Ref ASTEC power supply from old computer model SA 147-3505 I can pick up the logic 5 volts but not the +12 volts and -12 volts .FAN not energised so I guess there needs to be an elec link via the computer switch (switch no longer available) I would be gateful for any suggestions

Mike
I take it that this is a standard power supply out of a PC (switch mode)
These are a common connection point on any brand PC
Use a DC Voltmeter to find the Ground, +5 Volt & +12 volt wires to power your 3.5 inch Hard Drive. The 2.5" Hard Drives (laptop) has only Ground (Black) & +5 Volt.

If the fans are not turning, check the 12 volts from the power supply. I would bet you need to replace the power supply. The power supply generates +5 v, -5 v, +12v and -12 v. The fans use the +12 v for power.

Power is going to the motherboard, and you know this by assuming?

An assumption would be you see the Power Supply fan spin, LED lights light up, and maybe computer case fans spin.

Not an assumption, and you would have tested the 3 main voltage power rails, coming out of the Power Supply.

The Power Supply in your computer is an SMPS.
Switched-Mode Power Supply. (Also is known as the short abbreviation - PSU. Power Supply Unit)

http://en.wikipedia.org/wiki/Switched-mode_power_supply

The Power Supply in your computer is a Converter.
It converts HIGH AC voltage into 3 LOW DC voltages.

[Depending on country,
USA = 120 Volts AC. UK = 240 Volts AC. Japan is 100 Volts AC, but may depend on area. Australia = 240 Volts AC. India = 240 Volts AC. HOWEVER, do not write the above in stone. I may have made an error ]

The 3 low main DC Voltages coming out of the Power Supply is;
A) 3.3 Volts DC
B) 5 Volts DC
C) 12 Volts DC

Orange wires carry 3.3 Volts DC
Red wires carry 5 Volts DC
Yellow wires carry 12 Volts DC
ALL Black wires are Ground wires. They can also be called Negative wires.
This is a DC circuit now. There is a Positive, and a Negative.
Orange, Red, and Yellow wires are power wires, and also Positive wires.

The first part of your diagnosis will be to test those 3 main voltage power rails.

[Digressing;
Using an example;
There are many Red wires coming out of the Power Supply.
These are 5 Volt wires. They are Connected TO, the 5 Volt power rail in the Power Supply.
ALL 5 Volt wires end in one place, in the Power Supply.
The 5 Volt power rail.
When you test just ONE red wire, you are testing the entire 5 Volt power rail coming from the Power Supply.

This also goes for the Orange wires, and Yellow wires ]

With the Red 5 Volt wires, and Yellow 12 Volt wires, you could just use a 4-pin Peripheral power cable to check them,

http://www.playtool.com/pages/psuconnectors/connectors.html#peripheral

Multimeter set to DC Voltage, the red (Positive) probe lead of the multimeter; touches the female metal terminal connector, for the Red wire.

http://www.mcmelectronics.com/product/28-9420&utm_medium=Affiliate&ref=cj&utm_campaign=CommissionJunction&utm_source=CommissionJunction?t=2&utm_expid=8634549-14

The black (Negative) probe lead of the multimeter, touches a female metal terminal connector, that goes to a Black wire.

You should be reading 5 Volts DC.

Same thing for the Yellow 12 Volt wire.

With an Orange 3.3 Volt wire, this changes.
A straightened out paperclip is inserted, down into the BACK of the ATX main power cable's connector; AND into a socket hole with an Orange wire in it.

http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain20

http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain24

The straightened out paperclip, slides down into the socket hole, with the Orange wire in it.
Slides down into the socket hole, RIGHT NEXT TO the orange insulation of the wire, and MUST go down far enough; to Touch that female metal terminal connector.

EVERY wire going down into the ATX main power cable's connector, ends in a female metal terminal connector.

Same thing is down with a socket hole that has a Black wire in it.
ALL Black wires are Ground wires. (Negative)
You can choose ANY socket hole that has a Black wire in it.

Now touch the two probe leads of the multimeter, to their respective straightened out paperclips.

Red (Positive) probe lead of multimeter, to straightened out paperclip in Orange wire socket hole.
Black (Negative) probe lead of multimeter, to straightened out paperclip in Back wire socket hole.

You should be reading 3.3 Volts DC.

(Or if your multimeter kit has special probe lead, that would take the place of a straightened out paperclip, of course use it instead)

Know this;
A) If ALL of the LED's ('lights') were on at once, they would use less than 1 Watt of power.

B) EACH fan uses 2 to 3 Watts of power.

C) A typical CPU (Processor) can use 51 to 130 Watts of power.
Just depends on what Processor (CPU) it is.

This is why a Power Supply with a weak voltage power rail, will not have enough power to turn the Processor ON, but will have enough power to light those simpy LED's, and spin fans.

[LED - Light Emitting Diode ]

Regards,
joecoolvette

The switch mode power supply could be faulty
The voltage on the red wire should read 5 volts and the yellow wire should read 12 volts..

If your power supply is rated 6 AMPS and your motor is rated 14 amps peek, then when that motor starts it will draw the 14 AMPS, That will trip the power supply right then and there. After it runs a few seconds the AMPS will drop about ½ that, but still 7 AMPS is more then the power supply is rated, so you will need a different power supply.

Power Supply.

Weak voltage power rail, or more than one.

(There are three power rails for the Power Supply used in your computer;
1) The 3.3 Volt power rail
2) The 5 Volt power rail
3) The 12 Volt power rail.

Wires with Orange insulation carry 3.3 Volts
With Red insulation carry 5 Volts
With Yellow insulation carry 12 Volts.

Each wire is connected to one power rail in the Power Supply.
{All Black wires are Ground wires}

The Power Supply in your computer is an SMPS. Switched-Mode Power Supply,

http://en.wikipedia.org/wiki/Switched-mode_power_supply )

I don't know what form factor your Power Supply is because you didn't state which model it is.
Small Form Factor (SFF)
or
Convertible Mini-Tower
or
Ultra Slim Desktop

Post additional questions in a Comment. Also state what model your Compaq Evo D510 is.

Regards,
joecoolvette

Sorry, I stepped out. Otherwise I would have answered right away.

Your power supply changes your household, (Residential),or business electricity, into three main voltages. Also converts it from AC to DC electricity.

1) 3.3 Volts
2) 5 Volts
3) 12 Volts

Each one of these voltages is a voltage power rail.
There's more involved than that, but for ease of explanation, we'll let this suffice.

A) Orange wires are 3.3 Volts. ( 3 and 3/10ths Volts. Sometimes the decimal point is hard to see on here )

B) Red = 5 volts

C) Yellow = 12 Volts

The only power cable you're going to be switching around, in my thoughts, is a 4-pin peripheral power cable.
Has a 4-pin Molex connector on the end.

http://www.playtool.com/pages/psuconnectors/connectors.html#peripheral

Note that there is one Yellow wire, one Red wire, and two Black wires.

If you have a bad 5 volt power rail, or a bad 12 volt power rail, all the peripheral power cables will be effected.

Won't do you any good changing them out.

They all derive their power from the same source.

I understand your reasoning, and it looks logical, huh? But as you can now see, it doesn't affect anything changing peripheral cables around.

The blinking Power On light indicates you have a bad power supply.
I can't find any documentation on Packard Bell's website to give you, to substantiate my statement to you.

Otherwise I would.

To test my claim.
Do you have another power supply of the same style, and has the right amount of power cables? Also should be at least 200 watt.
You're just going to use it for a test, not as a replacement power supply.

No?

You could conduct a voltage test of the power supply, but if the fan doesn't even spin, the power supply is kaput.

Does the power supply's fan spin?
If so we can go on to do a voltage test.

This will require a multimeter.
The multimeter is set to the 0-50 Volts DC scale.

An economical, but decent enough multimeter, can be purchased in a multitude of places.

An auto parts store is one place.
Radio Shack is another.
There are several stores that carry affordable ones.

Average price for a decent enough multimeter for this test is around $10 to $15.

If you do not wish to use a multimeter, there is also the option of using a simple to use power supply tester.

This is one example, and an example of where to purchase it,

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1647108&CatId=1107

Again, this is if the fan on the power supply spins. There is the rare occasion that the fan on the power supply will fail, and the power supply will work, but this is not one of those rare occasions.

Also, if the power supply fan spins a few times, then stops, the power supply is shot.

What leads to power supply failure?

A) The power supply was a low quality item installed by the computer manufacturer.
Saved the manufacturer money.

50 cents to a dollar saved, times 50,000 computers, or more of that model, adds up in a hurry.

B) The computer is dirty inside. Computers need to be kept clean on the inside, as well as their power supply's, on a regular basis.

Inside a Power Supply is a Heatsink, or more than one Heatsink.
A Heatsink is typically constructed of a flat metal base, that has tall fins protruding up from the base.

The metal base absorbs heat from whatever object is placed against it, and the heat is radiated up into the fins, where it is dissipated away.

Air flows through the fins, and helps carry the heat away.
(There is a Heatsink on top of the Processor also)

A Power Supply also has a fan.
The fan draws air into the Power Supply through the computer case, then pushes the air out of the back of the computer case.

The air drawn in through the computer case, helps to keep the hardware components inside the computer case cool, as well as the other fans that are implemented. (Computer case fan/s, Processor fan)

It also helps to keep the hardware components inside the Power Supply cool.

When the Heatsink fins are clogged with gunk, and the fan's blades, center hub, and surrounding shroud, are clogged with gunk, the cooling capacity of the Power Supply drops tremendously.

The Power Supply hardware components heat up.

Heat = Wasted Energy
The Power Supply tries to keep up with the demand for power, but with the energy loss due to excessive heat, the Power Supply hardware components eventually fail.

Typical SMPS used in a computer. (Personal Computer)

http://en.wikipedia.org/wiki/Switched-mode_power_supply

145 Watt power supply with the old style AT motherboard power cable connectors. (2 Each)

http://www.playtool.com/pages/psuconnectors/connectors.html#oldpc

I just put Astec SA147-3506 in my browser search bar, and came up with a number of search hits. Prices ranged from $50 to $170!

And it's a 145 Watt power supply! Astec is a cheap quality power supply manufacturer, to boot!

You know, there is a way to use a newer reliable power supply, and the AT power supply motherboard connectors, off of the power supply you have.

It's not for the squeamish, but can be done.

The power wires are removed from the ATX power supply motherboard cable connector, of the new power supply, and inserted into the AT power supply connectors.
(ATX 12V power supply is the newer one. AT power wires removed from the P8, and P9 connectors of your old power supply)

Interested?

Power supply failure, or the Power On switch. (Behind the Power On button)

My money's on the power supply failure.

Why?
It's the leading case of computer failure. The power supply is the 'Heart' of a computer. (Processor is the 'Brain', Motherboard is the 'Building Block')

Computer was on for an extended length of time? Was the computer ever turned off, and the inside of the computer cleaned out on a regular basis?
(Power supply also)

Normal procedure is to unplug the computer from power, open the computer case, and use a can of compressed air for computers.

Power supply light is on?
This is what is going on.

Computer power supply's are rated in Wattage, for power.
Voltage times Amperage = Wattage

The HP 5188-2627 power supply, supplies three main voltages. It has three main voltage power rails.

1) The 3.3 Volt rail
2) The 5 Volt rail
3) The 12 Volt rail

Your power supply has a weak voltage rail.

A) ALL the lights use less than 1 Watt of power.
B) EACH fan uses 2 to 3 Watts
C) A typical Processor uses 55 to 125 Watts.

There isn't enough power from the power supply to turn the Processor on.

Solution is to replace the power supply.
It may seem a little daunting for someone replacing a computer power supply, the first time.

After you have replaced one, it becomes easier.
Essentially you are just opening the computer case, unplugging the power cables from the power supply to the various hardware components, and removing the power supply.

To install just reverse these steps.

The power supply in your computer is a 300 Watt power supply. (Maximum wattage)

The size, and shape of the power supply, is one that is used in over 90% of personal computers.
ATX

What I would I recommend for a replacement?
Not one of the cheap quailty Hi-Pro's that HP used, that's for sure!

An OCZ StealthXStream 400 Watt is what I would recommend.
Why?

1) It will fit
2) It has a 140 Millimeter fan compared, to the 80mm fan that your old power supply has.

A larger fan means it will run quieter, due to the fact that it won't have to turn as fast, in order to put out as much air.
Will actually put out more air than that 80mm fan, and will spin slower.

3) Has two 12 Volt power rails.
One 12 Volt rail can deliver 17 Amps.
The other 12 Volt rail can deliver 14 Amps.

You can add the two 12 Volt power rail Amp's together, for 31 Amps.

Means less strain for the power supply, to keep up with the tasks.
(Your old power supply probably has an 18 Amp, 12 Volt power rail)

4) Has all the power cables you'll need.

5) Price, and reliable quality.

This is one place that carries them,

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=4675269&CatId=1078

There are other places also. Not advertising for the above website, nor the power supply manufacturer.
Just my personal preference, based on experience with both.

A computer only uses the power it needs, and NO more.
If you install a 1000 Watt power supply in your computer, and the computer only needs 100 Watts, it only uses 100 Watts.

(Surfing the internet typically uses 100 Watts of power. Like a 100 Watt light bulb)

This may help guide you in replacing the power supply,

http://www.hardwaresecrets.com/article/362

I found out that the AT supply SA145-3435 does not have a switch wire like an ATX supply. I have a SA145-3435 my self. To get it to work it must have a +5 volt load (BLACK and RED) and a +12 volt load (BLACK and YELLOW). If it does not have both of these loads it will power down after a 2 second delay when you plug it up. I used 2 small 12 volt bulbs. One for the 12 volt line and one for the 5 volt line. The type of blub I used was a #94 I got from the auto parts store.