presario 4764 power supply start up ?

[Kevin Falconer]

I was just given a presario 4764 that had been working but then just quit..
no fan, no boot up, nothing. I installed a new power supply and still nothing.
I'm told the power supply will not come on without a signal from the MB. Anyone
know if perhaps a dead battery supply on the MB would prevent the main power
supply from coming on ? I have a hard time believing I got a bad power supply.
I dont want to dump the computer if perhaps a new battery on the MB will fire
up the power supply, thanks in advance for any comments.

Kevin Falconer Fort Myers, FL

 

[Sam Goldwasser]

I was just given a presario 4764 that had been working but then just quit..
no fan, no boot up, nothing. I installed a new power supply and still nothing.
I'm told the power supply will not come on without a signal from the MB. Anyone
know if perhaps a dead battery supply on the MB would prevent the main power
supply from coming on ? I have a hard time believing I got a bad power supply.
I dont want to dump the computer if perhaps a new battery on the MB will fire
up the power supply, thanks in advance for any comments.

Kevin Falconer Fort Myers, FL

A problem with the CMOS settings can prevent startup. Try resetting
the CMOS - there is probably a jumper for that. Check the CMOS battery.

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[Brian Friedl]

Was this computer working while you had it? It sounds like the
motherboard or CPU has problems. There is a very remote possibility that
it is the battery. However, this signal the SMPS (switch mode power
supply) receives from the MB is really from the SMPS. When you press the
power button on a ATX computer, it requires a working CPU to tell the
SMPS to turn on.

Steps to check:
1. Swap out CPU if possible.
2. Unplug switch from MB and try shorting out the 2 pins on the MB
3. Go get a new computer

 

[kony]

Was this computer working while you had it? It sounds like the
motherboard or CPU has problems. There is a very remote possibility that
it is the battery. However, this signal the SMPS (switch mode power
supply) receives from the MB is really from the SMPS. When you press the
power button on a ATX computer, it requires a working CPU to tell the
SMPS to turn on.

Steps to check:
1. Swap out CPU if possible.
2. Unplug switch from MB and try shorting out the 2 pins on the MB
3. Go get a new computer

It does not require a working CPU tturn on a power supply, in general,
nor memory, battery or other parts installed unless Compaq did
something unusal to the motherboard, which isn't all that unusal for
Compaq.

On the other hand, a CPU or other component that's shorting out could
cause a problem, so any and all questionable parts can be removed from
the motherboard. Considering that this may not even be an ATX power
supply, if it's an AT it can be unplugged from the motherboard
altogether and just plugged into one drive for a power-on attempt, or
if an ATX just ground the PS-On pin in addition to above.

The power supply might be checked to confirm that it's input voltage
switch is set appropriate to the location, but otherwise that system
is better retired for something more modern, standard, and of course,
working.

We might (or might not) be able to help more with a better description
of the system, the motherboard and power supply type, as much detail
about them as possible including the connector type and existance of
external switches. Compaq also sold some systems (don't recall model
numbers) with AT power supplies, having a rocker switch on the back
for the AC input and a switch on the front bezel but the switch on the
front wasn't actually a power switch, was a sleep switch. Those
systems never turned off except by the back switch and I don't think
the user was supposed to turn them off in back, just leave them
running in sleep mode... leave it to Compaq to take perfectly working
standard designs and create a problem.


Dave

 

[Sam Goldwasser]

A corrupted CMOS may inhibit power on.

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[kony]

A corrupted CMOS may inhibit power on.

It can prevent the system from POSTing, but without a viable BIOS,
even without the EEPROM in the board it should still be able to pull
the PSU power-on pin low, turn on the power supply so at least it's
fan would be spinning and voltage levels obtainable.

The question at this point might be, "Which fan isn't turning?".
Apparently some Compaq systems do use logic for the CPU fan control,
it may not spin but the power supply fan should still be on.


Dave

 

[Sam Goldwasser]

It can prevent the system from POSTing, but without a viable BIOS,
even without the EEPROM in the board it should still be able to pull
the PSU power-on pin low, turn on the power supply so at least it's
fan would be spinning and voltage levels obtainable.

Apparently not. I had a Compaq system which played totally dead and resetting
the CMOS fixed it.

The question at this point might be, "Which fan isn't turning?".
Apparently some Compaq systems do use logic for the CPU fan control,
it may not spin but the power supply fan should still be on.

Nothing, dead as a door stop.

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[kony]

Apparently not. I had a Compaq system which played totally dead and resetting
the CMOS fixed it.

Hmmm. Leave it to Compaq to "fix" something that isn't broken...
every motherboard I've ever tried will turn on a power supply without
anything, even the EEPROM, plugged into it. Makes sense though, since
they often solder the EEPROM to the PCB.

Nothing, dead as a door stop.

I'm not entirely clear on which board the original poster had, perhaps
that info would help... possibly I have one here but once it's pulled
from the original case it's hard to tell


Dave

 

[Kevin Childers]

Yes, but from the sound of it the original poster is referring to a AT,
not ATX board. On those, the fan is wired to the main power circuit and
comes on when the power is turned on at the front of the machine. Later ATX
models had the power managed through the board.

KC

 

[Kevin Falconer]

1. Swap out CPU if possible.

not possible, soldered in

2. Unplug switch from MB and try shorting out the 2 pins on the MB

which two pins ?

3. Go get a new computer

got one, just trying to get this one going for company to use,
games and such

thanks for the comments....

Kevin

 

[BFriedl]

what are the specs on this system? Im guessing its an AT computer. Does
the power switch stay in when you press it or is it a momentary switch?
If it stays in, then you have a AT which makes it easier. You can just
plug in a hard drive (to give it load) and turn on the psu. If that
doesnt work,then its either your hdd or the psu.

not possible, soldered in




which two pins ?




got one, just trying to get this one going for company to use,
games and such

thanks for the comments....

Kevin

--
BFriedl
A+ Certified Technician
AIM: UACybercat
** Bear Down Arizona! **
******* Go Cats! *******

 

[Kevin Falconer]

what are the specs on this system? Im guessing its an AT computer. Does

the power switch stay in when you press it or is it a momentary switch?
If it stays in, then you have a AT which makes it easier. You can just
plug in a hard drive (to give it load) and turn on the psu. If that
doesnt work,then its either your hdd or the psu.

bfriendl, the switch on front is just a momentary switch, it's a
sleepmode switch. The PSU has a rocker switch on the back for on/off
I think. I'll
probably call compaq. I thought I ordered this from compaq but I think
it
was PC/finder ? but the PSU has compaq on it. I suppose I'll try
compaq
but they charge also for their tech info. If i knew for a fact this
PSU did
not require a turn on signal from the board I would just call the
shipper and tell them I'm sending it back, but if it's good I'd just
be wasting more time.
The p1 and p2 connectors are like this ------ ------ then one other
connector in the middle of board ------
the green wire I was told to jumper to ground is in the 6 pin
connector in the center of the board, i think this is p9 connector


Kevin

 

[Kevin Childers]

bfriendl, the switch on front is just a momentary switch, it's a
sleepmode switch. The PSU has a rocker switch on the back for on/off
I think.

Actually it covers all three functions, on/off/sleep. Usually it must
be held down for 4 seconds to turn off the system. A good thing if you have
a button pushing two year old wandering through your work area.

I'll probably call compaq. I thought I ordered this from compaq but I think
it was PC/finder ? but the PSU has compaq on it. I suppose I'll try
compaq but they charge also for their tech info. If i knew for a fact this
PSU did not require a turn on signal from the board I would just call the
shipper and tell them I'm sending it back, but if it's good I'd just
be wasting more time.

You can also try www.power-on.com they have had simular PSUs in the
past.

The p1 and p2 connectors are like this ------ ------ then one other
connector in the middle of board ------
the green wire I was told to jumper to ground is in the 6 pin
connector in the center of the board, i think this is p9 connector

Make sure you have the two black leads on P1 & P2 side-by-side. The
other connector is unique to only a few boards. It, I believe, is a control
circuit allowing the basically AT board to perform some functions that later
came out ass standard for ATX boards.

KC

 

[Kevin Falconer]

Actually it covers all three functions, on/off/sleep. Usually it must

be held down for 4 seconds to turn off the system. A good thing if you have
a button pushing two year old wandering through your work area.

Thanks, the one thing i did not do is hold that front button in for
anything longer than a quick push. I'll crap if i was just not holding
this button in long enough to wake up the power supply, probably
wishfull thinking,
but i'll give it a try !