Compatible Power Supply Unit to Replace Original in Old System

[Petros_k]

(Note: This system is not being used for gaming.)

I've got an old Compaq EVO D310. Original power supply unit:
model: DPS-250RB A
220 Watts
20 PIN (motherboard connector)
1 x 4-Pin CPU Power Connection
4 x 4-Pin Molex
2 x Floppy Disk Driver Power Connection
+3.3V@15A, +5V@11A, +12V@5A, +12.8V@7.5A, -12V@0.15A, +5VSB@3A
Motherboard parts diagram is here: http://bizsupport.austin.hp.com/bc/d.../c00571576.pdf


I want to replace it with this:
model: HEC 350W Power Supply - 80+ Bronze (HEC-350TA-2RK)
350 Watts
1 x 20
1 x 4-Pin Main Connector
2 x 4-Pin Molex
1 x Floppy
4 x SATA
+3.3V@21A, +5V@15A, +12V1@14A, +12V2@14A, -12V@0.3A, +5VSB@2.5A


Three Questions:

1. When replacing a power supply unit, if the new unit says it has a 20-pin connector for the motherboard, will all 20-pin connectors fit the same way?

2. Not sure what the specs that say, e.g., +3.3V@15A vs +3.3@21A. Is this more or less about efficiency?

3. Unit size: These are both labeled as ATX form factor, but I'm not sure if the HEC power supply unit is the right size for the original EVO D310 case. Are all ATX units the same size? What do I do if the new unit doesn't quite fit?

 

[Harvey]

Three Questions:

1. When replacing a power supply unit, if the new unit says it has a 20-pin connector for the motherboard, will all 20-pin connectors fit the same way?

2. Not sure what the specs that say, e.g., +3.3V@15A vs +3.3@21A. Is this more or less about efficiency?

3. Unit size: These are both labeled as ATX form factor, but I'm not sure if the HEC power supply unit is the right size for the original EVO D310 case. Are all ATX units the same size? What do I do if the new unit doesn't quite fit?

Three answers:

1. Yes, the 20 pin connector is a standard. Newer motherboards require a 24 pin connector. Most newer PSU's have either the standard 20 pin connector and a separate 4 pin connector that fits beside it, or a 24 pin connector that can be split to 20 pin connector and a 4 pin connector that isn't used on 20 pin motherboards.

2. The current rating in amperes (A) is not an efficiency spec. It specifies the maximum current the PSU can provide at the specified voltage. More is better, especially since the PSU's in most "department store" computer brands are undersized for the job. Way more just means the PSU is over-qualified for the job. However, replacing the original 220 watt PSU with one rated at 350 watts is a good idea.

3. "ATX form factor" is an industry standard for size and mounting centers, although there are some supplies that are smaller with mounting holes to fit into an ATX case. If you have any questions, you can check the specs on Newegg's product page for this HEC PSU.

Dimensions: 5.9" x 5.51" x 3.39"

This PSU has only two 4 pin Molex connectors so, if you need to power more than two devices that use them (hard drive, CD/DVD drive, etc.), you'll need a power splitter adapter like this one from frys.com.

Hope that helps.

 

[Petros_k]

Thank you for the reply.

If I need more than 2 Molex type connectors, can't I also get adapters to fit the SATA connectors to convert them?

 

[Harvey]

If I need more than 2 Molex type connectors, can't I also get adapters to fit the SATA connectors to convert them?

Possibly, but the most common adapter looks like this:

Note that the most common 4 pin Molex to SATA adaptor has a male Molex connector, the same as your drives. You would need a similar adapter with a SATA to female Molex connector, which is not as common.

The more typical adapters are widely available and cheap. You may be working too hard and over-thinking the problem.

 

[Petros_k]

Note that the most common 4 pin Molex to SATA adaptor has a male Molex connector, the same as your drives. You would need a similar adapter with a SATA to female Molex connector, which is not as common.

The more typical adapters are widely available and cheap. You may be working too hard and over-thinking the problem.

Nothing new there! I'm just trying to cover all my bases.

But if I can ask you one more thing, somebody at another forum is telling me that HEC is a terrible brand and that I shouldn't buy the unit mentioned above no matter how cheap it is. I realize it's not going to be a top of the line power supply unit, but is it really not going to get me an upgrade from the original PSU?

 

[Harvey]

But if I can ask you one more thing, somebody at another forum is telling me that HEC is a terrible brand and that I shouldn't buy the unit mentioned above no matter how cheap it is. I realize it's not going to be a top of the line power supply unit, but is it really not going to get me an upgrade from the original PSU?

I've heard that, as well, so since you're now looking at other options, here are a couple of places to start looking:

Here's a selection of PSU's from Newegg listed by price up to 450 watts. You can go through them and use the check boxes on the left to narrow your search for special features like 80+ certification, etc. Once you have a list of possible units, check reviews for each of those that interest you.

Frys.com has a couple of PSU's that may interest you:

Antec Earthwatts EA-430 Green PSU 430w ATX Power Supply
$44.00
80 PLUS® Bronze certified

Thermaltake TR2 430W ATX 12V 2.2 Power Supply W0070RUC
$39.99
Not 80+ certified.

Of the two, I've had good experiences with both Antec and Thermaltake supplies, but I'd go for the 80+ cert just to feel good about doing something green. That said, do your homework on these and any other specific model you consider.

A side thought is that the basic quality of a supply comes when it's running under its maximum spec'd power. A basically sound PSU that isn't top tier, but is rated FAR above your anticipated demand will probably hold together quite well. For example, a supply rated at 350 watts won't come under stress if the maximum your system demands is only 220 watts.
Hope that helps.

 

[VirtualLarry]

I've got an old Compaq EVO D310. Original power supply unit:
model: DPS-250RB A
220 Watts
+3.3V@15A, +5V@11A, +12V@5A, +12.8V@7.5A, -12V@0.15A, +5VSB@3A
Motherboard parts diagram is here: http://bizsupport.austin.hp.com/bc/d.../c00571576.pdf

Are you absolutely certain that there is both a +12V and a +12.8V rail? If so, I'm afraid what you have is non-standard, and you may have to search for an exact replacement. (eBay)

 

[Petros_k]

Are you absolutely certain that there is both a +12V and a +12.8V rail? If so, I'm afraid what you have is non-standard, and you may have to search for an exact replacement. (eBay)

These are the numbers on the label for the unit, which you can see for yourself here:

http://www.atlantisgadgets.com/index.php?main_page=product_info&cPath=5_10&products_id=100

There's both a +12V and a +12.8 listed (last one at the bottom).

Why is this not compatible with the HEC unit listed above?

There is absolutely no point in replacing the original power supply unit (DPS-250RB A) with the same model, and no need to, because mine is working fine. I am trying to UPGRADE it to 300 - 350 watts because I'm installing a video card (only a GeForce FX 5500 which is low watt and needs about 25 watts only at PEAK performance. It's not for gaming purposes), and I may be at the limit of what the original 220 watt unit is capable of providing to all the installed devices. However, I have been told by some people that if I'm disabling the original Intel 82845G graphics controller I may not need to upgrade the power supply unit only for a video card that doesn't draw more than 25 watts. Others disagree and say I'm already maxed out. I was thinking it wouldn't hurt to have a little more power available. Now I've got a reason to be concerned I shouldn't mess with the original power supply unit?

 

[Petros_k]

Consider what someone at another website says about the +12.8V rail: "I'm fairly certain this PSU was for a P4 board and the +12.8 VDC rail was on the 20+4 or 20+6 connector as the Vcpu pins. Looking at some of the older manuals on Manual Libs, shows that this is likely correct"

He's provided a small diagram: http://superuser.com/questions/587739/what-is-the-12-8v-rail-on-my-psu

If it's true that this specific voltage is for the 20-pin connector and the CPU power supply (Pentium 4 CPU, 2.40 GHz), it's best not to mess with it?

Also someone here http://forums.hardwaresecrets.com/showthread.php?threadid=4392 also noticed this about a Compaq power supply unit and is asking the same Q:

"Any chance the MOBO actually NEEDS oddball voltages like:
5.08v, 3.33v, 12.8v..."

Someone responds saying: "Yes manufacturers have/do make changes to make their parts proprietary. You may need a Compaq power supply. "

Regarding the form factor of the original PSU, he's also saying the Compaq "minitower" (I believe used with both my model, which is an EVO D300 series, along with the D500 series) is not really ATX compatible. There are some pics of the case included.

Interesting, the post at the above forum is from 2009, and the guy is saying the Compaq power supply is built better than some of the 4-500 watt power supply units he's seen.


I'm starting to think this is one of those issues where if it ain't broken, don't try to fix it.

 

[Petros_k]

In fact, maybe I should backup for a minute...

The primary reason I was thinking it might be a good idea to upgrade the original 220 watt power supply unit is that I want to disable the original Intel 82845G integrated graphics controller, which is WAY out-dated (along with the rest of the system I guess) and install a low watt video card in the available 4x AGP slot : a GeForce FX 5500, which does not draw more than 25 watts when at its PEAK performance.

So, I was introduced to a power supply estimator tool here: http://extreme.outervision.com/psucalculatorlite.jsp

The estimator tool recommends 50 watts headroom above the total required for all devices installed. The power supply estimator also assumes you are running all installed devices at the same time, which I questioned. Someone told me that there is one time that all installed devices run at the same time, which is at start up. He said when you power on a computer, anything with a motor (like a hard drive) requires 3X the recommended watts. I was concerned now that I should be adding up what's installed in my system to see if I might be in trouble if I install the video card.

When I used the estimator tool to add up what my system was CURRENTLY running, I got a recommended power supply unit that exceeded the 220 watts of the original unit.

Basic system:
2.4 GHz Pentium 4 CPU (Socket 478, Northwood, estimated watts below used CPU at 90% TDP)
1 IDE hard drive 7200RPM
1 DVD/CD-R combo optical drive
2 sticks DDR RAM
3-80mm fans
(My modem is externally powered, so I'm not including it.)

152 watts required / 202 watts recommended.

I considered that the above doesn't include that a hard drive motor needs three times its estimated running power when it starts up and needed to add 36 more watts. So now, the required power for the above to run at startup is 188 watts (152 + 36). With the recommended headroom applied to this (50 watts) the estimator tool would recommend 238 watts -- larger than the original power supply unit.

But the above listed devices are not all that are running on my system. I've got another IDE 7200 RPM hard drive. So now, we should be adding another 54 to the total required watts if it needs 3x the required power for startup (18 watts normal running + 36 more for start up). That puts the total required watts at 242 watts and I'm only running the 220 watt OEM Compaq unit.

But additionally, I have a PCI soundcard installed. The estimator tool uses 13 watts as the average wattage needed for a PCI card. Tack on the watts for my soundcard and I should require 255 watts. The estimator tool would add 50 watts headroom to this. So now, the recommended power supply unit should be 305 watts. Yet, somehow, I'm running these devices using the 220 watt power supply unit that came with the computer.

So, you can see why I'm concerned about the apparent "need" for a new power supply unit, but I have questions about 1) why the power supply is estimated in such a way that assumes all installed devices are running at the same time, and 2) if I didn't include the power needed for the Intel 82845G integrated graphics controller originally installed on the MOBO, which I intend to disable, I may not need much more power if all I'm installing is an AGP video card like the GeForce FX 5500.

When it came to my attention that a 350 watt power supply unit was available for not much money (the HEC-350TA-2RK noted at the first post above), I figured it wouldn't hurt to add some available watts to the system, or so I thought. NOW, it looks like I opened up a can of worms.




I tried to do what I think is a more conservative estimate of my power supply requirements. The basic system requirements are still the same, 152 watts.

add 2nd hd drive (+ 18 watts, not including the 3X factor for startup):

170 watts total required

add a PCI soundcard (+ 13 watts, average)

183 watts total required

If all the above devices were running at maximum power requirements for a sustained period they would need 183 watts. My power supply unit can handle a maximum of 220 watts, so the demand would not be greater than what's available. I left out the existing Intel 82845G graphics controller, but it's not important because it's going to be disabled. If you now add a Nvidia FX 5500 video card (+ 25 watts at peak performance) you get:

208 watts total

If this is accurate, I still have 12 watts available from my 220 watt psu for a very modest headroom, but again, the estimate assumes all these devices are running at the same time and maximum power is required from the system. It is highly unlikely that this will ever occur, unless it's true that when powering on the computer you need to have much more headroom than 12 watts because all the devices start up at the same time. I'm also being told that power supply units are made to be able to withstand a brief surge of maybe 50-100 watts higher than the rated watts for this purpose, so it's still unclear to me what I actually "need."

Someone suggested I get one of those "Kill-A-Watt" meters that you plug appliances into to see how much power it draws and I'd know what my system is doing. The meter is $22 -- the cost of some power supply units!

If I can't get a straight answer about this 12.8V rail issue regarding the original power supply unit, and given it may be crucial to run the motherboard and CPU with the 20-pin connection, I may just try installing the GeForce FX 5500 AGP video card without changing the original power supply. I was also thinking I could disable my second hard drive (which is only used for backup) while trying to see how the system works with the video card installed to see if the power supply unit stalls or if the system keeps rebooting. Of course, I've already been told that if the original PSU starts smoking or shorts out suddenly it could take other components with it, including the CPU. Hence, my concern for getting a new power supply unit. Funny how all I want to do is install a video card that needs about 25 watts max and all these other issues are involved!

Keep in mind that someone else suggested if the motherboard for my system has 3 PCI slots and an AGP slot the power supply unit should be able to run devices installed there. Why would they include the slots on the motherboard with no upgraded power supply available made by Compaq or HP (there is no other power supply that I know of to fit in the EVO series except for a 240 watt model in the D500 series)? There was also a video card that HP offered as an after-market upgrade to run on the 220V power supply, a NVIDIA GeForce2 MX200 64-MB with DVI-I output. I'm sure they didn't expect users to need to upgrade the power supply unit to run it, but I do not know how many watts it needed.