Hey all,
a Repair Cafe has opened right next door and as I got some basic experience with electronics and I’m pretty good at soldering I thought I’d go there and help fixing stuff. BUT I’m very bad at diagnosing stuff and this is where I turn towards you. I would like to know how to diagnose a circuit and how to get it working without necessarily having a schematic or anything to work with on the device.
So currently my order of inspection is, aside from common sense trouble shooting like cleaning contacts:
Visible inspection for damage and corroded stuff on the board -> if there is some, remove corrosion, try to wire up / replace damaged stuff
Check for power supply, is there voltage coming out of it that does sound reasonable? -> if no pretty much dead end for me but I at least know that it has to be at least partly the fault of the power supply
Check for cold or ripped solder points or try knocking on the board at various places while having power on the device to locate cold solder points -> totally fixable if found
Some examples for the last meetups:
Navigation Device: Broken Micro USB Socket -> fixed with new USB Socket soldered in
Smartphone: Does turn on, display stays black with a little bit of static noise, has been dropped into water but there is no water damage like corrosion visible on the board, display is correctly supplied with current but does only display static -> give up due to lack of entry point for potentially resoldering bad connections
DVD Player: Always reports „no disc“ -> cleaned laser, oiled up motor, checked power supply and it worked, probably the oil creeping into the motor at that time and lubricating it enough to drop the resistance low enough again to correctly spin up the disc
Yamaha Amplifier: Has a loose connection somewhere obviously, toggles on/off when knocked on the case. After some knocking on the mainboard to locate the fault it went dead completely, I resoldered almost all of the points but it still didn’t work. Probably a broken trace somewhere, but no idea how to track that
Smartphone: Only has left ear audio output, cleaned up the port but it didn’t get much better, resoldered the port but still no improvement. -> no further idea of tracking the cause of the fault
As you can see we get a lot of mixed stuff and considering the stuff is dead on arrival a success rate of around 50% overall is not that bad, but I feel I could do better if I could track down the issues better. With some I got a pretty good idea what could be doable. With others there is just not much I can think of to track down the issue. So I would be very glad for hints or tricks about tracking generic home appliances or mobile stuff for errors that might not be visible at first look.
As for me, I do know basic electrical stuff. I can recognize basic components and I know most of the components on a board by sight, I also can recognize some basic stuff like bridge rectifiers. So I’m not completely lost, but I’ve got very basic electrical knowledge when it comes to more advanced stuff. Which is partly why I’m participating too so I can learn.