I have a controller for an electric throw blanket that I would like to repair, but I have no experience soldering on boards
You can see at bottom left a yellow box and a resistor. Something has burnt out in this area, and likely both will need to be replaced at a minimum
I would also need help identifying parts. The yellow box is embossed 'Tenta' and has printed on the side 'TC MEX/TENTAMKP 0.1 uf 275VAC' with some other markings obscured or damaged
Is this an achievable project?
Jesus, this isn't a slight against you OP but as an electronics engineer I feel I need to have a rant about the shoddy design here:
First of all, I have no idea what that component is dangling off the burnt-out through-hole resistor is or why it's there.
Surely it can't be a part of the temperature control loop, so I would guess it's a thermal fuse to shut off the blanket if that resistor burns because it handles power to the heating element.
If so, what THE FUCK were the designers thinking?! Couldn't afford even a small power resistor with a heatsink and a cheap thermocouple to a temp sense IC?!
Nah it'll be ok, either it burns out the resistor and the customer is not injured or the customer's house burns down. Either way no deaths, just complaints about our shitty build quality.
Second, they're using WAY too much solder for these surface mounts components.
And third, why has R16 shifted from it's pad? Bad soldering job from too much solder? Bad placement from the PNP machine? Or, god forbid, something gets hot enough to cause the solder under that resistor to start melting?
It's genuinely shocking the amount of stuff that's just being allowed to be sold these days.
If you can't get the blanket repaired OP, please consider sending this to Big Clive as he'd have a field day with this.
To the second and third issues, I think they happened because of bad settings in the wave soldering machine, and/or not prepping the board beforehand. Maybe the wave was to high, or the speed too slow. Many times you have to cover the smd components with a bit of painters tape. Even the orientation of the board on the frame can matter.
There's specific wave solder glue for smd components. Most likely all components were glued down. You can still see the off-white glue on the ICs in between the leads.
The parts that should not be soldered are usually masked off. Either with a mold or kapton tape/flexmask. Never Painters/scotch tape, since it will melt and/or burn.
Don't know about the glue thing, the smds were put by a machine, but the would move like the one in the picture if you didn't set the machine right. I can't say for sure with that resolution but I think those white things are the shiny reflections on the pins/solder. I will look into these smd glues tho, that could come handy.
And about the tape I have to say that my experience with wave soldering is not very vast, literally just one place, but they used painters tape, of the cheapest kind, and it worked just fine—no melting (it's paper?), and no burning since the solder doesn't get that hot (~200°C), the tape might stay a bit wet from the flux also idk.
It looks like a board where they indeed probably put the components on by machine, however without solder paste, since it was going through the wave solder anyway. But you would need to glue the components down then.
That's why there is so much excessive solder. If it was printed with solder paste, it wouldn't have this much solder.