As I mentioned in my previous post, I had a power supply fan fail in one of my Dell Optiplex 755 systems. Although I received a replacement supply from Dell (the system is under warranty for another two years) I decided to look into a larger power supply, as I’d upgraded the hard drive, CPU, and video card. The standard Dell supply is only 305 watts and I expect it is running near its rated capacity.

I’ve been using PC Power & Cooling products since the company was founded – the first product I used was a fan that bolted onto the back of an IBM PC XT to improve airflow. I haven’t used their products recently, as the few systems I’ve built from scratch have come with power supplies already installed in the cases.

I took a look at their site and found the Silencer 500 Dell power supply which stated that it was a direct replacement for the Dell power supply in my Optiplex 755. It also said it was a direct replacement in 61 other Dell systems, which should have given me a clue that the unit was more generic than it was letting on.

This power supply slightly exceeds the efficiency rating of the stock Dell power supply (82% vs. 80%) while providing up to 500 watts continuous power.

I unpacked the power supply, which came in a nice printed box (my earlier PCP&C supplies had come in generic brown cardboard boxes, which indicates how far power supplies have come in being recognized as a critical component of the system). There was a huge wad of cables coming out of the supply – far more than the Optiplex 755 needed.

I did a test fit of the supply in the chassis and discovered that there were a number of problems. First, the AC power cord connector interfered with part of the case. Next, the case had tabs which were designed to slot into the Dell power supply. The PCP&C supply was lacking those slots, so it was impossible to mount the supply perfectly squarely in the case.

The first change I made was to modify the AC power cord connector on the supply so it would fit in the case. This involved cutting off the plastic “ear” on one side of the connector. Fortunately there is a metal tab on the connector which will help retain it once the power supply is installed in the chassis:

Next, I had to come up with a plan to deal with all the unused power cables:

My first idea was to tie them up neatly in the space between the power supply and the back of the DVD drives:

However, it was a very tight fit and it severely reduced the airflow through the power supply, as the vents on the inside face of the supply were nearly completely obscured by the mass of cables.

As I had already voided the warranty by trimming the power connector, I decided to open the supply and remove all of the un-needed cables. I could have cut them off outside the supply, but then I would have to individually insulate all of the cut ends and it would be really ugly.

After a brief round of cutting, the excess cables were removed:

As part of this process, I removed the floppy drive power connector (mini 4-pin) and installed it on the end of one of the SATA power cable branches. As supplied by PCP&C, the floppy connector is at the very end of a long chain of full-size 4-pin connectors (used for legacy hard drives and CD-ROMs, of which this system had none). I trimmed one of the SATA power cable branches to 2 SATA power connectors and installed the floppy connector at the end. I also removed the last connector from the other SATA power cable branch, leaving 2 connectors, and routed it down to the hard drive bay in the system. This produced a set of cables that was far more manageable:

I don’t recommend doing this yourself – aside from voiding the warranty, you could easily damage the power supply or injure yourself. PCP&C says that they don’t believe in power supplies with modular cable systems (see FAQ #3 here). However, as long as they are going to continue to represent the supply as fitting 62 different Dell models, they need to come up with some system to deal with un-needed cables. Also, it is important to remember that there are already a pair of connectors on each cable – one on the cable end and the other on the device it is plugged into. PCP&C has no control over those connector styles as they’re dictated by industry standards. But they would have unlimited choices for modular power connectors if they decided to use them.

Also, while they could justify the cables by saying that they don’t know what cards and peripherals a customer might have, there is no excuse for the interference of the power connector with the PC case – this is clearly a case (no pun intended) of someone looking at the specs of the Dell power supply and saying “sure, ours will fit” without ever checking it for themselves. It should be possible to move the power connector closer to the center of the power supply without requiring a complete re-design of the power supply and without imparing the fitment in the other Dell cases. PCP&C offers custom power supplies, but I shudder to think what the cost would be for a one-off solution to the problems I encountered.

While I’m satisfied with the solution I came up with, I can’t recommend this supply for use in the Optiplex 755 (due to the power connector mounting issue) or in any other space-limited Dell enclosure (because of the large number of un-needed cables).

This entry was posted on Friday, February 6th, 2009 at 9:42 pm and is filed under Computers. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.