A Look Inside & Component Analysis

Before reading this page, we strongly suggest a look at this article, which will help you understand the internal components of a PSU much better. Our main tool for the disassembly of the PSU is a Thermaltronics TMT-9000S soldering and rework station. It is of extreme quality and is equipped with a matching de-soldering gun. With such equipment in hand, breaking apart every PSU is like a walk in the park!


The manufacturer of this unit and of all L8 units, modular and non-modular, is HEC/Compucase. A company with a tradition in low cost PSUs that has lately improved their budget platforms a lot, offering much better performance and fixing the ripple suppression problems that haunted their older products. The L8-500W uses a group regulated design in the secondary side along with passive components to rectify the DC outputs. There is nothing too fancy in the primary side either as it doesn't takes cutting-edge technology to achieve Bronze efficiency.


The transient filtering stage starts at a small PCB located behind the AC socket. There, one X and two Y caps along with a CM choke are installed. The second stage of the transient filter is installed on the main PCB and consists of two CM chokes, two Y caps, a single X one, and an MOV (Metal Oxide Varistor) that offers protection against surges coming from the mains network.


The single bridge rectifier is a GBU10J. It can handle up to 10 A of current and is bolted to a dedicated heatsink.


In the APFC section, two MDF18N50 fets along with a BYC8-600 boost diode are used to shape the input current sinusoidal. The bulk cap is provided by Teapo (400 V, 270 μF, 85°C, LH series) and is rather small for the needs of this unit. Also, the voltage rating of this cap is low and close to the DC bus of the APFC circuit (~380 VDC). Ideally, a 420 V or even better a 450 V cap should be used but it is significantly more expensive, so most manufacturers prefer 400 V ones. The latter case requires a tight tolerance in the feedback/reference voltage of the PFC controller to ensure that in the cap will not take voltage beyond its rating.


The main switchers are two MDF18N50 fets and the combo PFC/PWM controller is a Champion CM6800TX IC.


The standby PWM controller is a TNY279PN IC by Power Integrations. This IC incorporates a 700V power MOSFET to handle the 5VSB output.


We, as you can see, had to remove the main transformer to provide you with a clear view of the components installed on the secondary heatsink. Two pairs of PFR30L45CT and 40U60CT SBRs handle the +12V and 5V rails. The 3.3V rail is generated by two STPS30L45CT SBRs. Finally, a group regulation scheme is used in the secondary side for the generation of all rails, which won't allow for good performance with highly unbalanced loads on the rails.


All caps in the secondary side are provided by Teapo and are rated at 105°C. We couldn't ask for a better caps choice in a budget unit since the Japanese ones are much more expensive, and Teapo caps are probably the best Chinese caps.


The protections IC, a Weltrend WT7527 IC that supports OCP for up to two +12V rails, is soldered to the component side of the main PCB.


With clean and good looking solder joints, soldering quality on the main PCB is just fine.


The cooling fan is Be Quiet's design and uses special blades that increase airflow and decrease output noise levels. Its model number is BQT T12025-MS-16 (12 V, 0.2 A, 1600 RPM, rifle bearing, 25.1 dBA max). It is generally a really quiet fan at even high speeds.