ModdIt
Not knowing what has already been done, a pretty general and surely improvable set of fault finding tips, apply in kind to desktops computers phones powerbanks chargers
and vehicle components.
Power supplies: BE CAREFUL, the big caps are deadly. Safest is do not open a PSU, if you must, discharge the caps and short them with a resistor which you then solder
over the terminals to be sure no residual charge sends you to your grave.
Start with different power source, running all the time from the brick max stresses it, high temperatures dry out caps giving unstable working in particular at start.
Have seen problems with the cable being badly connected to plug, at device end it gets a lot of stress. Usual fix is replace power brick.
Check socket to board connection, In a good shop in Hannover they are resoldered on suspicion when accessible.
Check all capacitors near power supply connector for any signs of bulging or leakage, I use 8x magnifier since finding a pinhole sized defect in a capacitor top. That
was in a monitor PSU but any electrolytic caps can be affected.
Remove RAM clean off contacts with iso alcohol and reseat it. If more than one socket is in use sometimes a system runs stable with one piece inserted. Is a common shop
check. Seems when the chips and sucomponents get old timing can drift off to borderline.
Check screen connection, both the connector and look for signs of any damage where the cable goes from case to screen in hinge area. Very common to find issues there
especialy on devices which have had screen replacement in past.
Then if you want to dig deeper it gets dirty, Carefully check for any signs of hairy or fluffy looking solder joints as well as any discoloration or corrosion.
The hairy joints are due whiskers growing out of the solder, they can and do cause short circuits or partial short circuits between contacts, the effects range
widely, from weird symptoms to component destruction.
Early lead free soldered boards aged very badly. Any suspects clean with isipropanol destilled water dry and resolder where possible.
Tap or lightly press on chips using an insulated probe. That often helps where faulty early lead free solder is involved. Intent is find cracked solder joints
which are often extremely hard to see, Shop uses a stereo camera setup and a big screen, maybe a digicam on a tripod live connection and monitor could imitate
that, possibly some kinds of action cam too, distortion does not rally matter, just clear detail of connections.
you can use a cold spray and shock cool chips, that if done carefully can aid in diagnostics, it can also finish a chip where
the internal layer contacts are faulty.
Louis Rossman Videos are well worth watching for tips including on soldering resoldering fault finding , many on youtube are on an extremely amateur level, he is not.