Quote:
Originally Posted by hardtailer
Thanks for your reply, I'll give that a go.
Can I pull pin 9 to ground directly, without a resistor inline (as R892/1kOhms is there)?
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Yes you can. The LM139 output will be shorted, but it doesn't matter, as it is an open collector output. Only a 5mA current will be drawn through the R892 resistor, which is nothing. Just short pin 9 to ground and see what happens.
You should also check and maybe replace the 74LS373 as well as the ADC. And maybe set all packages on sockets so they can easily be replaced without being soldered.
On a side note, how did you manage to remove the 40-pin MCU? Did you unsolder it as a whole with a heat gun or did you use cutting pliers to cut each pin first then unsolder and clean each pad separately?