC output voltages go out of 
tolerance, or if the AC input to the power supply fails.  In the case
of AC input failure it will theoretically fall at least one msec 
before the DC output voltages will reach their regulation limits.

>If you can't get the signal, you've done something wrong... Like
>setting jumpers on a floppy drive to a conflicting setting and/or
>connecting the data cable with pins 1,2 on the wrong end of the pin
>bank.

>Maybe you've connected the CD ROM backwards too. With some brands of
>drives this guarantees a burnout. 

One thing that gripes me to no end is the number of vendors that
build motherboards and drives that don't key the connectors.  I just
finished a series of hardware evaluations, and only one of the vendors
had keyed IDE connectors on the motherboard...and one of the two IDE
cables plugged into the connectors wasn't keyed.  One of the el cheapo
systems I looked at used floppy *and* IDE drives with unkeyed connectors.

>                                   I'd say at this point you have no
>alternative but to seek help from a technician or at least someone who
>has more knowledge of computers than you do because any further
>fiddling could trash you "mate's" computer.

Agreed.  

Joe Morris / MITRE