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#1 |
diyAudio Member
Join Date: Aug 2007
Location: Sunny SC,USA 15 min south of Charlotte NC
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Hola Y'all,
My question is there a quick test to check a zener diode to see if its good or bad?? I checked a new one and it measured open in one direction and several meg ohm in the other direction and the zener in question read ~75 ohm in both directions which I suspect is bad. Your comments are welcome. Regards, Elwood
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"Lead me not into temptation...I can find it myself." |
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#2 |
diyAudio Member
Join Date: Jan 2006
Location: Johannesburg, South Africa
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Most 'Zener' diodes are in practice several avalanche diodes in series - how many depends on the voltage rating.
So both the forward and reverse voltage drop may be larger than an ordinary digital avo-meter is designed to cope with. Some old moving coil meters are better at this since they use a rather high voltage battery (some up to 15 or 22V)
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#3 |
diyAudio Moderator
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Should read as a normal diode when forward biased... ie on the diode range on a DVM it will read 0.7 ish meaning 700 mv dropped. 'tother way about and it shouldn't read as general rule for anything over a couple of volts or more but that's useless for testing accurately.
All you need is a battery of higher voltage than the zener and a restor to limit the current. Choose resistor as follows (or even better use a FET as a constant current source) R= (Vbatt-VZener)/0.010 and measure the voltage across the zener and see if it agrees with the device in question. Oh yes ![]() ![]() |
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#4 |
diyAudio Member
Join Date: Jan 2006
Location: Johannesburg, South Africa
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Only some 'zeners'. Not if it is a compound device, which many are.
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#5 |
diyAudio Member
Join Date: Aug 2007
Location: Sunny SC,USA 15 min south of Charlotte NC
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Thanks a heap you guys I guess I'll get the soldering iron out and solder and test.
Thanks again, Elwood
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"Lead me not into temptation...I can find it myself." |
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#6 |
diyAudio Member
Join Date: Aug 2007
Location: Sunny SC,USA 15 min south of Charlotte NC
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Just a quick update... replaced zener along with several trannies and my amp turns on, somewhere in this conglomeration of threads there is my B2 thread meet me there...
Thanks again, Elwood
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"Lead me not into temptation...I can find it myself." |
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