HP Z800 PSU repairs, anyone?

Discussion in 'DIY Server and Workstation Builds' started by BLinux, Oct 16, 2017.

  1. BLinux

    BLinux cat lover server enthusiast

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    Earlier this year, I got a HP Z800 workstation computer for dirt cheap, $250 or so, off eBay. It's a pretty well configured machine, 2x X5675, 48GB, etc. It was purchased for my 3rd grader son to play, learn, and do homework on. It's worked great until about 2 weeks ago, where it now randomly resets or shuts off. Searching online, this seems to be a common problem with HP Z800 power supplies; some claim bad capacitors. I'm not shy of doing such repairs myself, but in this case, I tore apart the PSU and found no visual signs to indicate which capacitors may have gone bad, or if it even is a capacitor issue. The PSU tests fine in standalone, but when there's a load, *sometimes* it shuts off, or cycles between on and off repeatedly. There's a clicking sound, sort of like a relay, and my guess is that it's some protection circuit that is flipping the relay.

    I'm wondering if there might be other STH members here familiar with this issue that I can discuss this with? I tried to throw money at this problem, but ended up with a used PSU off eBay that was in worse shape. I figure if I can fix the PSU with high quality components, that might be a longer term fix.

    Anyone?
     
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  2. Twist

    Twist Member

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    Capacitors can be defective even if they don't show any unusual visual signs - to check them you have to use an esr meter.

    Take some quality photos of unit and make a thread in 'Power Supply Design and Troubleshooting' over at Badcaps, several users usually give very good help over there.
     
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  3. BLinux

    BLinux cat lover server enthusiast

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    Yup, ESR meter is my next purchase at this point. And yes, I realize caps can fail with no visual signs; just mentioning that this one isn't as simple as visual inspection. I'm hoping the ESR will help me identify which cap has gone bad, but although they mention in-circuit, I assume I should desolder at least one leg in case there are caps in parallel?

    Thanks for that... didn't really know about that site.
     
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  4. Twist

    Twist Member

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    I bought the ESR micro v4, the guy who builds them is a member on Badcaps and if I remember correctly you will get a discount if your a member. I usually lift them of board, I use a Hakko FR300 so it's easy and fast.

    It's a good forum, some of the users have high understanding and can give you lots of tips.
     
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  5. wildpig1234

    wildpig1234 Well-Known Member

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    yeah doesn't look like cheap psu either. they run like $100+
     
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  6. Sameer

    Sameer New Member

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    Hi, I kinda has the exact same issue here. The issue is that i can't just buy a new Power Supply as they are all used and they cost + shipping almost half as much as i paid for the Workstation itself.
    I know this post is old but i thought to give it a shot and ask.

    Rally appreciate any help here. P.S. I'm not even sure its the PSU so pointing in that direction is a great help
     
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  7. BLinux

    BLinux cat lover server enthusiast

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    unfortunately, the options were not great for me. the 1st replacement PSU i got from eBay was bad out of the box. I returned it and got myself a ESR meter. I tried to use the ESR to see if I could find the bad component in the PSU and replace it, but I could not find what was wrong with it. I had a friend who's been electronics repairs most of his life take a look at it, and he couldn't pinpoint the problem either. Meanwhile, I found another PSU on eBay for about $70 that had a slightly newer revision number, so I gave that a try and that has so far been stable. This PSU problem seems to be very widespread for HP Z800 machines, and I found many other people with the same problem. Some of them were able to pinpoint their problem to a failing capacitor on 5VSB, but I don't think that was the problem in my case.
     
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