micky said:
Those numbers I gave you, 10.9 for one 12 volt pin and 11.5 for the
other** were indeed no load readings. (All the other readings were
very close to nominal, 3 and 5.)
**I didn't note positive or negative. I assumed those were correct)
Well, a friend gave me a bunch of PSUs, and the first two were 235
watts instead of the 275 Silencer (PC Power and Cooling) that I've
been using, but I figured I should test them before installing them.
First one tested dead and then the other. I don't mind him giving me
his junk, but I'm surprised he let it sit around his own apartment
without marking it as bad.
The next one I tool out of a young friend's junk computer and all the
pin voltages were wrong.** Not dead but worng. One was over 12v,
16v iirc.
Finally I found one from the first friend that was still in the
wrapping bag. Also a Silencer, Brand new, and 275 watts.
I tested it and the votlages were all good except the 12 volt pins
were actually a little lower than the one I removed!!!
Rather than install it, I just plugged in the 20-pin conector and
ignored alll the plugs to the CDs, the floppies, harddrrive,, the
extra fan.
That should be okay, shouldn't it?
Turned it on, green light goes on, red light goes on, and still
displays nothing on the monitor.
Doesn't beep either. (I may have unplugged the USB keyboard, but I
don't remember right now.)
Question about the AGP video card in the AGP slot. At the bottom
corner of the card, the blank circuit board has an L-shaped part that
I thought was supposed to hook onto a tab at the end of the slot.
But it seems to just slide into the slot at the same time all the
contacts and the rest of the board slide into the slot. I couldn't
manage to hook it onto anything. I installed ti right, didn't I?
**I don't remember if it was a Dell, but I guess so. I'm going to
call him to make sure. No indication on the Delta Electronics case
that it was meant for a Dell!! .DPS-200PB-101
With a suffix F it's used in a Compaq
One word of warning, is Dell computers had a period of product years,
where the wiring on the main power connector was non standard.
If you're going to pick through a junk pile, it's a good idea
to verify wire color. As long as the manufacturers of the supplies
stick to the standard color scheme (i.e yellow = 12V), then you can
detect a "Dell specific" supply from an "ATX standard" supply. For
a reference on color codes to expect, you can use an ATX spec.
http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf (page 30)
You would at least, compare the wire color of your (previously working)
ATX supply, to any new supply you want to test out.
In terms of power rating, you want to check the label on the supply,
and see if it has adequate +5V amps. On my Nforce2 Athlon system,
that number was around 25 amps, which left a bit of room for
the +5V current my video card was using. If those 250 or 275 watt
supplies have relatively low 5V ratings, they might not be the
best choice for a substitute.
*******
To complicate matters, supplies come in two types. One type is the
"honest" type. The label contains both maximum and minimum current
ratings. The "minimum" value tells you that the supply may not
regulate the rail properly, under "no load" conditions. For
example, if you have a supply with a 12V 1A minimum spec, then
if you disconnect all 12V loads, the output won't read 12V. No
damage should result, but the +/-5% spec in the ATX standard
may be violated. That might be viewed as an admission they
don't meet crossloading specs, and by putting the information
on the label, there should be no surprises.
The other kind of supplies, only have maximum current values
listed. With those, we *assume* the supply stays in regulation
all the way down to zero.
When probing your existing power supply, you want to do as follows.
ATX ------- +5V/+12V ------ disk#1 ----- disk#2 ----- Disk#3
Supply ------- +5V/+12V <--- Cable with no loads connected
You take a reading off both cables. The "cable with no loads connected"
gives a "true" reading of current output voltage. Taking a reading
off the end of the first cable, would show the impacts of R * I
voltage drop.
If you read the second cable, and it reads 12V, then you check the first
cable, and it reads 11V, you might conclude from that, that there
is too much resistance in the cabling to support that amount of
peripheral loading.
If both cables read 10.6, especially the no-load cable, then you might
conclude the power supply is out of spec. If the offered load is
below the "minimum" current specified on the label, then you
have your explanation. 10.6 volts is too low to run a hard drive,
so the hard drive may refuse to spin up, or may spin up and then
spin down, over and over again.
A standard supply works roughly as follows. There is a transformer
in the supply. The primary side has high voltage chopped DC on it.
The output voltage is established by "turns ratio" of the transformer
windings. Rectifiers at the output, convert the AC from the
transformer, back into DC.
Core
||
Primary_winding ||3.3V winding
||
||5V winding
||
||12V winding
The power supply observes the outputs, and tried to compensate for
loading. If we heavily load the +5V, the power supply immediately
notices this, and "turns up" the primary. All output voltages rise.
The 5V rises, until it's close to 5V again. The 12V has now
risen above the 12V value, and might be 12.6V. You can actually
tell how the supply is being loaded, by watching the direction
the output rails are moving in. If I saw the five volt rail at
4.8V, and the twelve volt rail at 12.6V, then I conclude from
that, that the five rail is "heavily loaded".
*******
PC Power and Cooling, did make replacement supplies for Dell computers,
which means some of their products will have the "alternate wire
color" pattern and can't be used on your computer. The documentation
may have been removed from their site, as to which models were
Dell substitutes.
*******
You can use the main power connector only, if you want. As long
as the motherboard places some loading on each rail, it should
stay in spec enough to be usable. Your 12V rail will still be
used to power fans.
*******
The L-shaped AGP "heel" has two potential functions. It
can be used to keep the card in the slot, as in this example.
This shows the "slide lock" style retainer, on the AGP slot.
But there was also the spring-loaded side button heel lock,
which is more annoying to disengage.
http://www.interfacebus.com/agp-expansion-card.png
But in an AGP Pro motherboard, the heel would fit right into
the slot, where some extra power pins are located. The heel
has no electrical contacts on this, so it doesn't matter.
The heel may provide some mechanical support in that case,
but not be as secure as a card with a heel lock. AGP Pro
adds a section before and after the regular slot area.
http://www.motherboards.org/files/techspecs/apro_r11a.pdf (Fig.6 page 12)
If you own an AGP Pro card, and have an AGP Pro motherboard,
then the heel area has electrical contacts on it. Not too
many people own AGP Pro cards.
http://upload.wikimedia.org/wikipedia/commons/8/82/Quadro_ELSA_GLoria_II_Pro.jpg
Paul
