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Author Topic: Successfully fixing Radeon HD 5850 with burnt capacitors  (Read 2371 times)
goxed
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October 20, 2012, 08:40:30 PM
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Hope it helps someone, may even work for other HD5xxx cards.

My Radeon 5850 took the dive!
Two decoupling capacitors at the back of the board were literally glowing red and were burnt out, por que AMD!

The card was showing up in windows, and drivers loaded correctly. Could not run cgminer, as the system would just become unresponsive with dead screen.

Anyways after removing the heatsink, I realised that two phases of the VRM were dead and not just the decoupling capacitors, but two 0.01Ohm Chip resistors feeding the +ve rail of the VRM phases were dead as well.

So here are the parts that I replaced / fixed (Access to parts with 'I', need the heatsink to be removed)

Ia) MR524 0.01Ohm replaced with 2 thin strands of copper wire
Ib) R527 replaced with 2 thin strands of copper wire
Oc) C510, C520, replaced with chip capacitors  (should tolerate 12V or more)
Od) C527, C529, replaced with chip capacitors (should tolerate 12V or more)

You can easily find donor devices for the chip capacitors such as DSL modems, Cooling fans, dead PSU, etc. Make sure it's rated for 12V.

Here is link to inside pic


Here is link to outside pic
http://i.imgur.com/k7MRJh.jpg

I did a hasty job (was planning to ebay the card), and didn't have liquid flux, so the soldering job was a bit shoddy, but it can be more elegant.

Looking to review Bitcoin / Crypto mining Hardware.
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kuusj98
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October 20, 2012, 09:19:28 PM
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wow, thats some nice work you did there Cheesy Does it work normally now?
goxed
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October 20, 2012, 09:21:44 PM
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wow, thats some nice work you did there Cheesy Does it work normally now?

Thanks! Yes! it's mining away since last one hour now Smiley

Looking to review Bitcoin / Crypto mining Hardware.
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October 21, 2012, 02:19:26 AM
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What kinda testing did you do to ensure that the caps were the only problem...and what caused the burnt caps? Plus I think you got lucky in just replacing the caps.
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October 21, 2012, 02:33:39 AM
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What kinda testing did you do to ensure that the caps were the only problem...and what caused the burnt caps? Plus I think you got lucky in just replacing the caps.

As I mentioned the capacitors were glowing red due to heat! and subsequently burnt out. It's called looking at the obvious symptoms first. Using a DMM, the measured resistance across the chip caps was ~ 5Ohms. Obviously caps are supposed to block DC, not conduct Wink

Here take a look at this thread, it's a common problem with reference 5850. My guess is that the caps are faulty, and they produce a short circuit after many hours of usage.
https://bitcointalk.org/index.php?topic=101624.0

I not only replaced the caps but two 0.01Ohm resistors feeding the rails, as well, since the caps had shorted out and subsequently the resistors had burnt out as well.

Looking to review Bitcoin / Crypto mining Hardware.
nick0016
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October 21, 2012, 06:36:19 AM
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Nice work!

So, it's better to give my 5850 some rest every day? Wink

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