RE: Einsy-Rambo 1.2e Exploded component
Hey everybody, thanks a lot for the help.
I haven't had much time to get into it so sorry for the delay.
Using this image:
While trying to solder the wire to C124 - 2, I heated the later of the C124 and it peeled off whole. And I ran into what you see in picture A, should I clean the base to expose the copper channels?
As it seemed that the point C124 - 2 could not be soldered, I tried with the C124 - 1 and it did not work at all (if I later realized that it is normal that it did not work since it is the line of pin 2).
I have the C124 kept to try to put it back in place.
And looking at the diagram and how is the PCB diagram I am seeing well each part according to this?
I understand that if the point C124-2 can not be used I should go to another clean point to look for the current, right?
At this point how should I proceed?
(Note: I have noticed testing that if I use the tester in continuity mode, if I put between pin 1 and pin 2 of FAN 1 of this PCB gives me 0.99 and 1.08, and the same for PCB 2, but on PCB 2 in the FAN 0 gives me 1.30-1.50, the question is if in the same places I change the resistance value this mark 1 (equivalent to that does not measure anything), how should I understand these values of “continuity”.
One more, what does the C124 itself do? I mean I have looked on the internet that it stores electricity but I do not understand what does it do there? (Maybe it is a very silly or obvious question but I do not know).
RE: Einsy-Rambo 1.2e Exploded component
As you write, C124 acts as a local buffer of electricity. If the current consumption of the fan changes rapidly (on microsecond timescales) or if it sends little voltage spikes back into the system, C124 provides those short peaks of extra current or absorbs the voltage spikes.
It is good practice to provide such capacitors between the supply voltage and ground of active components (like ICs) throughout the PCB, "just for good measure", and you will probably see many more in the schematic. 100 nF is a typical value for this purpose. But in most cases, the circuit will work OK without these capacitors. For a first test, I would just leave C124 out of the circuit.
You are right -- if you can't solder the wire to the terminal of C124, you can move "upstream" to the next connection point. The connection between LED5 and transistor Q2A would be your next opportunity. But be careful not to damage the PCB or components there. Do you have a temperature-controlled soldering iron meant for electronics work? C124 and its solder pads may still have been overly sensitive due to their overheating when FB40 burned through, but it might also have been your soldering iron running too hot which caused C124 to detach.
[Not sure how much soldering practice you have. Just in case: The trick is to first place the wire in the right position, touching the intended joint. (Use a "third hand" with a movable crocodile clip or such to position it in a stable way, or have another person help using a pair of pliers. Don't hold that wire in your fingers since it will get hot...) Then briefly heat up the wire and PCB pad at the same time with your soldering iron; 1 to 2 seconds are enough for small parts. Then, while still holding the iron in place, touch your solder onto the hot joint. It should flow right away and smoothly adhere to the wire and pad. Remove solder and iron; done. Do not melt solder on the iron first, then touch the wire and joint with it; it will no longer flow since the flux will already have boiled away. -- Apologies if you already know and do all this!]
Finally, the observed difference between continuity mode and resistance mode is indeed a bit unexpected. And I am not sure what value your multimeter displays in continuity mode. Is it possible that you had set "diode testing" mode instead and that it was displaying the diode's forward voltage? COuld you share the brand and model number of your multimeter?
RE: Einsy-Rambo 1.2e Exploded component
With no ferrite core and no C124 and no fan connected, the resistance between pin one and pin two should be infinite. There is no connection to provide any continuity. Any resistance measured is due to the circuit board contamination.
When PCBs are manufactured, there are coatings (solder mask) put onto the circuit boards to prevent solder from going places that it isn't not supposed to go. Residue from burnt circuit boards, being mostly carbon is also a hindrance to getting solder to adhere and it is also conductive. Some types of resistors are made with carbon.
It is why I suggested to clean the board before proceeding. It is what I do first, remove all traces of carbon before I even think of testing or repairing a board. It will be hard to solder to any connection if you don't see bright copper and without a decent solder or solder and flux. Flux is a form of solvent that helps remove the oxidization on the copper. Be careful not to use a flux that isn't designed for electronics. It can destroy the circuit board. I have made that mistake.
Looking at your image, I suspect the power to the pin is fed by the two vias that are left of the green square on image C. Vias are connections between the layers of the circuit board. If I am correct, then you need to be connected to those two points. If I was doing this repair, I would clean the copper on those two points, lay a piece of wire and solder it to the copper trace next to the fan pin. Bend the wire down and make sure it is contacting both of the vias coming through the circuit board, then solder at that point. You cleaned the copper close to pin 1 and that is where I would solder one end of the wire.
As Jürgen said, you have to be careful about the amount of heat applied to the circuit board. Heat damages the bonding of the copper to the board material and makes it easier to lift off. Once they start lifting, it is time to be careful, and attempt to minimize damage. As Jürgen said, you can use things like a "third hand" to hold wires where you want them. You can glue the wires down to the circuit board where you want them, before soldering. You glue at the insulation or the wire, not where you put the solder.
One note of importance. Some lead free solders have a very narrow operating temperature range. The soldering iron needs to be within that range for the solder to work. You need to know that recommended temperature for the solder you are using and set your iron to be close to that temperature.