idy wrote: ↑30 Apr 2021, 05:21
When they say "check solder joints" they don't mean just look, but go over them again with the iron, reheat to make sure everything is connected. (not too long near the transistor, but your is socketed, sockets are often not good connections. Make sure it is firmly in place.) Often I've had things that look fine but a "cold solder" joint makes a bad connection.
That's exactly what I did, I've basically redone the whole soldering. When I check for voltages during the error, I "touch" the transistor itself, so I guess it's making contact with the socket. In any case, the error occurs in an almost timed way, I don't think joints stop connecting exactly after the same amount of time.
idy wrote: ↑30 Apr 2021, 05:21
You can't measure the value of a resistor when the power is on! And it is difficult to measure it "in circuit," but you can get some results, you have to look out for parallel R's or even a transistor that may act as a diode.
I'm not trying to measure resistance with the power on; I measure it right before powering up and straight after. R2 values does change, and you can see the value changing on the multi-meter going slowly back from 18k to 100k (already replaced that resistance and cheeked with a new one). As soon as R2 reaches back 100K, you can power on and the system starts working again (for few minutes).
idy wrote: ↑30 Apr 2021, 05:21
I would also, power off, measure for continuity between all the places that should be connected by the traces on the PCB. Sometimes a trace gets lifted or otherwise spoiled on a PCB, and although things look good, a connection is "open."
I checked the board continuity plenty of times by now, both before and after powering up. I usually test it touching resistors themselves rather than the solder joint on the back of the PCB
idy wrote: ↑30 Apr 2021, 05:21
Not sure why you took out C2.
I was trying to reduce the circuit to the smallest number of components, but still having it working (in this case, I used schematics of normal boosters, and I removed what I saw it was not present on those. It still didn't make any change...