Enlarged part of the test drive transistor Q9 collector voltage of +18 V to the normal, measuring 10 feet LM339 comparator inverting input voltage of +4.6 V to normal. When the voltage is low, then change the value of resistance R31. Measuring 11 feet LM339 comparator inverting input voltage of +0.4 V to normal, when the voltage is low, the capacitor C15 leakage. LM339 comparator measuring 13 feet on the ground +0.02 V output voltage is normal, when the voltage is low, the capacitor C101 leakage, or the transistor Q8, the base B and emitter E breakdown damage, after the replacement of damaged components troubleshooting.
Also: When the diodes D17, D19, transistor Q8 parameters of failure, the capacitor C25 leakage, synchronous voltage comparator circuit, the driver amplifier is damaged, were caused by induction an “alarm does not heat” fault. This method is suitable for: United States cooker main circuit board repair circuit using monolithic LM339 reference, with 500 “list with three” test subject.
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