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Old 09-12-2014, 10:19 AM
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mushy409 mushy409 is offline
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Join Date: Sep 2014
Location: Sheffield
Posts: 15
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Hey Rsnubje - thanks for your reply.

Yes I've replaced the coil (R47), the top gate driver (CHL8510) and 2 MOSFETs that it controls. This phase seems to be ok, voltage readings from both hi/low side are good.

Spent a few hours this afternoon butchering a PC motherboard to reclaim a PCIe socket so I can test the card outside the PC. The adaptor works great (thanks TiN!)
At least this way I can probe both sides of the board with my scope.

I've been VERY careful with this card - no tracks have been cut/modified and the only soldering I have done was removing those FETs and driver with a hot air wand & preheater.

What I'm stuck on at the moment is whether the gate drivers are toast (CHL8510) or the actual PWM controller as the PWM signal for each phase differs. I traced the PWM signals back to the CHL8228 and tested at the IC - still the same readings as there are no passive components on the PWM line.

One thing I have noticed is that now 4 of the phases don't seem to be working correctly and when I probe the MODE pin on the CHL8510 (pin 8) of these phases I can hear a faint "click" and the PWM kicks into protection mode by switching off ALL of the phases (reading is 0.1v)

I'm 100000% positive nothing was shorted as I'm using a needle point probe with only 1-2mm of tip showing to prevent any shorts, and also a magnifier to see where I'm at.

If I probe pin 8 of the top (far right in the pic) CHL8510 and also the bottom (far left) this pin reads voltage and the PWM continues to run.
If I probe any in between then the PWM shuts down...

Again, faulty PWM controller or faulty CHL8510? I'm not sure...

I don't want to start pulling out parts just yet, neither do I want to rush into buying more components without being sure. Plus the fact what I've spent so far on the card & parts I could have bought an EVGA Epower card and just have done with the borked VRM circuit.

Damn I wish I finished my A-level electronics! Practical knowledge is great, the theory & maths behind it is another!
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