Hey guys,
Been trying to self repair my laptop that has recently bit the dust, it's a Tongfang board model number gk7cp6s (commonly sold by XMG, Schenker, Mechrevo, Eluktronics).
my initial tests to find the fault I connected one of my multimeter leads to ground, and started testing capacitors at random, and found out that some of the capacitors around the CPU were shorting to ground on both ends.
I got myself a voltage injection tool, and I started injecting about 1.8 volts onto the shorting cap, and found that the CPU was heating up under the thermal cam, so I suspected that the problem was the CPU.
I took the CPU under a heat gun to gently heat it up, removed the CPU then tested for a short, and the short was gone, but when I soldered on the new CPU, the short came back and I'm really at a loss as to what's going on right now.
Does anyone have any ideas?
Capacitors near the CPU or GPU tend to have very low resistance and it's normal for the meter to beep in Continuity or Diode when testing.
Ohm Readings on those caps can be as low as 0.2 ohms. Injecting voltage directly to a low resistance line will most certainly heat up the CPU. It does not mean the CPU is shorted or bad. You'll need to test the Vcore circuit assuming that is the problem, check for bad mosfets or caps if any and replace as needed. If after replacing a faulty component, the board is still not powering on or CPU not behaving normally as far as heat properties goes, then it's may be that you have a dead CPU that was killed by high voltage entering thru a faulty component linking directly. Assuming the new CPU is good to begin with and it was soldered on properly and was not killed by injecting 1.8v direct, Look elsewhere. Start with 0.8v-1.2 when injecting voltage. You may not know the value of every component on the board and what should read what, but you build that up over time when you have a similar working board that you can test and compare values to. That's how you build your experience. Best of luck
@alex Thanks for the reply Alex, your help is greatly appreciated, I always enjoy following your videos.
If the laptop still charges fine (light comes on orange when battery isn't full, and turns yellow when it's full), in your experience, what could you think the issue is?
by my deductions and testing, the charging port seems fine, if the battery is being charged just fine, then I assume that the charging IC is fully working, together with the two MOSFETs that are beside the charging port.
I'm a little stumped as nothing seems to visually look damaged (no burn marks, no visibly damaged components).
Again, thanks a lot for your help
I noticed that this Diode was shorting to ground on both ends, and so I removed it to test the diode, but the diode seems fine, but both the pads are still shorting to ground.
@hamsteyr That's not a diode, that's a capacitor.
And as Alex said, the caps around the CPU will read as short.