sourcerer wrote:
I did some research into GPU repair lately, and there is one thing that I definitely learnt from that field: Always check for shorts before turning it on. How to check for shorts? Well, that is surprisingly simple: You take a multi-meter, put it into resistance mode, and measure the resistance of the device that you want to test on the power pins / power connector. If the resistance is too low, then you have a short and you will most likely get the magic smoke when you turn it on.
For SATA disks you check the SATA power pins (one pin of your multimeter to the SATA ground pin, and another pin of your multimeter to SATA +5V pin. SATA provides 3 different power levels, +3V, +5V, +12V so you should check all 3 different power level pins.
As a reference, on the Samsung EVO840, the +3.3V on pin 1 gives 7.9 MegaOhm, the +5V on pin 8 gives 9MegaOhm and the +12V on pin 15 gives infinite resistance, which means that it is not connected.
If you measure a resistance of less than 10 Ohm, you most likely have a short and should fix the short before applying power to it.
You can apply the same procedure to nearly every device, from hair driers to refridgerators to mainboards, ... which you get and you aren't sure whether they are OK or not. Just measure the resistance.
The only exception I have come across yet are GPUs , the GPU chips actually have a very low resistance so for them, measuring 0.9 Ohm of resistance on the power rails can be OK, so you need for them you need more knowledge on the expected resistances of the GPU chips to decide whether they are OK or not. For everything else, <10 Ohm should be a usable rule.
Since I learnt about the resistance measurement a few months ago, I applied to to many different devices and successfully identified shorts in devices before they went up in smoke. Therefore I highly recommend that you check the resistances on every customer disk you get before powering it up. This way you can save them from bigger damage.
What you have highlighted makes sense.
Infact even while repairing audio power amps, studio gear (analog compressors, eqs, preamps, audio monitors etc etc) this trick is always handy
1)a transformer at primary in such cases will always be DC shorted
2)Post rectifier, pre regulators and post regulators this trick works neatly even in the above-mentioned cases of audio gear.
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