CompUSA PowMax LP-6100 – this is as good as they get!
Ah, good ol' PowMax! I mean, who doesn't love them, right? 
Even Topcat himself used to "frequently recommend and use Powmax supplies"
Don't believe me? Have a look here.
(P.S. Sorry TC, I just had to make a funny here. Hope you don't mind.
)
Anyways, folks.
What I will be showing you today is a CompUSA 500 Watt power supply based on the Leadman/PowMax LP-6100 platform. For those of you who are still scratching your head and wondering about Leadman/PowMax – it's basically a company that used to (and still does?) make some of the worst power supplies ever. Therefore, their PowMax is often called POW to the MAX here… and for a good reason
. I think you might have gotten a hint of that even in the above link.
That said, the LP-6100 platform/design is probably the closest they ever came to almost making a half-decent PSU, in my opinion. (Note my careful wording in that last sentence. ) I say that, because the guts of the LP-6100 visually don't look all that terrible. Yet, there are plenty of stories of PowMax PSUs blowing up, including this model.
Now let's see some pictures of my model. As usual, I always start with the case/shell and label.
https://www.badcaps.net/forum/attach...1&d=1451693563
https://www.badcaps.net/forum/attach...1&d=1451693563
As you can see, this CompUSA "500 Watt" PSU is a dual-fan design: one pushing air in and one pulling air out of the PSU, both wired in parallel to the same temperature controller. Both fans are made by Yate Loon (FM802512H and FM802012H, rated for 0.18 and 0.19 Amps, respectively.) Now this may sound surprising, but the case metal is actually of proper thickness and doesn't feel flimsy at all. In fact, it feels very sturdy. Even with the guts removed, the case still feels heavy. You can also see from the pictures that the output wires are quite long and not so thin like on other cheap PSUs. In fact, they are all rated for 300V, 18 AWG and have legit UL numbers. In terms of connectors, this one has a 20-pin ATX, 4-pin CPU, 6-pin AUX (AT style), six standard drive connectors, and two Berg floppy drive connectors. So, on the outside, this does actually look like a decent PSU. And it has some weight to it, too.
Moving onto the label:
https://www.badcaps.net/forum/attach...1&d=1451693563
We see 40 Amps on the 5 V rail and 30 Amps on the 3.3 V rail?! That's 1 Watt short of 300 for the 5 V and 3.3 V rails combined. A bit overrated? I think so! After all, how else are the numbers on the label going to add up to the promised rating of 500 Watts?
Another interesting bit is Leadman/PowMax's UL number (E107407). Nothing comes up in the UL database if you look it up. I guess it could be expired. Or it could be forged. Either way, don't let that comfort you that this is a perfectly safe PSU, because it probably isn't.
And now, time for the guts:
https://www.badcaps.net/forum/attach...1&d=1451693563
Clearly, you can see why this PSU has weight to it. There are good-sized heatsinks and full input filtering. Also note the proper-spec primary wires (18 AWG, 600V). The small board on the secondary heatsink is the fan controller. Again, everything looks decent so far.
Well, let's see the solder side:
https://www.badcaps.net/forum/attach...1&d=1451693563
I'm not impressed here. :\ The soldering is not terrible, but still sloppy in a few places. I didn't measure the creep distance between primary and secondary, but I think it is 5 mm for the most part. The only thing I am not sure about is the solder: it seems too dull to be Pb (Leaded) solder but too shiny for Pb-free.
Finally, we take a look at the secondary side:
https://www.badcaps.net/forum/attach...1&d=1451693563
https://www.badcaps.net/forum/attach...1&d=1451693563
Now you see why I stopped using this PSU! – Bulged Jun Fu caps at their finest. They lasted maybe 3 years of light-moderate use with a low-power 5 V-based PC (AMD Duron 1400 Applebred CPU and Radeon 9200 SE) – possibly even less than 3000 hours, based on the counter in my Maxtor 32049H2 hard drive. Unacceptable!
Those bad caps aside, the secondary side doesn't look that bad either. Each major rail has two caps and space for a PI coil. Only the 5 VSB and 3.3 V rails are missing their PI coils. Also note the huge output toroid inductors – the size of the 3.3 V rail toroid is actually what you would find as the *main* output toroid inductor in cheap PSUs. And the main output toroid inductor on this PSU is huge. It has very thick wires, too: three for the 5V rail, two for the 12V rail, and one for the -12V rail. Good job, PowMax! At least you didn't cut corners there.
But this is a PowMax PSU after all, so there has to be something wrong with it.
https://www.badcaps.net/forum/attach...1&d=1451693563
It may not seem like anything, until you look carefully. At the lower left side of this picture, there are two jumpers. Between them is connected the leg of ceramic cap C17. The reason I pick on this is because the two jumpers are directly connected to the 5 V rail, whereas the leg of C17 that goes between them is connected to ground underneath. If the ceramic insulation breaks away (and it easily can from a physical disturbance), there will be a hard short-circuit from the 5 V rail to ground. And if that happens, let's hope this PSU has proper short-circuit protection. Otherwise, it will likely live up to it's name
The primary-side RCD snubber network (seen to the right of the transformer) is another point of concern, in my opinion. The big diode (FR307) you see is actually not part of this RCD snubber network. Instead, it is a snubber for an additional winding on the primary side of the transformer, which is something I have never seen in STF topologies from good manufacturers, like HiPro, Delta, and Lite-ON. Why PowMax has designed it this way rather than a more standard method is beyond my understanding. And given that I have seen pictures of blown primary sides of this PSU before, I wouldn't be surprised if marginal snubber design has something to do with it. As for the actual RCD snubber network, there is a second (small) diode underneath the big diode. I believe it is an FR107 (1 A, 1000 V). It is connected in series with a 22 KOhm 2 (or 3) Watt resistor parallel with a 100 nF 400V metalized polypropylene cap. To me, that 22-KOhm resistor seems a bit too high to keep the inductive kickback of the primary in check (though, I will admit I haven't measured it). The primary MOSFET is rated for 600V max only.
Finally, we have a look at the 5 VSB section:
https://www.badcaps.net/forum/attach...1&d=1451693563
Again, we see more disappointments here. First off, this *is* a 2-transistor design *with* a "critical" cap (25 V, 47 uF, spot C32). The 5 VSB transformer is very tiny. According to everell, that transformer runs hot even with just 5 Watts load (1 Amp at 5 Volts) after a few minutes. Another thing to note is that the 5 VSB primary side drive transistor (a 2SK3067 MOSFET) is not heatsinked at all! The PCB area underneath its pins is slightly darkened in my unit, so I definitely think it needs one. The snubber RCD network is nearly the same as for the main PS, except the snubber cap is only a 10 nF ceramic rather than 100 nF polypropylene. So I am not sure how good that is. But I suppose it's good enough for the 5 VSB rail.
Here is a schematic of the 5 VSB circuit that I drew:
https://www.badcaps.net/forum/attach...1&d=1451693563
The last thing to mention about the 5 VSB circuit is that the primary side auxiliary winding is also used for providing power to the PWM controller. The secondary side of the transformer has only one winding – the 5 Volt output. It is used both for the 5 VSB and powering the supervisory IC. The PCB has spots for components so that the supervisory IC can have its own filtered output. However, PowMax went cheap here and connected the supervisory IC Vcc directly to the 5 VSB output through a diode rather than installing all of those components.
Anyways, that is all for the 5 VSB section. I haven't ran any load tests on it like I did with some of my other PSUs (since the primary caps are currently removed).
Even Topcat himself used to "frequently recommend and use Powmax supplies"
Don't believe me? Have a look here.
(P.S. Sorry TC, I just had to make a funny here. Hope you don't mind.
)Anyways, folks.
What I will be showing you today is a CompUSA 500 Watt power supply based on the Leadman/PowMax LP-6100 platform. For those of you who are still scratching your head and wondering about Leadman/PowMax – it's basically a company that used to (and still does?) make some of the worst power supplies ever. Therefore, their PowMax is often called POW to the MAX here… and for a good reason
. I think you might have gotten a hint of that even in the above link.That said, the LP-6100 platform/design is probably the closest they ever came to almost making a half-decent PSU, in my opinion. (Note my careful wording in that last sentence.
) I say that, because the guts of the LP-6100 visually don't look all that terrible. Yet, there are plenty of stories of PowMax PSUs blowing up, including this model. Now let's see some pictures of my model. As usual, I always start with the case/shell and label.
https://www.badcaps.net/forum/attach...1&d=1451693563
https://www.badcaps.net/forum/attach...1&d=1451693563
As you can see, this CompUSA "500 Watt" PSU is a dual-fan design: one pushing air in and one pulling air out of the PSU, both wired in parallel to the same temperature controller. Both fans are made by Yate Loon (FM802512H and FM802012H, rated for 0.18 and 0.19 Amps, respectively.) Now this may sound surprising, but the case metal is actually of proper thickness and doesn't feel flimsy at all. In fact, it feels very sturdy. Even with the guts removed, the case still feels heavy. You can also see from the pictures that the output wires are quite long and not so thin like on other cheap PSUs. In fact, they are all rated for 300V, 18 AWG and have legit UL numbers. In terms of connectors, this one has a 20-pin ATX, 4-pin CPU, 6-pin AUX (AT style), six standard drive connectors, and two Berg floppy drive connectors. So, on the outside, this does actually look like a decent PSU. And it has some weight to it, too.
Moving onto the label:
https://www.badcaps.net/forum/attach...1&d=1451693563
We see 40 Amps on the 5 V rail and 30 Amps on the 3.3 V rail?! That's 1 Watt short of 300 for the 5 V and 3.3 V rails combined. A bit overrated? I think so! After all, how else are the numbers on the label going to add up to the promised rating of 500 Watts?
Another interesting bit is Leadman/PowMax's UL number (E107407). Nothing comes up in the UL database if you look it up. I guess it could be expired. Or it could be forged. Either way, don't let that comfort you that this is a perfectly safe PSU, because it probably isn't.
And now, time for the guts:
https://www.badcaps.net/forum/attach...1&d=1451693563
Clearly, you can see why this PSU has weight to it. There are good-sized heatsinks and full input filtering. Also note the proper-spec primary wires (18 AWG, 600V). The small board on the secondary heatsink is the fan controller. Again, everything looks decent so far.
Well, let's see the solder side:
https://www.badcaps.net/forum/attach...1&d=1451693563
I'm not impressed here. :\ The soldering is not terrible, but still sloppy in a few places. I didn't measure the creep distance between primary and secondary, but I think it is 5 mm for the most part. The only thing I am not sure about is the solder: it seems too dull to be Pb (Leaded) solder but too shiny for Pb-free.
Finally, we take a look at the secondary side:
https://www.badcaps.net/forum/attach...1&d=1451693563
https://www.badcaps.net/forum/attach...1&d=1451693563
Now you see why I stopped using this PSU! – Bulged Jun Fu caps at their finest. They lasted maybe 3 years of light-moderate use with a low-power 5 V-based PC (AMD Duron 1400 Applebred CPU and Radeon 9200 SE) – possibly even less than 3000 hours, based on the counter in my Maxtor 32049H2 hard drive. Unacceptable!
Those bad caps aside, the secondary side doesn't look that bad either. Each major rail has two caps and space for a PI coil. Only the 5 VSB and 3.3 V rails are missing their PI coils. Also note the huge output toroid inductors – the size of the 3.3 V rail toroid is actually what you would find as the *main* output toroid inductor in cheap PSUs. And the main output toroid inductor on this PSU is huge. It has very thick wires, too: three for the 5V rail, two for the 12V rail, and one for the -12V rail. Good job, PowMax! At least you didn't cut corners there.
But this is a PowMax PSU after all, so there has to be something wrong with it.
https://www.badcaps.net/forum/attach...1&d=1451693563
It may not seem like anything, until you look carefully. At the lower left side of this picture, there are two jumpers. Between them is connected the leg of ceramic cap C17. The reason I pick on this is because the two jumpers are directly connected to the 5 V rail, whereas the leg of C17 that goes between them is connected to ground underneath. If the ceramic insulation breaks away (and it easily can from a physical disturbance), there will be a hard short-circuit from the 5 V rail to ground. And if that happens, let's hope this PSU has proper short-circuit protection. Otherwise, it will likely live up to it's name
The primary-side RCD snubber network (seen to the right of the transformer) is another point of concern, in my opinion. The big diode (FR307) you see is actually not part of this RCD snubber network. Instead, it is a snubber for an additional winding on the primary side of the transformer, which is something I have never seen in STF topologies from good manufacturers, like HiPro, Delta, and Lite-ON. Why PowMax has designed it this way rather than a more standard method is beyond my understanding. And given that I have seen pictures of blown primary sides of this PSU before, I wouldn't be surprised if marginal snubber design has something to do with it. As for the actual RCD snubber network, there is a second (small) diode underneath the big diode. I believe it is an FR107 (1 A, 1000 V). It is connected in series with a 22 KOhm 2 (or 3) Watt resistor parallel with a 100 nF 400V metalized polypropylene cap. To me, that 22-KOhm resistor seems a bit too high to keep the inductive kickback of the primary in check (though, I will admit I haven't measured it). The primary MOSFET is rated for 600V max only.
Finally, we have a look at the 5 VSB section:
https://www.badcaps.net/forum/attach...1&d=1451693563
Again, we see more disappointments here. First off, this *is* a 2-transistor design *with* a "critical" cap (25 V, 47 uF, spot C32). The 5 VSB transformer is very tiny. According to everell, that transformer runs hot even with just 5 Watts load (1 Amp at 5 Volts) after a few minutes. Another thing to note is that the 5 VSB primary side drive transistor (a 2SK3067 MOSFET) is not heatsinked at all! The PCB area underneath its pins is slightly darkened in my unit, so I definitely think it needs one. The snubber RCD network is nearly the same as for the main PS, except the snubber cap is only a 10 nF ceramic rather than 100 nF polypropylene. So I am not sure how good that is. But I suppose it's good enough for the 5 VSB rail.
Here is a schematic of the 5 VSB circuit that I drew:
https://www.badcaps.net/forum/attach...1&d=1451693563
The last thing to mention about the 5 VSB circuit is that the primary side auxiliary winding is also used for providing power to the PWM controller. The secondary side of the transformer has only one winding – the 5 Volt output. It is used both for the 5 VSB and powering the supervisory IC. The PCB has spots for components so that the supervisory IC can have its own filtered output. However, PowMax went cheap here and connected the supervisory IC Vcc directly to the 5 VSB output through a diode rather than installing all of those components.
Anyways, that is all for the 5 VSB section. I haven't ran any load tests on it like I did with some of my other PSUs (since the primary caps are currently removed).
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