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I need help replacing a Zener diode that is shorted. it connects to a NPN silicon power transistor 2SD1018. The Zener diode is between the base and emitter. I was woundering if someone was to look at the data sheet for the transistor and how the Zener is located on the PCB someone might be able to tell me the value of the Zener I’m replacing. The data sheet says BVebo (emitter to base breakdown voltage) is 5.0 volts so, I’m guessing the Zener is a 5.0 volt Zener; however, I’m just guessing.
Hello mcgagheyj, welcome to the DigiKey TechForum.
My guess is also that it would be a 5V Zener, to limit the voltage going to the base pin.
Hopefully, one of the engineer can add to this post, and help verify what Zener is being used in your circuit. Can you post pictures of the zener diode, and any numbers on it?
Is that a horizontal output transistor? It sure looks like one on that heatsink and if it is you should check out the parts in that area for over heating or cold solder joints. Horizontal output circuits are notorious for catastrophic failures and I have seen more than a few of them when I worked as a TV technician many (many) years ago. I also agree it’s likely a 5V (5.1V) zener.
Good morning, Gromit thanks for your response, this is not the horizontal output transistor. This is part of the voltage regulation circuit. This is a Toei TC-V814P Monitor from 1980’s. I have checked all surrounding components, e.g., resistor values, diodes, transistors, non-electrolytic capacitors and replaced all electricality capacitors along with the B+ pot. I have no schematics.
