Electronics > Beginners
Identification of diode in a form I've never seen before
moothefish:
Can anyone tell me what the name of this style/package of diode is? I cannot for the life of me find it online, looks more like a little tantalum capacitor or something.
For context, these components are from a 1970s stereo receiver, one on each channel of the amplifier board. I've been having issues with severe hissing noise coming and going and after much troubleshooting I found that when I wiggled these diodes, the noise came and went. I did the usual of resoldering them (several times in fact) but to no avail. One was always much worse than the other and I've now noticed that one has a slight crack in the casing.
The issue is I don't have a service manual and can't find one for the life of me, so I have no idea what I would need to put in as a replacement. Anyone know what these are, or how I could find out the ratings and find a modern replacement for them? When it comes to this level of electronics, my knowledge is limited, so any help is appreciated
wraper:
I would not be so sure it's a diode. Tantalum capacitors look like diode with high forward voltage drop when measured in reverse direction. If they are leaky, voltage drop may appear lower.
moothefish:
I thought that at first, however the silkscreen on the PCB has a diode symbol and they are labelled D401 and D402, plus I couldn't seem to get any capacitance readings out of them.
magic:
Capacitance reading on diodes is only a matter of resolution, they ought to have a few pF ;)
Too young to have ever seen them :P, but some sort of zeners perhaps? What are the voltages across them, what are they connected to?
moothefish:
At a glance, I'm not entirely sure what its role in the circuit it (this is where my electronics skills are a bit crap). I've attached some photos of the board in question. Seems like they're connected between some of the smaller transistors and the main output transistors, through a resistor or two?
Please excuse the truly awful soldering, last time I touched this project was about a year ago and I promise my skills have improved a little since (though I still don't claim to be particularly good at soldering). I've noticed some joints that need touching up like the one that has an obvious hole in it lol. I'm also aware of the lifted traces but they're all making connection as far as I'm aware.
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