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Thread: DEEPCOOL DQ 850-M-V2L & CWT GPX

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    Quote Originally Posted by awesomegamer919 View Post
    Isnt the GBU806 an 8A rectifier? You have it listed as 10A
    You are correct. Copy and paste error (which is how I made this table). Fixed.

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    Well, that's kinda worrying to hear. How often do 115V mains go down to <100V for a time that is required to blow up those FETs?

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    @Jon Gerow

    I'm worried because I see some half-bridge PSUs with the same SVF13N50F MOSFETs you mention, like Corsair CX450 (CWT) or Bitfenix Formula 450W. Do they work well there because they're only 450W PSUs? Or do they have problems as well? What am I missing here? And for example Bitfenix Whisper 550W, which uses a different model from Silan (2x SVF20N50F(500V, 12.6A @ 100C, 0.27Ohm)). Should we have special concerns with any of them?

    Thanks!

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    Quote Originally Posted by Jon Gerow View Post
    I have two dead GPX PSUs here. Both of them had Q2 explode when the mains was dropped to <100V. Typically, the bridge rectifier will die because it's undersized or may fry after a while because there's no heatsink. But not these guys! As soon as we hit <100V.... BLAM! They blew up. Even if spec is 100V-240V, a PSU shouldn't blow up. It should at least turn off.

    At full load?

    Q2 is a main switching transistor? or PFC control

    a few details seem to have been left out
    Last edited by ashiekh; 07-10-2020 at 11:10 AM.

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    450W and 850W are totally different story. The much lower current and the resulting much lower temperature mean considerable less stress.

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    Quote Originally Posted by breixobaloca View Post
    @Jon Gerow

    I'm worried because I see some half-bridge PSUs with the same SVF13N50F MOSFETs you mention, like Corsair CX450 (CWT) or Bitfenix Formula 450W. Do they work well there because they're only 450W PSUs? Or do they have problems as well? What am I missing here? And for example Bitfenix Whisper 550W, which uses a different model from Silan (2x SVF20N50F(500V, 12.6A @ 100C, 0.27Ohm)). Should we have special concerns with any of them?

    Thanks!
    Quote Originally Posted by Philipus II View Post
    450W and 850W are totally different story. The much lower current and the resulting much lower temperature mean considerable less stress.
    Like Philipus said. Totally different wattages. So yes, the "problem" could be solved with a beefer current rating for 650W, but then you're losing some of your cost savings.

    I will admit that the CX needed to have the heatsink beefed up while in EVT because we were blowing those FETs up as well.

    I'll post the other wattages when I have a chance. Problem is, the data is spread across multiple documents and I have to copy and paste them into a single sheet to have them side by side.
    Last edited by Jon Gerow; 07-10-2020 at 01:21 PM.

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    Quote Originally Posted by ashiekh View Post
    At full load?

    Q2 is a main switching transistor? or PFC control

    a few details seem to have been left out
    PWM. I only mention PFC because usually that goes out in low voltage conditions when they're anemic. I was quite surprised when Q2 blew. Now I have to read this: https://www.onsemi.com/pub/Collateral/AN-9067.pdf.pdf

    But that's what's weird, right? PWM should be working at bus voltage. So why would the PWM FET blow if mains voltage is low??? So weird. Or maybe it's just a coincidence and it just overheated because the adjacent PFC circuit was running hotter due to the low mains voltage. That's a thought.

    Quote Originally Posted by efficient View Post
    Well, that's kinda worrying to hear. How often do 115V mains go down to <100V for a time that is required to blow up those FETs?
    Japan is 100V, BTW.

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    Just a thought... if the voltage is down, the main transformer may get saturated (the modulation trying to compensate) and short the transistor? One could watch the voltage on the bulk capacitor as the mains voltage sinks; I assume you are using a variac to control the mains voltage.

    Another bad guess?


    I'm so far out of my depth, my conjecture is no longer useful.
    Last edited by ashiekh; 07-10-2020 at 04:09 PM.

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    Quote Originally Posted by ashiekh View Post
    Just a thought... if the voltage is down, the main transformer may get saturated (the modulation trying to compensate) and short the transistor? One could watch the voltage on the bulk capacitor as the mains voltage sinks; I assume you are using a variac to control the mains voltage.
    Of course not. We're using a Chroma 61505.

    But good thought on monitoring the bus voltage. Need to get another unit first, though.

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    Why another unit? just get a box of identical power transistors, and some that are superior; replacing the whole unit limits testing. Are there separate fly-back diodes and if so, did they survive?
    Last edited by ashiekh; 07-10-2020 at 06:27 PM.

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