Skip to main content

Seasonic Focus Plus Gold 850 PSU Review

Teardown & Component Analysis

Parts Description

Before proceeding with this page we strongly encourage you to a look at our PSUs 101 article, which provides valuable information about PSUs and their operation, allowing you to better understand the components we're about to discuss. Our main tools for disassembling PSUs are a Thermaltronics soldering and rework station and a Hakko FR-300 desoldering gun. Finally, for the identification of tiny parts we use an Andonstar HDMI digital microscope.

General Data
Manufacturer (OEM)Seasonic
Platform ModelFX
Primary Side
Transient Filter4x Y caps, 2x X caps, 2x CM chokes, 1x MOV, 1x CM02X
Inrush ProtectionNTC Thermistor & Relay
Bridge Rectifier(s)2x GBU1506 (600V, 15A)
APFC MOSFETs2x Infineon IPW50R190CE (550V, 15.7A @ 100°C, 0.19Ω)
APFC Boost Diode1x STMicroelectronics STTH8S06D (600V, 8A @ 125°C)
Hold-up Cap(s)1x Nippon Chemi-Con (400V, 650uF, 2000h @ 105°C, CE)
Main Switchers4x UTC GPT13N50DG (500V, 13A @ 100°C, 0.49Ω)
APFC ControllerChampion CM6500UNX
Resonant ControllerChampion CM6901T6X
TopologyPrimary side: Full-Bridge & LLC Resonant Controller Secondary side: Synchronous Rectification & DC-DC converters
Secondary Side
+12V MOSFETs4x Nexperia PSMN2R6-40YS (40V, 100A @ 25°C, 2.8mΩ)
5V & 3.3VDC-DC Converters: 6x Infineon BSC0906NS (30V, 40A @ 100°C, 4.5mΩ) PWM Controller: APW7159
Filtering CapacitorsElectrolytics: Chemi-Con (1-5000 @ 105°C, KZE), Chemi-Con (4-10,000 @ 105°C, KY), W Polymers: Chemi-Con
Supervisor ICWeltrend WT7527V (OVP, UVP, OCP, SCP, PG)
Fan ModelHong Hua HA1225H12F-Z (120mm, 12V, 0.58A, 2200 RPM, Fluid Dynamic Bearing)
5VSB Circuit
Standby PWM ControllerExcelliance EM8569
Image 1 of 4

Image 2 of 4

Image 3 of 4

Image 4 of 4

This platform is exactly the same as the one we saw in Seasonic's Focus Plus Gold 750. It's a new design featuring a full-bridge topology on the primary side, along with an LLC resonant converter. We find typical stuff on the secondary side: a synchronous design for the +12V rail and a couple of DC-DC converters for the minor rails. Unfortunately, the -12V rail is regulated through a plain diode and not a proper regulator, which would provide increased reliability and safety against overloading. The filtering caps come from Chemi-Con; some of them are special-order from Seasonic, since we can't find any information about them. The cooling fan only measures 120mm across, since a larger one wouldn't fit in this compact chassis.

Image 1 of 7

Image 2 of 7

Image 3 of 7

Image 4 of 7

Image 5 of 7

Image 6 of 7

Image 7 of 7

The first part of the transient filter is on a small PCB located right behind the AC receptacle. A couple of Y caps and a single X cap are there, along with a CM02X that blocks current through the X cap discharge resistor when AC voltage is connected. The same IC also automatically discharges the X cap through the discharge resistor when AC is disconnected. Seasonic's EMI filter continues on the main PCB with two more Y caps and a single X one, two CM chokes, and an MOV. It's an effective filter, given the low conducted EMI transmissions we measured.

An NTC thermistor protects against large inrush currents; it is supported by a bypass relay.

Image 1 of 2

Image 2 of 2

A couple of bridge rectifiers (GBU1506) are bolted onto a dedicated heat sink.

Image 1 of 2

Image 2 of 2

The APFC converter uses two Infineon IPW50R190CE FETs and a STMicroelectronics STTH8S06D boost diode. The bulk cap is provided by Chemi-Con and it has a capacity of 650uF. We measured a longer than 17ms hold-up time (the ATX spec's minimum), so the bulk cap clearly has enough capacity for this platform.

Image 1 of 2

Image 2 of 2

The APFC controller is installed on the main PCB's solder side, along with the LLC resonant controller. The first is a Champion CM6500UNX, while the second is the omnipresent CM6901.

Image 1 of 2

Image 2 of 2

The primary FETs are four UTC GBT10N50ADGs (the same ones in Seasonic's SSR-750FX) configured in a full bridge topology. An LLC resonant converter is also used for boosting the unit's efficiency.

On the secondary side, the +12V rail is rectified by four Nexperia PSMN2R6-40YSes. Exactly the same configuration is used in Seasonic's SSR-750FX. So far, the main difference between its 850W and 750W Focus Plus Gold units are the APFC FETs.

Image 1 of 4

Image 2 of 4

Image 3 of 4

Image 4 of 4

Chemi-Con filtering caps on the secondary side belong to the company's KZE, KY, and W lines. Besides electrolytic caps, a few polymer Chemi-Con caps are also used for filtering purposes.

A couple of DC-DC converters are located on small vertical PCB, employing six Infineon BSC0906NS FETs and a single ANPEC APW7159 PWM controller.

The supervisor IC is a Weltrend WT7527V. This IC supports OCP at +12V for up to two channels. However, this PSU sports a single +12V rail. The same IC supports all important protection features except for OTP, which is implemented through another circuit.

The standby PWM controller is a Excelliance EM8569 IC.

Image 1 of 5

Image 2 of 5

Image 3 of 5

Image 4 of 5

Image 5 of 5

On the front of the modular board, four polymer caps and four electrolytic caps, all provided by Chemi-Con, further suppress ripple.

Image 1 of 6

Image 2 of 6

Image 3 of 6

Image 4 of 6

Image 5 of 6

Image 6 of 6

Seasonic's soldering quality is pretty good, although some of the component leads could be shorter.

Image 1 of 2

Image 2 of 2

The fan is made by Hong Hua and its model number is HA1225H12F-Z. It features an FDB bearing and can rotate at high speeds if needed. This power supply does employ a relaxed fan profile, so you'll have to push it pretty hard under high ambient temperatures to make the fan run at full-speed. At that point, it generates about 45 dB(A) from one meter away.


MORE: Best Power Supplies


MORE: How We Test Power Supplies


MORE: All Power Supply Content

  • JohnnyLucky
    Nice review. I'll add it to the psu recommendation list I maintain.

    Last week newegg had the 650 watt model on sale for $74.99. There was a $20.00 mail-in rebate which brought the price down to $54.99. On top of that there was a free $30.00 gift certificate for a fresh food vendor online which my wife wasted no time in using. That brought the final price down to $24.99. Best deal I've taken advantage of this year.
    Reply
  • JohnUSA
    I just found this model selling for just $74 at SuperBiiz-dot-com, which I think is a great deal.
    Reply
  • buzznut47
    This was rated highly by JonnyGuru, and based on that I made a purchase 2 or 3 months ago. I have been mostly happy with its performance. I am running an FX 8320 @3.8 Ghz, 2 R9 280X, custom loop with 8 fans, and a couple of drives.

    Initially I was really impressed that there was so much power in such a small package. Until I saw the cables, and the ridiculous capacitors. I know this brings a fantastic level of ripple, but I don't like it at all.
    I gotta say, I really don't like this trend with higher end power supplies. As a modder, my cables are visible. And these cables would be satisfactory, if the capacitors were located ON THE PSU SIDE!! But they are located on the component side where they can be seen in all their glorious ugliness. It is not recommended to change the polarity..
    I will be checking the units I buy more carefully moving forward. I would much rather have a longer power supply unit that has the caps inside.

    Bottom line though, it is a gold 850W unit at an affordable price and a 10 year warranty. For efficient cards like the RX570/580 and GTX 1060, there are enough cables for 6 video cards. Pretty good for mining, but as for a visible gaming rig I have to say 4 out of 5 stars for functionality. Just put the caps at the other end of the cable, ya big dummy.
    Reply
  • berezini
    Still haven't changed my mind on getting one after killing my new motherboard and couple other components. Just would never recommend seasonic ever again.
    Reply
  • ZRace
    Great review, looks like this will be my next PSU unless something better releases by the time I need a replacement. Definitely gonna recommend this to others!
    Reply
  • JohnnyLucky
    ARIS - Are you still here?

    The PCIe cables are a little different than what I am used to. The 850 model and my 650 watt version have PCIe cables with two connectors instead of just one at their device end. Does that mean one PCIe cable can be used for both connections on a graphics card? On the other hand do I still have to use two PCIe cables and let one connector on each cable just hang there?

    Anybody else know?
    Reply
  • Leaps-from-Shadows
    20427267 said:
    Still haven't changed my mind on getting one after killing my new motherboard and couple other components. Just would never recommend seasonic ever again.
    Even the best manufacturers produce the occasional lemon. It's too bad you're one-and-done -- you're really missing out on quite possibly the best power supplies out there.

    It's okay though ... they will survive without your money.
    Reply
  • Leaps-from-Shadows
    20430290 said:
    ARIS - Are you still here?

    The PCIe cables are a little different than what I am used to. The 850 model and my 650 watt version have PCIe cables with two connectors instead of just one at their device end. Does that mean one PCIe cable can be used for both connections on a graphics card? On the other hand do I still have to use two PCIe cables and let one connector on each cable just hang there?

    Anybody else know?
    You can certainly use the two connectors from a single cable. However, a video from JayzTwoCents showed it was better to use two separate cables.
    Reply
  • JohnnyLucky
    Leaps - Thanks for the info.

    I went back and read the review. In the specs it shows 3 PCI-e cables and 6 connectors. It also indicates the 3 cables could be used with 3 video cards, each requiring 2 connectors.

    I'll take a look at the video. I've watched some of his other clips.

    Don't know how I missed this development.

    Reply
  • Leaps-from-Shadows
    20430533 said:
    Leaps - Thanks for the info.

    I went back and read the review. In the specs it shows 3 PCI-e cables and 6 connectors. It also indicates the 3 cables could be used with 3 video cards, each requiring 2 connectors.

    I'll take a look at the video. I've watched some of his other clips.

    Don't know how I missed this development.
    Here it is, in case you couldn't find it...
    Reply