Q-Tec power supply problems with A7N8X

[Vormulac]

Hi all,

Having heard good things about them, I tried to install a Q-Tec 650w triple
fan PSU at the weekend and encountered a problem, wondered if anyone had
seen anything like this?

The PSU appears to work when connected up, ie the motherboard power light
comes on (A7N8X-Deluxe by the way) but when the on-switch is thrown, the
case fans connected to the PSU spin up, but not the fans connected via the
motherboard, and there's no indication the board is making any attempt to
boot.
However, take it out, and try again at some point in the future and it
works, but not with enough regularity to put it in the case and expect to
have a working pc.

There seemed to be no pattern to it working/not-working, I just wondered if
anyone was aware of any power supply compatibility issues with this
brilliant motherboard, or whether as I suspect, the PSU is just duff.

I really do want to get this sorted, as I have just added an XP3200 cpu and
a 9800XT to my system, so my old Enermax 350w psu is going to be a little
stressed and I want to avoid any stability problems.

Thanks alot for any thoughts.

Vormulac
remove n0spam from email address to reply

 

[Ben Pope]

Hi all,

Having heard good things about them, I tried to install a Q-Tec 650w
triple fan PSU at the weekend and encountered a problem, wondered if
anyone had seen anything like this?

Well, they're underrated, but the 650W should be plenty for any sensible
system. Running a Barton 2500, same mobo, 9800 Pro, two WD hard rives, 2
DVDs, and the Q-Tec 550W Dual Fan Gold is fine.

The PSU appears to work when connected up, ie the motherboard power light
comes on (A7N8X-Deluxe by the way) but when the on-switch is thrown, the
case fans connected to the PSU spin up, but not the fans connected via the
motherboard, and there's no indication the board is making any attempt to
boot.
However, take it out, and try again at some point in the future and it
works, but not with enough regularity to put it in the case and expect to
have a working pc.

There seemed to be no pattern to it working/not-working, I just wondered
if anyone was aware of any power supply compatibility issues with this
brilliant motherboard, or whether as I suspect, the PSU is just duff.

When it does work, what do the voltages read?

I really do want to get this sorted, as I have just added an XP3200 cpu
and a 9800XT to my system, so my old Enermax 350w psu is going to be a
little stressed and I want to avoid any stability problems.

Check the specs of the two PSUs and see what the max current is, I doubt
you'll see twice the current

Your Enermax probably would be stressed.

As to the problem... it's a good one, is the 110/220V switch right? Not
sure what happens when you get it wrong...

Ben

 

[Paul]

Hi all,

Having heard good things about them, I tried to install a Q-Tec 650w triple
fan PSU at the weekend and encountered a problem, wondered if anyone had
seen anything like this?

The PSU appears to work when connected up, ie the motherboard power light
comes on (A7N8X-Deluxe by the way) but when the on-switch is thrown, the
case fans connected to the PSU spin up, but not the fans connected via the
motherboard, and there's no indication the board is making any attempt to
boot.
However, take it out, and try again at some point in the future and it
works, but not with enough regularity to put it in the case and expect to
have a working pc.

There seemed to be no pattern to it working/not-working, I just wondered if
anyone was aware of any power supply compatibility issues with this
brilliant motherboard, or whether as I suspect, the PSU is just duff.

I really do want to get this sorted, as I have just added an XP3200 cpu and
a 9800XT to my system, so my old Enermax 350w psu is going to be a little
stressed and I want to avoid any stability problems.

Thanks alot for any thoughts.

Vormulac
remove n0spam from email address to reply

The qtec.info site doesn't list the output specifications for
their power supplies. Just the color and number of fans

This review site has a picture of a Q-tec PSU label, and one thing
missing from the label, is whether any of the outputs have a
minimum loading specification. It is possible your new PSU is
operating out of spec, because your motherboard presents too
small a load. This is one of the problems with buying the biggest
supply you can find - it can actually be too big.

http://www.bit-tech.net/review/123/

To estimate your power consumption, here are some estimates:

From this site: http://www.qdi.nl/support/CPUQDISocketA.htm
2200 (3200+) OPGA 200 512 1.65 V 85C 60.4 W

If the 60.4 watts was drawn from +12V, that would be 5A of current,
and if the Vcore conversion was 80% efficient, then you would need
6.25A from +12V. There is only one wire on the ATX 20 pin power
connector for +12V, and a single pin is rated for 6 amps, so it
is unlikely the processor is powered by +12V. (There is no ATX12V
2x2 connector on the motherboard.)

Vcore could be powered by +5V, and in that case, you would need
12 amps of current, and at 80% efficiency, 15 amps of current
would be required from +5V. There are four +5V pins on the ATX 20
pin connector, which gives a capacity of 24 amps of current before
there would be a problem with the pins on the connector.

+5V estimates

1A per disk drive or CDROM/DVD/writer etc
15A for Vcore conversion, to power the processor
5.5A for 9800Pro 128MB (my card, measured) - scale by clock rate
for your video card.
Any other +5V loads, such as your average PCI device, is probably
negligible.

+12V estimates

0.5A per disk drive (at idle). They draw 2amps during spinup, but
that lasts only a short time at powerup.
1A total for case fans (you can read the actual numbers off the fans)
1A for 9800Pro 128MB (my card, measured) - scale by clock rate
for your video card.

On an AthlonXP board, it looks like +5V is more heavily loaded than
+12V. I would want to see at least 25A at +5V (not all of it flows
through the ATX 20 pin connector). The +12V only needs maybe 4 or 5
amps at +12V, which can be met by virtually any ATX full size
supply. (Intel P4 boards are different, in that they need
15A to 20A at +12V, and much less for +5V.)

I'm not sure a 650W supply is needed.

Looking at a table of Antec supplies:

VOLTAGE +5V +12V +3.3V -5V -12V +5VSB

TRUE330 30A 17A 28A 0.5A 1.0A 2.0A
TRUE380 35A 18A 28A 0.5A 1.0A 2.0A
TRUE430 36A 20A 28A 0.5A 1.0A 2.0A
TRUE480 38A 22A 30A 1.5A 1.0A 2.0A
TRUE550 40A 24A 32A 0.5A 1.0A 2.0A

even the True330 can power your system. If you have a few more
dollars to spend, a True430 leaves a bit more margin against my
sloppy estimates.

You didn't state what kind of Enermax supply you've got, so I
just dug up the specs for EG365

http://www.enermax.com.tw/products_page.php?Tid=1&gon=231&Gid=18&Gid2=22

VOLTAGE +5V +12V +3.3V -5V -12V +5VSB

EG365-VE 32A 26A 32A 1.0A 1.0A 2.2A

(Combined +5 and +3.3 power less than 185W. 5V@25A is 125W, and that
leaves about 18A of room on the 3.3V output, before the combined power
is exceeded.)

I would say even the EG365 would be good enough to run your system.

I wish I could say more about the Q-tec, but if Q-tec doesn't offer
technical data for their products, then saying anything about the
product would be opinion and not fact.

Note that my efficiency estimate for Vcore conversion is on the
low side. I think Vcore conversion is actually more efficient
than 80%, and the way to tell, is to feel the components, to see
if they get hot. The less heat you feel, the more efficient the
circuit is operating. It is quite possible the Vcore is more like
90% efficient, but I like to err on the safe side, and that is
where the more conventional 80% number comes from. Note that
ATX supplies are even less efficient, with the worst supplies
being just 68% efficient, from the AC line.

Maybe you can trade the Q-tec in on a brand name supply ?

HTH,
Paul

 

[Ben Pope]

The qtec.info site doesn't list the output specifications for
their power supplies. Just the color and number of fans
<SNIP>
I wish I could say more about the Q-tec, but if Q-tec doesn't offer
technical data for their products, then saying anything about the
product would be opinion and not fact.

For the 550W Dual Fan Gold (PFC):

3.3V 30A,18A
5V 40A, 30A
12V 20A, 16A

3.3V + 5V lines max 285W
12V line max 240W

As you can see, the ratings (which total over 500W, most of the rest being
the few other low current lines) are much closer to the Max current, rather
than the continuous currant drain, which is somewhat misleading.

It's probably also rated at some silly temperature like 25°C, of course, the
ability to supply current is reduced as heat rises.

Ben

 

[Paul]

As to the problem... it's a good one, is the 110/220V switch right? Not
sure what happens when you get it wrong...

Ben

Now, that is an interesting observation. I did notice while searching
for documentation on the supply, that in a picture of the supply,
the clever Q-Tec lads, stuck a label saying "230V" above the hole
for the power plug. I don't see a switch to set the voltage to 110/220V.

http://www.qtec.info/products/productpic.htm?artnr=14103&image=14103.jpg

Maybe there are different versions of the design - one for 110V
countries and one for 220V countries ?

I think your observation could be "right on the button".

Paul

 

[Ben Pope]

Now, that is an interesting observation. I did notice while searching
for documentation on the supply, that in a picture of the supply,
the clever Q-Tec lads, stuck a label saying "230V" above the hole
for the power plug. I don't see a switch to set the voltage to 110/220V.

http://www.qtec.info/products/productpic.htm?artnr=14103&image=14103.jpg

Maybe there are different versions of the design - one for 110V
countries and one for 220V countries ?

I think your observation could be "right on the button".

There's no switch on mine either... only 230V.

OP looks like he's from the UK, so is probably alright on that one... unless
you bought a "foreign" PSU.

Ben

 

[Vormulac]

There's no switch on mine either... only 230V.

OP looks like he's from the UK, so is probably alright on that one...
unless you bought a "foreign" PSU.

Ben

As you correctly observe, I'm in the UK and I've got a UK purchased 230V
unit.
This is most perplexing, but thanks to you all for your input.