Ok, so this seems like it’s become more of a daily thing to post about so I can’t go with what I’ve said the last couple days about us mostly working on smartphones and computers. Probably half of what I worked on today ended up being general circuit board troubleshooting and/or repair. It seems like Portland is a relatively underserved community in terms of electronics repair, or maybe we just have good SEO who knows. Anyway, today’s repair is a “Hot Tool” that would normally be used during restoration of works of art. It seems to be made by a company in Warsaw Poland and I sent them an email requesting schematics just for reference (it’s a simple enough circuit that they should not be needed).
So there’s a 1K Linear Potentiometer on the front along with the main power switch. Main power switch is clearly working because the unit does turn on without any issues, but the LED above the switch does flash or stay dark when I think it should either be flashing or solid (while heating or maintaining temperature) like most soldering irons that share a similar design language. I probed out the potentiometer after disconnecting it from the circuit and it checked out. Since it was previously cleaned I went ahead and replaced it just incase and confirmed that the same failure to achieve set temperature or hold temperature symptom persisted.
Moving on to the main board and we see that this is actually fairly built-out with quite a few passive components to test. For reference, incase anyone ends up needing them, I noted all of the component markings for transistors, voltage regulators, etc below ::
U1 : Linear Voltage Regulator : L7805CV G40UU VW CH 137
U2 : Linear Voltage Regulator : LM723CN 64208023 G VW G4 CHN
U3 : Operational Amplifier : 42N206 UA741CN CHN
U4 : Optocoupler : EL 3063 217
Q1 : Switching Triac : BT137 600E RJD1119 D2 0125
T1 : Transistor : C02 BD140-16
T2 : Transistor : BC 547B HD E
T3 : Transistor : BC 547B HD E
T4 : Transistor : BC 557B G7 E
T5 : Transistor : BC 547B HD E
No components on the rear of the board and no obviously cracked solder joints so no big concerns here for the time being.
Here is the board that has the segment display and A/D Converter mounted along with some more passive components. Since it seems to be working properly I’m not terribly worried about it either for the time being.
At long last all components have been tested on the main control board and there are a large amount of failures. Although not visibly failing both electrolytic capacitors on the board are not reading anywhere near their marked values when tested out of circuit. Tons of resistor failures as well where they are 30% - 50% off their marked values as well.
These projects are fun, but can get pretty time intensive and mentally taxing to resolve. Someone has to do it though! Just make sure you bring in your smartphone for a display replacement and your laptop for a solid-state drive installation and/or memory upgrade to increase performance so that we can keep repairing this weirder stuff since it’s basically break-even and done after hours at the moment!