I recently came across an aftermarket rapid battery charger for an old Alinco DJ-280 220 MHz Handie-Talkie. When I plugged it in, there were no signs of life. So, I looked inside and found a very crispy 1/2 watt resistor in circuit with an NPN transistor. I had to guess at the value of the resistor since I don’t have any information on this charger. Upon replacement, it was immediately clear that whatever was causing the high current was still there since the resistor was burning up again. My first guess was the NPN transistor.
I noticed that the transistor was installed in a strange way with the base and collector pins reversed. Apparently the circuit board was designed for an E-C-B pinout transistor and not this E-B-C pinout version.
I removed the transistor and tested it with a component tester. It was good but I had untwisted the leads to test it. Under a magnifying lens, you could see where the leads had obviously touched causing an arc. I reinstalled the transistor with some heat shrink tubing on the collector and the charger works again, no more smoke.
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