The el-cheapo power supply round-up

Besta PT-500

Those of you who knew me before Hardware Insights existed may remember that I once did a more basic review on an identical unit to this. To cut a long story short, it turned out to be more of a “worsta”. It’s voltage regulation was poor and it exploded long before we hit the the labelled rating. Now that I have a bit of extra testing equipment, and another unit, why not include it as part of this roundup?


The fact that a new unit still has more current on the 5v rail than on the 12v shows that whoever designed this unit must still be using old Socket A based computers. That was the last socket where more than 30A on the 5v rail was required. Nowadays, it’s the 12v rail where the current needs to be.

Load Testing

Test 1 (120.76W Load – Cold)

Rail Load Voltage Ripple
12V 4.9A 12.24V 33.7mV
5V 5.12A 5.12V 14.4mV
3.3V 10.24A 3.38V 20.0mV
−12V 0A −12.15V 10.0mV
5Vsb 0A 5.13V 5.62mV
AC Power 147.6W
Efficiency 81.82%
Power Factor 0.62


Test 2 (212.9W Load – Cold)

Rail Load Voltage Ripple
12V 9.72A 12.15V 45.6mV
5V 10.18A 5.09V 19.4mV
3.3V 10.45A 3.45V 31.3mV
−12V 0.1A −12.23V 24.4mV
5Vsb 1.01A 5.03V 48.8mV
AC Power 248.9W
Efficiency 85.29%
Power Factor 0.6


Test 3 (237.02W Load – Cold)

Rail Load Voltage Ripple
12V 12.02A 12.02V 51.3mV
5V 10.16A 5.08V 16.9mV
3.3V 10.24A 3.38V 30.0mV
−12V 0.1A −12.33V 22.5mV
5Vsb 1A 5.02V 40.6mV
AC Power 282W
Efficiency 84.05%
Power Factor 0.59

Test 4 (291.08W Load – Cold)

Rail Load Voltage Ripple
12V 14.48A 12.07V 56.3mV
5V 15.09A 5.03V 13.1mV
3.3V 10.15A 3.35V 31.3mV
−12V 0.11A −12.70V 26.9mV
5Vsb 1A 5.00V 60.6mV
AC Power 345.7W
Efficiency 84.20%
Power Factor 0.6

Test 5 (348.38W Load – Cold)

Rail Load Voltage Ripple
12V 14.48A 11.88V 65.6mV
5V 15.18A 5.06V 31.9mV
3.3V 20.24A 3.34V 29.4mV
−12V 0.11A −12.91V 26.3mV
5Vsb 1A 4.99V 81.9mV
AC Power 419.52W
Efficiency 83.04%
Power Factor 0.6


This unit actually performed quite well for a cheaper power supply. The voltages did actually stay within spec and the efficiency was above 80% the whole time. The ripple was in check too until we hit test 4 at about 290W. The ripple on the 5vsb then went out of spec. During test 5 at about 350W, the unit failed shortly after I finished reading all of the parameters. It didn’t explode like my last PT-500. It just shut down and wouldn’t start up again.


Rail Test 4 (291.08W) Test 5 (348.38W)

A look inside


It’s pretty much identical internally to my last Besta PT-500. The input filtering is mostly there, although it still needs an extra coil and an MOV. It also has a 4A bridge rectifier, rather than the 4 individual diodes commonly used in cheaper units. Unfortunately, though, the two primary capacitors are only 470μF parts from an obscure manufacturer called QMLCON. I couldn’t identify the manufacturer or find a datasheet for the switching transistors either. The part number printed on them is simply “13007”, which is a generic part number used by several manufacturers, so it really doesn’t tell us anything. Like the other 7 power supplies in this round up, the PT-500 uses a dated half bridge design.

Bolted to the secondary heat sink, the output rectifiers used are two MOSPEC F12C20C fast recovery rectifiers for the 12v rail. This gives a total of 24A on the 12v rail. It’s more than enough to do what the label says, but it would have been better to use a Schottky rectifier, since they offer better efficiency and thus they don’t heat up as much and I might not have burned my fingers from touching the heat sink. The 5v rail has a single STPS3045CW Schottky rectifier rated at 30A, which is not enough for the 37A on the label. The rectifier on the 3.3v rail looks to be from the same manufacturer as the primary switching transistors, which I couldn’t identify. The part number is simply “20S45”, which suggests it’s a 20A part. Again, it’s insufficient for the 28A rating. The capacitors on the secondary side are all BH, which are of questionable quality.


The fan has no branding on it, nor does it have a UL number, so it’s another part I can’t identify the manufacturer of. That said, I’ve seen that logo on a few other fans before and and most of them were seized up or really noisy, so it’s unlikely to be a high quality part. The PT-500 lacks a fan controller, so the fan just runs at its maximum rated speed regardless of the temperature. However, the unit was still fairly quiet, so the fan is probably a low speed model.

Actual specifications

Real Wattage 290W
OEM Unknown
PFC None
Price $30 (AUD)
ATX Connector type 20+4 pin
Worst-case voltage regulation (12v, 5v, 3.3v) 2%, 2.4%, 4.5%
Worst-case ripple (12v, 5v, 3.3v) 65.6mV, 31.9mV, 31.3mV
Worst-case efficiency 81.82%
Input filtering Inadequate
CPU Connector ATX12v (4 pin)
PCIe Connectors None
Molex (Peripheral) Connectors 4
FDD Power connectors 1
SATA Power connectors 1


Pros: Voltage Regulation, Efficiency

Cons: Couldn’t deliver 500W, Inadequate Input filtering, Only 1 SATA connector, Low quality fan and capacitors, No PFC, More current available on 5V rail than on 12V rail

Bottom Line: The performance was good for a cheap unit, but it doesn’t have enough connectors, can’t deliver 500W and uses low-quality parts.

Score: 4/10

Right, let’s move on to our next victim, and see if we can get better results or better fireworks.

Pages: 1 2 3 4 5 6 7 8 9 10 11