Deskpro EN: No Power

Dave has some good points as usual

However, having rambus rimms it is not a good troubleshooting move to
strip it down to one module as they need to be installed in pairs.

Also note that if there are more than two RIMM slots, the unused ones
probably need to have continuity modules (blanks) installed.

Not having the continuity modules installed may not be your only problem.
I would imagine you should get some sort of response when powering on, but
then again this is a compaq...

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Someone gave me a Compaq Deskpro EN 820 P667 recently. It came with no RAM,
but I put a pair of 128 MB RDRAM RIMMs (Rambus) in it. When I press the
power switch I get nothing; no fan, no lights. I've tried two different
cables and I've disconnected all drives, but still nothing. Could this be
anything else other than a power supply or power switch problem? Yes, it is
plugged in.

Mike

On Mon, 8 Dec 2003 16:41:25 -0600, "Mike Bresnahan"
wrote:

Someone gave me a Compaq Deskpro EN 820 P667 recently. It came with no RAM,
but I put a pair of 128 MB RDRAM RIMMs (Rambus) in it. When I press the
power switch I get nothing; no fan, no lights. I've tried two different
cables and I've disconnected all drives, but still nothing. Could this be
anything else other than a power supply or power switch problem? Yes, it is
plugged in.

Mike


Sure, it could be (anything) other than power supply or switch,
without more testing and troubleshooting measures we can only give
you odds... the odds are it's the motherboard or power supply.

The switch is quite easy to check though, with a continuity tester on
the plug or just shorting the two relevant pins on the board that the
switch connects.

Power supply isn't much harder to check IF it's standard, just unplug
the leads from everything but one hard drive, plug it back into the AC
wall outlet then short the PS_On wire to ground, at which point the
power supply fan and hard drive should be spinnning.
http://69.36.189.159/usr_1034/atx_on.gif

If that works then try stripping the system down to just minimal
essentials to get it to POST, including CPU fan, video, 1 memory
module.

Before any of that I'd try clearing the CMOS though, there's a jumper
or just remove the battery for 10 minutes after unplugging the AC
power to power supply.


Dave

Sure, it could be (anything) other than power supply or switch,
without more testing and troubleshooting measures we can only give
you odds... the odds are it's the motherboard or power supply.

The switch is quite easy to check though, with a continuity tester on
the plug or just shorting the two relevant pins on the board that the
switch connects.

Power supply isn't much harder to check IF it's standard, just unplug
the leads from everything but one hard drive, plug it back into the AC
wall outlet then short the PS_On wire to ground, at which point the
power supply fan and hard drive should be spinnning.
http://69.36.189.159/usr_1034/atx_on.gif

If that works then try stripping the system down to just minimal
essentials to get it to POST, including CPU fan, video, 1 memory
module.

Before any of that I'd try clearing the CMOS though, there's a jumper
or just remove the battery for 10 minutes after unplugging the AC
power to power supply.

Thanks much! However, the power supply apparently has a custom connector.
It has 2 rows of 12 pins instead of 2 rows of 10 pins. The wire colors are
different also.

Mike Bresnahan

On Tue, 9 Dec 2003 19:12:36 -0600, "Mike Bresnahan"
wrote:

Sure, it could be (anything) other than power supply or switch,
without more testing and troubleshooting measures we can only give
you odds... the odds are it's the motherboard or power supply.

The switch is quite easy to check though, with a continuity tester on
the plug or just shorting the two relevant pins on the board that the
switch connects.

Power supply isn't much harder to check IF it's standard, just unplug
the leads from everything but one hard drive, plug it back into the AC
wall outlet then short the PS_On wire to ground, at which point the
power supply fan and hard drive should be spinnning.
http://69.36.189.159/usr_1034/atx_on.gif

If that works then try stripping the system down to just minimal
essentials to get it to POST, including CPU fan, video, 1 memory
module.

Before any of that I'd try clearing the CMOS though, there's a jumper
or just remove the battery for 10 minutes after unplugging the AC
power to power supply.

Thanks much! However, the power supply apparently has a custom connector.
It has 2 rows of 12 pins instead of 2 rows of 10 pins. The wire colors are
different also.

Mike Bresnahan

If you have the power supply I think you might, they are a royal
PITA, and if either of the two most likely things are damaged (the
motherboard or power supply) it will most likely cost WAY more than
the machine is worth to get the proprietary parts from Compaq.

Since the system is only a 667MHz P3, it would be more time and
cost-effective to part it out, or build into that case if it can be
modified to accept a standard ATX power supply (which from my last
encounter with their non-standard shape power supplies, the case will
need cut and drilled around the back mounting to get a standard power
supply to fit.


Dave

If you have the power supply I think you might, they are a royal
PITA, and if either of the two most likely things are damaged (the
motherboard or power supply) it will most likely cost WAY more than
the machine is worth to get the proprietary parts from Compaq.

Since the system is only a 667MHz P3, it would be more time and
cost-effective to part it out, or build into that case if it can be
modified to accept a standard ATX power supply (which from my last
encounter with their non-standard shape power supplies, the case will
need cut and drilled around the back mounting to get a standard power
supply to fit.

Do you happen to know which pin is PS_ON?

Mike

On Wed, 10 Dec 2003 08:21:01 -0600, "Mike Bresnahan"
wrote:

If you have the power supply I think you might, they are a royal
PITA, and if either of the two most likely things are damaged (the
motherboard or power supply) it will most likely cost WAY more than
the machine is worth to get the proprietary parts from Compaq.

Since the system is only a 667MHz P3, it would be more time and
cost-effective to part it out, or build into that case if it can be
modified to accept a standard ATX power supply (which from my last
encounter with their non-standard shape power supplies, the case will
need cut and drilled around the back mounting to get a standard power
supply to fit.

Do you happen to know which pin is PS_ON?

Mike


I can only guess... If the PS-On functions the same as a standard ATX
power supply you can take voltage readings relative to the case (as
ground), and there would normally be only the PS-On and the standby
circuits with a voltage... The last 24-pin Compaq PSU I saw had 5VSB
AND 3VSB, so there would be 3 pins total with significant voltage
readings.

I'll post what I saw as the pinout for a 24-pin power supply, but
unlike a standard power supply, this particular power supply did NOT
come on when the PS-On is pulled low to ground. There might've been
something I missed or it's even possible the power supply was dead or
defective but in my own mind I assume that they won't turn on by
simply shorting the PS-On to ground.

Anyway I don't guarantee this is the pinout for yours but it was
verified at the PCB for the last one I saw. It was originally taken
from another usenet post, slightly edited (IIRC) as I examined the
opened PSU:

Pin # STD ATX 12V Compaq 24-pin

1 +3.3 VDC +3.3 VDC Brown
2 +3.3 VDC +3.3 VDC Brown
3 COM COM Black
4 +5VDC +5 VDC Red
5 COM COM Black
6 +5 VDC +5 VDC Red
7 Com Aux Gnd (from aux board) Grey
8 PWR ok N/C
9 +5V SB +5 (from aux board) Turquoise
10 +12 VDC +12 VDC Orange
---------------------------------------------------------------
11.1 +3.3 VDC +3.3 (from aux board) Pink
11.2 3.3V sense
12 -12 VDC Fan CMD White w/ Red Stripe
13 COM +3.3 VDC Brown
14 PS - On +5 VCD -12V? Blue (-12V)
15 COM COM Black
16 COM Power On White (ONSTBY)
17 COM COM Black
18 -5V COM Black (2nd wire, black RTNRS)
19 +5 VDC COM Black
20 +5 VDC +3.3 VDC Brown
21 ------ +5 VDC Red
22 ------ +5 VDC Red
23 ------ +3.3 VDC Sense Brown (3VRS)
24 ------ Fan_sink White w/ Blue Stripe


There is a Compaq 24-pin power supply for sale at Directron, but I'm
not even sure if it's compatible with the above pinout (I suspect it
is but being Compaq...) , let alone if it's compatible with what you
may have:


http://store.yahoo.com/directron/ps72012c.html



Dave

Has anyone used a compaq power supply on a 20 pin atx motherboard? I
bought one of those 24 pin to 20 pin adaptors and most everything
looks in order except for a few of the pins. Are any of the 3.3 or
-12 volt pins on the compaq power supply supposed to mix with any of
the other 12 volt or 3.3 volt pins on the 20 pin side of the
connector?

Chris

On Thu, 11 Aug 2005 23:31:17 GMT,
lid (mstngGT_chris_01)
wrote:

Has anyone used a compaq power supply on a 20 pin atx motherboard? I
bought one of those 24 pin to 20 pin adaptors and most everything
looks in order except for a few of the pins. Are any of the 3.3 or
-12 volt pins on the compaq power supply supposed to mix with any of
the other 12 volt or 3.3 volt pins on the 20 pin side of the
connector?

Chris


I may've missed the front-end of this thread but there are
two general types of Compaq PSU i've seen used in the past
few years. One is a standard ATX and the other is a
proprietary (pinout, but comes in several different wattages
and systems) unit that cannot be used on any other standard
motherboard. I don't know exactly what your adapter is like
though...

You won't "usually" need -12V on any remotely modern
motherboard. Some Compaq PSU had a 3.3VSB (standby) power
rail that is not connected (do not connect it) to any
motherboard rails, not to the main 3.3V power rail either.

The best thing to do is plug an AC cord into the Compaq PSU
and take voltage readings on all wire-groups (colors). Note
what's live without the PSU being plugged into anything (Not
even the motherboard) and which pin #s these live pins are.
Compare that to a standard ATX which should only have power
on the 5VSB and PS-On pins.
http://69.36.189.159/usr_1034/atx_on.gif

With the Compaq PSU connected to nothing but a HDD on one of
it's 4 pin connectors, see if you can determine the 5VSB pin
and jumper it to any ground lead with a paperclip. The PSU
should then turn on, it's fan spinning and the connected
drive spinning as well. If you can't get it to at least do
that much without it connected to the motherboard, there is
no point in trying to run the motherboard at all as that is
similar enough to the environment needed when the
motherboard would turn the PSU on.